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3,800 | Out-of-hospital cardiac arrest in a child without overt cardiac disease: emergency department management. | This case report describes the successful resuscitation of a 7-year-old girl who had no previous history of cardiac disease other than one episode of syncope. She developed ventricular fibrillation for 10 min. External chest compressions, early defibrillation and orotracheal intubation were used with a successful outcome. |
3,801 | Results from the first 12 months of a fire first-responder program in Australia. | We aimed to reduce response times and time to defibrillation for out-of-hospital cardiac arrest patients through fire first-responders equipped with automatic external defibrillators (AEDs). The fire first-responders were added as an extra tier to the existing two-tired ambulance response.</AbstractText>This prospective controlled trial set in Melbourne, Australia, consisted of a control area (277 km2, population density 2343/km2-ambulance only dispatch) and a pilot area (171 km2, population density 2290/km2-ambulance and fire first-responder dispatch). The main outcome measures were time to emergency medical service (EMS) arrival at scene for all cardiac arrest patients and time to defibrillation for cardiac arrest patients presenting in ventricular fibrillation (VF). The study participants were patients who suffered a cardiac arrest of presumed cardiac aetiology for which a priority 0 emergency response was activated. A total of 268 patients were located in the control area and 161 in the pilot (intervention) area.</AbstractText>The mean response time to arrival at scene was reduced by 1.60 (95% CI 1.21, 1.99) min, P < 0.001. A large reduction in prolonged responses (> or = 10 min) to cardiac arrests was also observed in the pilot area (2%) compared with the control area (18%), chi = 23.19, P < 0.001. Mean time to defibrillation was reduced by 1.43 (95% CI 0.11, 2.98) min, P = 0.068.</AbstractText>The results from this study suggest that fire officers can be successfully trained in the use of AEDs and can integrate well into a medical response role. The combined response of ambulance and fire personnel significantly reduced the response interval and reduced time to defibrillation. This suggests that in appropriate situations other agencies could be considered for involvement in co-ordinated first-responder programs.</AbstractText> |
3,802 | Employing vasopressin during cardiopulmonary resuscitation and vasodilatory shock as a lifesaving vasopressor. | Epinephrine during cardiopulmonary resuscitation (CPR) is being discussed controversially due to its beta-receptor mediated adverse effects such as increased myocardial oxygen consumption, ventricular arrhythmias, ventilation-perfusion defect, postresuscitation myocardial dysfunction, ventricular arrhythmias and cardiac failure. In the CPR laboratory simulating adult pigs with ventricular fibrillation or postcountershock pulseless electrical activity, vasopressin improved vital organ blood flow, cerebral oxygen delivery, resuscitability, and neurological recovery better than did epinephrine. In paediatric preparations with asphyxia, epinephrine was superior to vasopressin, whereas in both paediatric pigs with ventricular fibrillation, and adult porcine models with asphyxia, combinations of vasopressin and epinephrine proved to be highly effective. This may suggest that a different efficiency of vasopressors in paediatric vs. adult preparations; and different effects of dysrhythmic vs. asphyxial cardiac arrest on vasopressor efficiency may be of significant importance. Whether these theories can be extrapolated to humans is unknown at this point in time. In patients with out-of-hospital ventricular fibrillation, a larger proportion of patients treated with vasopressin survived 24 h compared with patients treated with epinephrine; during in-hospital CPR, comparable short-term survival was found in groups treated with either vasopressin or epinephrine. Currently, a large trial of out-of-hospital cardiac arrest patients being treated with vasopressin vs. epinephrine is ongoing in Germany, Austria and Switzerland. The new CPR guidelines of both the American Heart Association, and European Resuscitation Council recommend 40 U vasopressin intravenously, and 1 mg epinephrine intravenously as equally effective for the treatment of adult patients in ventricular fibrillation; however, no recommendation for vasopressin was made to date for adult patients with asystole and pulseless electrical activity, and paediatrics due to lack of clinical data. When adrenergic vasopressors were unable to maintain arterial blood pressure in patients with vasodilatory shock, continuous infusions of vasopressin ( approximately 0.04 to approximately 0.1 U/min) stabilised cardiocirculatory parameters, and even ensured weaning from catecholamines. |
3,803 | Inappropriate shock delivery due to ventricular double detection with a biventricular pacing implantable cardioverter defibrillator. | This report describes a patient with advanced heart failure, pronounced intraventricular conduction delay, and ventricular tachycardias who underwent implantation of a multisite pacing ICD. Pacing leads were placed in the right atrium, right ventricular apex, and to the left ventricular posterior wall via a coronary sinus vein. The system proved to have correct sensing and pacing function in an atrial synchronized biventricular pacing mode and an appropriate detection of ventricular fibrillation. However, 1 month after implantation the patient received an inappropriate shock delivery due to double detection of ventricular premature beats. The inherent detection problem of dual ventricular sensing is discussed. |
3,804 | Mapping the organization of atrial fibrillation with basket catheters. Part I: Validation of a real-time algorithm. | The authors proposed a real-time algorithm to quantify AF organization from multielectrode basket catheter (MBC) recordings. The algorithm is based on a fast method to estimate the number of points along the baseline of a single bipolar electrogram (number of occurrences, NO). They have already proven this parameter to be effective at discriminating AF organization according to Wells' criteria. Special attention has been paid to ventricular far-field artifacts, as they proved they can significantly bias the degree of organization. To fulfill the constraints of a real-time application, a ventricular blanking procedure was implemented and validated. Bipolar electrograms were obtained from MBC in the right atrium in 17 informed patients with chronic AF. The results of NO computations were displayed as three-dimensional color-coded maps of organization by interpolating the measurements obtained at the locations of catheter bipoles. The proposed method allows real-time estimation of the organization of the atrial electrograms according to Wells' criteria. The estimation has a temporal resolution of 2 seconds, is robust to far-field ventricular artifacts, and interpolates the data available to furnish a single global map of the entire atrium. Further studies devoted to the analysis of individual and common patterns of the regional distribution of AF organization are needed to assess the usefulness of this approach for electrophysiological studies and therapeutic applications. |
3,805 | The prognostic significance of atrial arrhythmias recorded early after cardioversion for atrial fibrillation. | In a substantial number of patients, AF recurs after successful electrical cardioversion. The purpose of this study was to investigate if the atrial arrhythmias recorded immediately after cardioversion are associated with the risk of recurrence of the arrhythmia and to compare the prognostic significance of this parameter with that of other established risk factors. In a series of 71 patients, the risk factors for recurrence of AF during the first year after successful electrical cardioversion were analyzed. A new parameter that was investigated was the frequency of atrial premature beats and the presence of runs of supraventricular tachycardia in the Holter recording started immediately after the cardioversion. Age, left atrial size, left ventricular systolic function, duration of the arrhythmia before cardioversion, underlying cardiac disease, or medication taken were not found to be predictive of recurrence of the arrhythmia. However, the natural logarithm of the number of atrial premature complexes per hour of the Holter recording in the 37 patients in whom AF recurred was higher compared to that of the 34 patients who maintained sinus rhythm (P < 0.0005). The same was true if only the first 6 hours of the recording were analyzed (P < 0.0005). There was a trend for more frequent arrhythmia recurrence if runs of supraventricular tachycardia were present. The finding of > 10 atrial premature complexes per hour in the recording had a relative risk of 2.57 (1.51-4.37), a positive predictive accuracy of 76.5%, and a negative predictive accuracy of 70.3% for subsequent arrhythmia recurrence. We can conclude that frequent (> 10/hour) atrial premature complexes in the Holter recording after electrical cardioversion for AF is a significant risk factor for recurrence of the arrhythmia. |
3,806 | Prospective evaluation of catheter ablation in patients with implantable cardioverter defibrillators and multiple inappropriate ICD therapies due to atrial fibrillation and type I atrial flutter. | The high incidence of inappropriate therapies due to drug refractory supraventricular tachycardia remains a major unsolved problem of the ICD. Most of the inappropriate therapies for supraventricular tachycardia are caused by AF and type I atrial flutter with rapid ventricular response. The purpose of this prospective study was to determine the usefulness of AVN modulation or ablation for rapid AF and ablation of the tricuspid annulus-inferior vena cava (TA-IVC) isthmus for type I atrial flutter in ICD patients with frequent inappropriate ICD interventions. Eighteen consecutive patients were enrolled in this study. Twelve patients received a mean of 34 +/- 36 antitachycardia pacing (ATP) and 41 +/- 32 shock therapies for rapid AF during 49 +/- 39 months, and 6 patients a mean of 111 +/- 200 ATP and 11 +/- 8 shock therapies for type I atrial flutter during 52 +/- 37 months preceding ablation procedure. Modification of the AVN was successful in 10 (83%) of 12 AF patients, in 2 (17%) patients ablation of the AVN was performed. A complete TA-IVC isthmus block was achieved in 5 (83%) of 6 atrial flutter patients. Three (25%) AF patients had 11 +/- 24 recurrences of ATP and 0.4 +/- 1.1 shock therapies for rapid AF during 15 +/- 7 months. None of the atrial flutter patients had recurrences of inappropriate therapies for type I atrial flutter during 14 +/- 8 months, but two (33%) patients had inappropriate ICD therapies for type II atrial flutter or rapid AF. There was an overall mean incidence of 18 +/- 22 inappropriate ICD therapies per 6 months before and 4 +/- 9 per 6 months after the ablation procedure (P < 0.05). In conclusion, radiofrequency catheter modification or ablation of the AVN for rapid AF and ablation for atrial flutter type I are demonstrated to be highly effective in the majority of ICD patients with drug refractory multiple inappropriate ICD therapies. |
3,807 | Fatal form of phaeochromocytoma presenting as acute pyelonephritis. | We report the case of a young man who presented with a clinical picture of acute pyelonephritis. Within 3 h of admission, the patient developed acute respiratory distress associated with tachycardia and shock, and he was transferred to the intensive care unit. Mechanical ventilation of the lungs and symptomatic treatment were started immediately. Abdominal ultrasound revealed the presence of an adrenal tumour with central necrosis indicating a probable phaeochromocytoma. There was no sign of pyelonephritis. Ventricular fibrillation followed by asystole occurred soon after admission. The suddenness of the patient's death did not allow time for further investigation and therapy. The severity of the clinical signs was probably related to a massive release of catecholamines because of necrosis of the tumour, which may have been worsened by the diagnostic procedures performed to investigate the clinical symptoms and signs of acute pyelonephritis. |
3,808 | Spontaneous right ventricular outflow tract tachycardia in a patient with Brugada syndrome. | We report the case of a 28-year-old man with no structural heart disease, who exhibited clearly augmented ST segment elevation in the right precordial leads, followed by induction of spontaneous right ventricular outflow tract tachycardia with intravenous administration of Class IA antiarrhythmic drugs. The electrophysiologic mechanism of this tachycardia was thought to be triggered activity due to delayed afterdepolarizations. Due to the existence of substrates that were similar to Brugada syndrome combined with right ventricular outflow tract tachycardia, this case may represent a subtype of Brugada syndrome. |
3,809 | Electrocardiographic analysis of ectopic atrial activity obscured by ventricular repolarization: P wave isolation using an automatic 62-lead QRST subtraction algorithm. | Atrial activity on the surface ECG during premature beats and supraventricular arrhythmias frequently is obscured by the superimposed QRST complex of the previous cardiac cycle. This study examines the performance of a newly developed automatic QRST subtraction algorithm to isolate ectopic P waves from the preceding T-U wave.</AbstractText>The 62-lead ECG recordings were obtained during (1) sinus rhythm and programmed right atrial stimulation in 12 patients (group A); and (2) sinus rhythm and atrial premature beats, atrial tachycardia, or paroxysmal atrial fibrillation in 5 patients (group B). Pacing in group A patients was conducted at a slow drive cycle length to generate an ectopic P wave not obscured by the previous QRST complex and by delivering single premature extrastimuli at progressively shorter coupling intervals to produce an ectopic P wave obscured by the upsloping (early T-U wave), peak (middle T-U wave), and downsloping component of the T-U wave (late T-U wave). All ectopic P waves in group B patients were concealed by the preceding T-U wave. Automatic QRST subtraction was attained using an adaptive template constructed from averaged QRST complexes (mean 83 +/- 25 complexes) obtained during sinus rhythm (groups A and B) or atrial overdrive pacing (group A). P wave integral maps subsequently were computed, visually compared, and mathematically correlated. A high correspondence in spatial map pattern was observed between integral maps of "nonobscured" and previously "obscured" paced P waves obtained in group A patients (mean r = 0.88 +/- 0.07) as well as between integral maps of two to three previously obscured P waves with the same atrial arrhythmia morphology obtained in group B patients (mean r = 0.94 +/- 0.05). Improved morphologic P wave replication in group A patients was acquired when concealment occurred in the early (mean r = 0.90 +/- 0.08) or late part of the T-U wave (mean r = 0.90 +/- 0.06) as opposed to the middle T-U wave (mean r = 0.85 +/- 0.07) (P = NS and P < 0.05 for early vs middle and late vs middle T-U wave, respectively).</AbstractText>This novel automatic 62-lead QRST subtraction algorithm enables discrete isolation of T-U wave obscured ectopic atrial activity on the surface ECG while retaining the intricate spatial detail in P wave morphology. Future clinical application of the algorithm may enable improved ECG localization of focal triggers of paroxysmal atrial fibrillation, atrial tachycardia, and the atrial insertion of accessory pathways.</AbstractText> |
3,810 | Repolarization abnormalities detected by magnetocardiography in patients with dilated cardiomyopathy and ventricular arrhythmias. | Abnormal repolarization is one of the acknowledged mechanisms leading to malignant ventricular arrhythmias. We used a novel magnetocardiographic technique to investigate the role of inhomogeneous repolarization in patients with nonischemic dilated cardiomyopathy prone to sustained ventricular arrhythmias.</AbstractText>Forty-nine dilated cardiomyopathy patients were studied, 18 with a history of sustained ventricular tachycardia (n = 6) or ventricular fibrillation (n = 12) and 31 with no ventricular arrhythmias. The magnetocardiogram was registered and QT apex and QT end intervals were determined by a computer algorithm. Inhomogeneity of repolarization was characterized with indices describing QT apex and QT end dispersion, and T wave end duration. In addition, time-domain late fields of the QRS complex in magnetocardiography and QT dispersion in 12-lead ECG were determined. T wave end was longer in the arrhythmia group in patients with sinus rhythm (87 +/- 15 msec vs 73 +/- 12 msec; P = 0.005) and in those not having bundle branch block. Magnetocardiographic late fields of the QRS complex were not different between groups. QT apex and end dispersion on magnetocardiography or 12-lead ECG showed no difference.</AbstractText>Prolongation of the end part of the T wave revealed by magnetocardiography is related to malignant ventricular arrhythmias in dilated cardiomyopathy. The results suggest that abnormal repolarization rather than delayed conduction underlies the arrhythmias in this disease.</AbstractText> |
3,811 | Endothelin system in human persistent and paroxysmal atrial fibrillation. | Activation of the endothelin system is an important compensatory mechanism that is activated during left ventricular dysfunction. Whether this system plays a role at the atrial level during atrial fibrillation (AF) has not been examined in detail. The purpose of this study was to investigate mRNA and protein expression levels of the endothelin system in AF patients with and without concomitant underlying valve disease.</AbstractText>Right atrial appendages of 36 patients with either paroxysmal or persistent AF were compared with 36 controls in sinus rhythm. The mRNA amounts of pro-endothelin-1 (pro-ET-1), endothelin receptor A (ET-A), and endothelin receptor B (ET-B) were studied by semiquantitative polymerase chain reaction. Protein amounts of the receptors were investigated by slot-blot analysis. mRNA amounts of pro-ET-1 were increased (+40%; P = 0.002) only in AF patients with underlying valve disease. ET-A and ET-B receptor protein amounts were significantly reduced in patients with paroxysmal AF (-39% and -47%, respectively) and persistent AF with underlying valve disease (-28% and -30%, respectively) and in persistent AF without valve disease (-20% and -40%, respectively). ET-A mRNA expression was unaltered in paroxysmal and persistent AF, whereas ET-B mRNA was reduced by 30% in persistent AF with (P < 0.001) or without (P = 0.04) valve disease, but unchanged in paroxysmal AF.</AbstractText>Substantial changes in gene expression of the endothelin system were observed in human atria during AF, especially in the presence of underlying valve disease. Alterations in endothelin expression associated with AF could play a role in the pathophysiology of AF and the progression of underlying heart disease.</AbstractText> |
3,812 | Initial clinical experience with a new arrhythmia detection algorithm in dual chamber implantable cardioverter defibrillators. | Inappropriate therapy, due to poor discrimination of supraventricular tachycardia (SVT) from ventricular tachycardia (VT) remains a major problem in patients with an implantable cardioverter defibrillator (ICD). Theoretically, the addition of atrial sensing in discrimination algorithms should improve this differentiation. The aim of the study is to evaluate the performance of a new tachycardia discrimination algorithm, SMART Detection.</AbstractText>Twenty-six patients received a non-thoracotomy ICD system (Phylax AV, Biotronik, Germany). All documented spontaneous arrhythmia episodes were analyzed. During a mean follow-up of 8 months, a total number of 139 events with stored electrograms were recorded in 12 patients. The final diagnosis was ventricular fibrillation (VF) or polymorphic VT (n=20), monomorphic VT (n=69), SVT (n=26), other ventricular arrhythmia (n=3) and T wave oversensing (n=21). In 6 episodes a dual tachycardia was present. Considering SVT episodes, inappropriate therapy occurred in 2 cases of atrial flutter due to stable ventricular rate (<30 ms), 1 case of atrial tachycardia and 2 cases of sinus tachycardia due to a sudden onset (> 10%).</AbstractText>With the SMART Detection algorithm, discrimination of VT from SVT achieved a sensitivity of 100%, with an accuracy of 95.6% for all ventricular arrhythmias. In the case of SVT, the algorithm appropriately detected and inhibited therapy in 88% of atrial fibrillation.</AbstractText> |
3,813 | Dual-coil vs single-coil active pectoral implantable defibrillator lead systems: defibrillation energy requirements and probability of defibrillation success at multiples of the defibrillation energy requirements. | The aim of the study was to compare the defibrillation energy requirements and the probability of successful defibrillation at multiples of the minimum defibrillation energy requirements in active pectoral implantable defibrillators with single- and dual-coil lead systems.</AbstractText>Eighty-three consecutive patients undergoing implantation of an active pectoral cardioverter-defibrillator were randomized to receive a dual- or single-coil lead system. Defibrillators of two manufacturers with a fixed tilt biphasic defibrillation waveform were used. Defibrillation energy requirements were determined using a step-down defibrillation testing protocol. According to the randomization protocol, the patients were assigned to three additional consecutive defibrillation attempts during device implantation and during pre-discharge testing of either 1.0, 1.5 or 2.0 times the determined defibrillation energy requirement. Patients presenting defibrillation energy requirements > 15 J were excluded from analysis. Eighty of 83 patients (96%) completed the study protocol. Three patients were excluded due to elevated defibrillation energy requirements. The defibrillation energy requirements in the dual- and single-coil patient groups were 8.0 +/- 3.6 J and 8.4 +/- 3.7 J (ns), respectively. A comparable percentage of study patients showed defibrillation energy requirements <10 J (dual-coil: 88% vs single-coil: 83%). Defibrillation impedance was significantly different (dual-coil: 50 +/- 5.8 Ohm; single-coil: 39.8 +/- 4.2 Ohm). Regarding the probabilities of successful defibrillation, there were no significant differences between the two patient groups. The probabilities of defibrillation at the three multiples of the defibrillation energy requirement using a dual- and single-coil lead system were 82, 89.7 and 93.6 and 77.8, 94.1 and 95.8%, respectively (P=0.88, P=0.42, P=0.62, respectively).</AbstractText>Dual- and single-coil active pectoral defibrillator systems show no difference in defibrillation energy requirements and no difference in the probability of successful defibrillation at multiples of the minimum defibrillation energy requirement. The use of more simplified defibrillator lead systems may contribute to a future lead design focusing on improvement in lead durability.</AbstractText> |
3,814 | Dobutamine stress echocardiography response of asymptomatic patients with diabetes. | This study investigated the role of dobutamine stress echocardiography for the silent diagnosis of myocardial ischemia in a diabetic population. Results from the stress test were compared between diabetic and nondiabetic groups.</AbstractText>Forty-nine diabetics and 63 consecutive nondiabetics underwent dobutamine stress echocardiography between April and December 1999, to check for new regional wall-motion abnormalities. A single operator, using the same echograph with tissue harmonic imaging in each case, performed all the examinations, using the same techniques.</AbstractText>Significant coronary artery disease was detected in 9% of asymptomatic diabetics. Dynamic left ventricular obstruction was observed in 59% of the diabetic population and only 22% in the nondiabetic population. One patient suffered an adverse event (fast atrial fibrillation) during the stress test. Cardiac frequency at the beginning and end of the stress test differed significantly between the two populations.</AbstractText>Dobutamine stress echocardiography allows for detection of silent myocardial ischemia. In the diabetic population, we describe, for the first time under dobutamine infusion, a great number of dynamic left ventricular obstructions.</AbstractText> |
3,815 | Perception and documentation of arrhythmias after successful radiofrequency catheter ablation of accessory pathways. | Some patients continue to have palpitations in spite of successful ablation of Wolff-Parkinson-White (WPW) syndrome. Recurrence of accessory pathways as well as unrelated arrhythmias may explain the symptoms.</AbstractText>We followed 194 consecutive patients after successful radiofrequency catheter ablation of overt (147) or concealed (47) WPW syndrome. The mean duration of symptoms was 16 +/- 13 years. Atrial fibrillation was documented in 54 patients (24%) prior to ablation. 185 patients responded to a questionnaire 24 +/- 12 months after ablation.</AbstractText>The physical well-being was improved in 94%, unchanged in 5%, and deteriorated in 1%. However, 76 patients (39%) reported arrhythmia symptoms, in 40 patients causing pharmacological treatment (14 patients) and/or continued contact with their doctor. The underlying arrhythmias were orthodromic tachycardia (10), atrial fibrillation (12), premature beats (12), atrial flutter (1), and ventricular tachycardia (1), while in four patients no explanation was found. Minor symptoms in the other 36 patients were explained by premature beats in 29, while unexplained in 7. All patients with atrial fibrillation after ablation had atrial fibrillation before ablation. Ten relapses of WPW syndrome occurred: eight were known before the time of the questionnaire, two were confirmed at transesophageal atrial stimulation.</AbstractText>94% patients with a long history of tachyarrhythmias due to the WPW syndrome reported improved physical well-being after ablation, but palpitations were common during a 2-year follow-up period; 8% continued to use pharmacological antiarrhythmic treatment. Five percent had symptomatic relapses and in 6% atrial fibrillation episodes reoccurred, i.e., in half of those who had atrial fibrillation before ablation.</AbstractText> |
3,816 | Predicting the recurrence of ventricular tachyarrhythmias from T-wave alternans assessed on antiarrhythmic pharmacotherapy: a prospective study in patients with dilated cardiomyopathy. | Microvolt T-wave alternans (TWA) has been proposed as a useful index to identify patients at risk of ventricular tachyarrhythmias. Recent studies have demonstrated that antiarrhythmic drugs, such as amiodarone and procainamide, decrease the prevalence of TWA. In this study, we tested whether TWA in patients on antiarrhythmic pharmacotherapy significantly predicts the recurrence of ventricular tachyarrhythmias in patients with dilated cardiomyopathy.</AbstractText>To evaluate the ability to predict the recurrence of ventricular tachyarrhythmias, determinate TWA and left ventricular ejection fraction (LVEF) were prospectively assessed in 49 patients with ischemic or nonischemic dilated cardiomyopathy on antiarrhythmic pharmacotherapy for sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). The pharmacotherapy consisted of class I (17 patients), III (29 patients), and IV (3 patients) antiarrhythmic drugs. The study endpoint was the first recurrence of sustained VT or VF on treatment during the follow-up period.</AbstractText>TWA was positive on antiarrhythmic pharmacotherapy in 30 patients (61%). During a follow-up of 13 +/- 11 months, the sustained VT or VF recurred in 21 of the 41 patients (51%) with available follow-up data. The sensitivity of TWA and LVEF for predicting recurrence of ventricular tachyarrhythmias was 76 and 38%, specificity was 60 and 70%, positive predictive value was 67 and 57%, and negative predictive value was 71 and 52%. Kaplan-Meier event-free analysis revealed that TWA was a significant risk stratifier (P = 0.02), whereas LVEF was not.</AbstractText>This prospective study suggests that TWA significantly predicts the recurrence of ventricular tachyarrhythmias, even on antiarrhythmic pharmacotherapy, in patients with dilated cardiomyopathy. TWA may also be a useful marker for evaluating the efficacy of antiarrhythmic drugs for ventricular tachyarrhythmias.</AbstractText> |
3,817 | Qt dispersion and mortality in the elderly. | The prognostic value of QT interval dispersion measured from a standard 12-lead electrocardiogram (ECG) in the general population is not well established. The purpose of the present study was primarily to assess the value of QT interval dispersion obtained from 12-lead ECG in the prediction of total, cardiac, stroke, and cancer mortality in the elderly.</AbstractText>A random population sample of community-living elderly people (n = 330, age > or = 65 years, mean 74 +/- 6 years) underwent a comprehensive clinical evaluation, laboratory tests, and 12-lead ECG recordings.</AbstractText>By the end of the 10-year follow-up, 180 subjects (55%) had died and 150 (45%) were still alive. Heart rate corrected QT (QTc) dispersion had been longer in those who had died than in the survivors (75 +/- 32 ms vs 63 +/- 35 ms, P = 0.01). After adjustment for age and sex in the Cox proportional hazards model, prolonged QTc dispersion (> or = 70 msec) predicted all-cause mortality (relative risk [RR] 1.38, 95% confidence interval [CI] 1.02-1.86) and particularly stroke mortality (RR 2.7, 95% CI 1.29-5.73), but not cardiac (RR 1.38, 95% CI 0.87-2.18) or cancer (RR 1.51, 95% CI 0.91-2.50) mortality. After adjustment for age, sex, body mass index, blood pressure, blood glucose and cholesterol concentrations, functional class, history of cerebrovascular disease, diabetes, smoking, previous myocardial infarction, angina pectoris, congestive heart failure, medication, left ventricular hypertrophy on ECG, presence of atrial fibrillation and R-R interval, increased QTc dispersion still predicted stroke mortality (RR 3.21, 95% CI 1.09-9.47), but not total mortality or mortality from other causes. The combination of increased QTc dispersion and left ventricular hypertrophy on ECG was a powerful independent predictor of stroke mortality in the present elderly population (RR 16.52, 95% CI 3.37-80.89). QTcmin (the shortest QTc interval among the 12 leads of ECG) independently predicted total mortality (RR 1.0082, 95% CI 1.0028-1.0136, P = 0.003), cardiac mortality (RR 1.0191, 95% CI 1.0102-1.0281, P < 0.0001) and cancer mortality (RR 1.0162, 95% CI 1.0049-1.0277, P = 0.005).</AbstractText>Increased QTc dispersion yields independent information on the risk of dying from stroke among the elderly and its component, QTcmin, from the other causes of death.</AbstractText> |
3,818 | Right heart catheterization and cardiac complications in patients undergoing noncardiac surgery: an observational study. | Right heart catheterization (RHC) is commonly performed before high-risk noncardiac surgery, but the benefit of this strategy remains unproven.</AbstractText>To evaluate the relationship between use of perioperative RHC and postoperative cardiac complication rates in patients undergoing major noncardiac surgery.</AbstractText>Prospective, observational cohort study.</AbstractText>Tertiary care teaching hospital in the United States.</AbstractText>Patients (n = 4059 aged >/=50 years) who underwent major elective noncardiac procedures with an expected length of stay of 2 or more days between July 18, 1989, and February 28, 1994. Two hundred twenty one patients had RHC and 3838 did not.</AbstractText>Combined end point of major postoperative cardiac events, including myocardial infarction, unstable angina, cardiogenic pulmonary edema, ventricular fibrillation, documented ventricular tachycardia or primary cardiac arrest, and sustained complete heart block, classified by a reviewer blinded to preoperative data.</AbstractText>Major cardiac events occurred in 171 patients (4.2%). Patients who underwent perioperative RHC had a 3-fold increase in incidence of major postoperative cardiac events (34 [15.4%] vs 137 [3.6%]; P<.001). In multivariate analyses, the adjusted odds ratios (ORs) for postoperative major cardiac and noncardiac events in patients undergoing RHC were 2.0 (95% confidence interval [CI], 1.3-3.2) and 2.1 (95% CI, 1.2-3.5), respectively. In a case-control analysis of a subset of 215 matched pairs of patients who did and did not undergo RHC, adjusted for propensity of RHC and type of procedure, patients who underwent perioperative RHC also had increased risk of postoperative congestive heart failure (OR, 2.9; 95% CI, 1.4-6.2) and major noncardiac events (OR, 2.2; 95% CI, 1.4-4.9).</AbstractText>No evidence was found of reduction in complication rates associated with use of perioperative RHC in this population. Because of the morbidity and the high costs associated with RHC, the impact of this intervention in perioperative care should be evaluated in randomized trials.</AbstractText> |
3,819 | In-vivo testing of digital cellular telephones in patients with implantable cardioverter-defibrillators. | To investigate the susceptibility of implantable cardioverter defibrillators to electromagnetic interference generated by digital cellular telephones, functioning in both international transmission technologies: the Global System for Mobile Communication (GSM) and the Digital Cellular System (DCS 1800).</AbstractText>In 36 patients with transvenous implantable cardioverter defibrillators from two manufacturers (Medtronic and Guidant/CPI), cellular telephones with different levels of minimal and maximal power output were tested in the transmitting and receiving mode. Evaluation was performed in activated implantable defibrillators during spontaneous cardiac activity and continuous VVI or DDD pacing to assess possible electromagnetic interference. In two patients, appropriateness of ventricular fibrillation detection and therapy was judged during telephone testing. There was no damage, reprogramming, inappropriate shock therapy or pacing inhibition during the tests. In seven pre-pectoral Medtronic implantable defibrillators, transient electromagnetic interference caused 19 erroneous sensing events, when the operating phone was held in close vicinity to the programmer head. These 'pseudo-oversensing' events, which did not result in logging of arrhythmia episodes in the device counter, were interpreted as an adverse interaction between the telephone and the programming device.</AbstractText>Digital cellular telephones do not represent a risk to Medtronic and Guidant/CPI recipients of the specific implantable defibrillator models herein tested.</AbstractText>Copyright 2001 The European Society of Cardiology.</CopyrightInformation> |
3,820 | Elevations in antidiuretic hormone and aldosterone as possible causes of fluid retention in the Maze procedure. | Reduced levels of atrial natriuretic peptide (ANP) has been suggested as a cause of fluid retention after combined Maze and valvular surgery. This study aimed to assess hormonal activation in the perioperative setting of isolated Maze procedures.</AbstractText>Changes in ANP, brain natriuretic peptide (BNP), antidiuretic hormone (ADH), aldosterone, and angiotensin II were measured in 16 patients (mean age 53+/-9 years) without concomitant heart disease undergoing the Maze (III) procedure. Ten matched patients (mean age 56+/-9 years) undergoing multivessel coronary artery bypass grafting served as controls. Measurements with hemodynamic correlates were obtained at baseline and after ventricular pacing (100 stimulations/minute), directly preoperatively, postoperatively and the first postoperative day. Weight gain and diuretic requirements were recorded.</AbstractText>The major differences in hormonal response were significantly higher plasma levels of ADH (Maze preoperative 1.1+/-0.4, postoperative 24.9+/-16.7 pmol/L; controls preoperative 1.1+/-0.1, postoperative 3.7+/-3.5 pmol/L) and aldosterone (Maze preoperative 106+/-94, postoperative 678+/-343 pmol/L; controls preoperative 124+/-79, postoperative 171+/-93 pmol/L) in the Maze group on the first postoperative day (p < 0.001). Preoperative baseline plasma levels of ANP and pulmonary capillary wedge pressures (PCWP) were higher in the Maze group but this difference was abolished by pacing, and postoperatively, ANP levels changed in parallel to the PCWP in both groups. Diuretic requirements were significantly higher in the Maze group.</AbstractText>Substantial increases in ADH and aldosterone were observed after the Maze procedure, indicating these hormones as important determinants in postoperative fluid retention. The role for ANP in this setting may be a less prominent than previously reported.</AbstractText> |
3,821 | [Conduction disturbances and cardiac arrhythmias in myotonic dystrophy--diagnosis and clinical significance in adult populations]. | Myotonic dystrophy (DM) is the most frequent adult form of muscular dystrophy. The clinical presentation consists of both muscular and systemic involvement. One of the main causes of high mortality is sudden cardiac death due to tachyarrhythmias and conduction disturbances. The knowledge of cardiovascular complications is very important because of diagnostic and therapeutic possibilities. The main cardiological complications of DM are arrhythmias associated with the destruction of the conduction system. The main electrocardiographic changes (prolongation of the P-R interval, left anterior hemiblock, increased QRS duration) reflect destruction of the His-Purkinje system and may progress very rapidly, leading to death due to Stokes-Adams attacks. The most frequent tachyarrhythmias are atrial and ventricular extrasystoles, atrial flutter and fibrillation, as well as ventricular tachycardia, that can be a cause of sudden death. The mechanisms underlying ventricular arrhythmias are conduction disturbances, prolongation of the QT interval, impaired coronary reserve and autonomic function. A common type of tachycardia seen in patients with DM is that originating from the branches of the bundle of His (bundle-branch re-entry). Risk stratification (in respect of cardiological complications) is possible on the basis of electrophysiological studies, clinical symptoms and a family history. Invasive electrophysiological investigation and implantation of a pacemaker may be indicated in patients with electrocardiographic features of a significant disease of the conduction system. Multicentre clinical trials assessing the efficacy of this therapeutic strategy are underway. |
3,822 | Intravenous magnesium sulfate versus diltiazem in paroxysmal atrial fibrillation. | Drugs currently available for the acute treatment of paroxysmal atrial fibrillation have significant limitations. We assessed the safety and effectiveness of intravenous magnesium sulfate versus diltiazem therapy in patients with prolonged episodes of paroxysmal atrial fibrillation.</AbstractText>In a prospective randomized trial, 46 symptomatic patients presenting with paroxysmal atrial fibrillation were given intravenous magnesium sulfate (n=23) or diltiazem (n=23) therapy. Primary outcome measures were effects on ventricular rate control and proportion of patients restored to sinus rhythm at 6 h after initiation of treatment.</AbstractText>There were no differences in baseline characteristics between the two groups. Both forms of treatment were well tolerated, with no adverse clinical events. Both drugs had similar efficacy in reducing the ventricular rate at the first hour of treatment (P<0.05) with a tendency toward a further decrease during infusion times of 2 (P<0.01), 3, 4, 5 and 6 h, respectively (P<0.001). However, at the end of the 6-h treatment period, restoration of sinus rhythm was observed in a significantly higher proportion of patients in the magnesium group compared with the diltiazem group [13 of 23 patients, (57%), versus five of 23 patients, (22%), P=0.03].</AbstractText>Magnesium sulfate favorably affects rate control and seems to promote the conversion of long lasting episodes of paroxysmal atrial fibrillation to sinus rhythm, representing a safe, reliable and cost-effective alternative treatment strategy to diltiazem.</AbstractText> |
3,823 | The relation between transmitral early filling wave deceleration time and the recovery of atrial contractility after electrical cardioversion of atrial fibrillation. | Electrical cardioversion of atrial fibrillation (AF) to sinus rhythm is associated with transient left atrial dysfunction and this phenomenon may lead to thrombus formation and embolic stroke. Delay of atrial mechanical function recovery may be related to ventricular diastolic function.</AbstractText>This study examined the effects of left ventricular diastolic function as well as the multiple clinical factors on the recovery of atrial systolic function after cardioversion for atrial fibrillation.</AbstractText>A total of 44 patients (28 male, 16 female, 61+/-18 years) with chronic AF (> or =1 month) underwent electrical cardioversion. Deceleration time of early filling wave (pre-CV EDT) on transmitral inflow obtained by using Doppler echocardiography before cardioversion and serial transmitral inflow Doppler variables were recorded through a 1 week study period in all patients. Various clinical (age, gender, the duration of AF) and echocardiographic variables (pre-CV EDT, left atrial dimension, left ventricular ejection fraction) were tested for an association with peak atrial filling wave velocity (VA) on day 1, 3 and 7 after cardioversion.</AbstractText>EDT measured before cardioversion had a strong linear correlation with peak VA on every echocardiographic evaluation after cardioversion (Regression coefficient (R)=0.69, P<0.001; R=0.78, P<0.001 and R=0.83, P<0.001, on day 1, day 3 and day 7, respectively). The effect of left ventricular ejection fraction on peak VA was weaker than those of EDT. The duration of AF showed an inverse association with the recovery of atrial function, but this lost on multivariate analysis. None of the other parameters significantly correlated with peak VA after cardioversion.</AbstractText>The recovery of atrial mechanical function after cardioversion, as assessed by peak VA on transthoracic Doppler echocardiography is mainly associated with the left ventricular diastolic function as measured by EDT, whereas the left ventricular systolic function relatively a small effect on this outcome. The duration of AF does not have any association with peak VA, possibly if it is chronic.</AbstractText> |
3,824 | Alpha-linolenic acid and cardiovascular diseases. | The intake of saturated fat was postulated to be the main environmental factor for coronary heart disease. It was also postulated that the noxious effects of saturated fatty acids (FA) was primarily through the increase in serum cholesterol. Nevertheless intervention trials either in coronary patients or even in primary prevention did not observe significant reduction in cardiac mortality, especially sudden death, when the diet was markedly enriched in linoleic acid (LA), the most efficient FA to lower serum cholesterol. In intervention trials, It is only when the diet was enriched in n-3 FA, especially alphalinolenic acid (ALA) that cardiac death was reduced. Studies in animals as well as in vitro on myocytes in culture, have shown that ALA was preventing ventricular fibrillation, the chief mechanism of cardiac death. Furthermore, studies in rats have observed that among n-3 FA, ALA, the precursor of the n-3 family, may be more efficient to prevent ventricular fibrillation than eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In addition it was demonstrated that ALA was the main FA lowering platelet aggregation, an important step in thrombosis, i. e. non fatal myocardial infarction and stroke. Thus, without side effects, a higher intake of ALA (2g / day) with a ratio of 5/1 for LA/ALA, could possibly constitute a nutritional answer to the main cause of morbidity and mortality in industrialized countries. |
3,825 | Efficacy of dofetilide in the treatment of atrial fibrillation-flutter in patients with reduced left ventricular function: a Danish investigations of arrhythmia and mortality on dofetilide (diamond) substudy. | In patients with left ventricular dysfunction, atrial fibrillation and flutter (AF and AFl, respectively) are common arrhythmias associated with increased morbidity and mortality. The present study investigated the potential of dofetilide in AF-AFl patients with left ventricular dysfunction to restore and maintain sinus rhythm, which might reduce mortality and hospitalizations.</AbstractText>In the Danish Investigations of Arrhythmia and Mortality ON Dofetilide (DIAMOND) studies, 506 patients were in AF-AFl at baseline. Over the course of study, cardioversion occurred in 148 (59%) dofetilide- and 86 (34%) placebo-treated patients. In these patients, the probability of maintaining sinus rhythm for 1 year was 79% with dofetilide versus 42% with placebo (P<0.001). Dofetilide had no effect on all-cause mortality, but restoration and maintenance of sinus rhythm was associated with significant reduction in mortality (risk ratio [RR], 0.44; 95% CI, 0.30 to 0.64; P<0.0001). In addition, dofetilide therapy was associated with a significantly lower risk ratio versus placebo for either all-cause (RR, 0.70; 95% CI, 0.56 to 0.89; P</=0.005) or congestive heart failure (RR, 0.69; 95% CI, 0.51 to 0.93; P</=0.02) rehospitalization.</AbstractText>Dofetilide is safe and increases the probability of obtaining and maintaining sinus rhythm in patients with structural heart disease. The present study suggests that restoration of sinus rhythm is associated with improved survival.</AbstractText> |
3,826 | Evaluation and treatment of other arrhythmic causes of syncope in children and adolescents with an apparently normal heart: Wolff-Parkinson-White syndrome and right ventricular cardiomyopathy. | Syncope could be a symptom of tachyarrhythmias related to the Wolff-Parkinson-White syndrome, or the consequence of the ventricular tachycardias seen in patients with Arrhythmogenic Right Ventricular Cardiomyopathy. Syncope should be considered the consequence of atrial fibrillation or flutter, with rapid conduction over the accessory atrioventricular connection in Wolff-Parkinson-White syndrome, and these patients are at risk of presenting with ventricular fibrillation and sudden death. Radiofrequency ablation of the anomalous, accessory connection, which can be performed with high success and low complication rates, should be the first line of treatment for symptomatic children and adolescents with Wolff-Parkinson-White. Arrhythmogenic Right Ventricular Cardiomyopathy is a rare disorder of the cardiac muscle affecting predominantly, although not exclusively, the right ventricle. Clinical presentation varies from asymptomatic cases to patients with severe symptoms related to life-threatening arrhythmias, right ventricular failure, or congestive heart failure with involvement of both ventricles. The clinical diagnosis is difficult. A set of major and minor criteria has been proposed to help to identify patients with this disease. Without an identified cause, the treatment of patients with Arrhythmogenic Right Ventricular Cardiomyopathy is symptomatic. Medical management of the associated congestive heart failure, pharmacologic treatment of the arrhythmias, radiofrequency ablation and implantable cardioverter-defibrillator therapy should all be considered. |
3,827 | PAI-I 4G/5G polymorphism and sudden cardiac death in patients with coronary artery disease. | The 4G/5G polymorphism of the plasminogen activator inhibitor type I (PAI-I) gene is involved in coronary artery disease (CAD), with the highest risk in 4G/4G homozygotes. The role of PAI-I polymorphism in patients suffering from CAD and history of sudden cardiac death (SCD) has not been addressed yet. We studied the frequency distribution of the PAI-I gene to test the hypothesis that the 4G/4G genotype favors myocardial ischemia and, even in the absence of acute infarction, promotes SCD in patients with CAD.</AbstractText>The PAI-I 4G/5G genotypes and PAI-I antigen plasma levels were determined in 97 patients with CAD and a history of SCD treated with an implantable cardioverter defibrillator (ICD) (defibrillator group) comparing to 113 patients with CAD but no history of SCD (control group).</AbstractText>The defibrillator group consisted of significantly more 4G/4G homozygotes and higher PAI-I levels than the control group (44% vs. 24%, 173+/-41 vs. 144+/-49 ng/ml; P<.01). The carriers of 4G allele had a significantly higher risk for SCD (odds ratio (OR) 1.9) with the highest risk in the 4G/4G genotype (OR 3.6, P<.01).</AbstractText>These results suggest that the PAI-I 4G/4G genotype is associated with SCD in patients suffering from CAD.</AbstractText> |
3,828 | Assessment of LV systolic function in atrial fibrillation using an index of preceding cardiac cycles. | The clinical assessment of left ventricular (LV) systolic function during atrial fibrillation (AF) is unreliable and difficult because of beat-to-beat variability. We evaluated an index for the estimation of LV systolic function in AF that is based on the relationship between the preceding (R-R1) and prepreceding (R-R2) R-R intervals. LV Doppler stroke volume (SV), ejection fraction (EF), peak aortic flow rate (AoF) and the maximum value of the first derivative of the LV pressure curve (dP/dt(max)) were evaluated in 13 healthy open-chest dogs during triggered AF. All parameters showed a significantly strong positive linear relationship with the ratio of R-R1/R-R2 (r = 0.65, 0.74, 0.75, and 0.70 for SV, EF, AoF, and dP/dt(max), respectively). The calculated value of LV systolic parameters at R-R1/R-R2 = 1 in the linear regression line showed a good relationship and an agreement with the measured average value of the parameter over all cardiac cycles (SV, 12.1 vs. 12.8 ml; EF, 49.6 vs. 51.2%; AoF, 1.37 vs. 1.48 l/min; and dP/dt(max), 2,323 vs. 2,454 mmHg/s). Using the LV systolic parameters estimated at R-R1/R-R2 = 1 in the linear regression line allows the LV contractile function to be accurately and reproducibly evaluated during AF and obviates the less-reliable process of averaging multiple cardiac cycles. |
3,829 | Trends and outcomes in the hospitalization of older Americans for cardiac conduction disorders or arrhythmias, 1991-1998. | To identify epidemiological trends and measure outcomes in elderly patients hospitalized for cardiac conduction disorders or arrhythmias.</AbstractText>Review of the standard 5% samples of the Medicare Provider Analysis and Review Files to characterize 144,512 discharges from 1991 through 1998 in which the principal diagnosis was a conduction disorder or arrhythmia, using the corresponding Enrollment Databases for denominator data.</AbstractText>Short-stay hospitals in the United States.</AbstractText>Medicare beneficiaries age 65 and older in the standard 5% sample.</AbstractText>Diagnosis-specific trends and rates; discharges by year; cumulative age-, race-, and sex-specific discharge rates; mean length of stay in hospital and in intensive care; mean Medicare reimbursement to the hospital; case-fatality rate in hospital; discharge destinations of patients discharged alive.</AbstractText>Annual hospitalizations for sinoatrial node dysfunction, atrial flutter, atrial fibrillation, or ventricular fibrillation increased more rapidly than did the elderly Medicare beneficiary population. Hospitalizations with a principal diagnosis of ventricular extrasystoles or asystole showed steep secular declines. Discharge rates for sinoatrial node dysfunction, a group of rhythms with a nonsinus pacemaker, atrial fibrillation, Mobitz I, or complete atrioventricular block all increased steeply and continuously with patient age. In contrast, discharge rates for atrial flutter or ventricular tachycardia or fibrillation peaked among 75- to 84-year-old patients. White men were at uniquely high risk of hospitalization for atrial flutter or ventricular tachycardia or fibrillation, and, among the white majority, men had higher discharge rates than women for nine of the 11 commonest rubrics. Whites, particularly white women, had the highest discharge rates for atrial fibrillation. Blacks, especially black women, were at disproportionate risk for hospitalization for the group of nonsinus pacemaker rhythms. Diagnosis-specific mean resource costs were strongly correlated with each other and with mean Medicare reimbursement but not with case-fatality rate.</AbstractText>Medicare claims data demonstrated striking differences among and within diagnoses of heart blocks or arrhythmias in terms of the populations at greatest risk for hospitalization. This variation should be explored further to generate and test hypotheses about differential causation or delivery of care.</AbstractText> |
3,830 | Comparison of defibrillation thresholds using monodirectional electrical vector versus bidirectional electrical vector. | Currently, two main lead configurations are used for implantable cardioverter-defibrillators (ICD). One generates a monodirectional electrical vector by using the can surface as an active part (hot can) together with a right ventricular defibrillation coil. The other one (TRIAD) produces a bidirectional electrical vector by adding a proximal defibrillation electrode on the same lead. The purpose of this prospective study was to determine whether there is a difference between these configurations in terms of the acute defibrillation threshold (DFT). The secondary objective was to evaluate the possible sequential effect of successive arrhythmia induction and defibrillation shocks on the final DFT value.</AbstractText>In 44 patients (37 males, 7 females, mean age 59.18 +/- 12.05 years; mean ejection fraction 35.21 +/- 11.69%), a Hot Can Ventak family ICD (Guidant, St. Paul, MN, USA) was implanted in a left pectoral pocket. During the implant procedure, step-down to failure DFT testing was performed twice in each patient using the two different above-mentioned configurations: the bidirectional and the monodirectional. The first configuration to be tested was determined by a 1:1 randomization by center.</AbstractText>The step-down DFT protocol was followed in 35 patients. The average DFT was 8.6 +/- 4.0 J for TRIAD and 10.4 +/- 4.3 J for the monodirectional (p = 0.009) lead configuration; this represents a 16.3% decrease in the DFT using a bidirectional configuration. Furthermore, no relationship between the final DFT and the number of ventricular fibrillation inductions and shocks received was observed, confirming the secondary objective.</AbstractText>Compared to the monodirectional electrical vector, the bidirectional electrical vector is clearly more beneficial for the patient.</AbstractText> |
3,831 | In patients with chronic atrial fibrillation and left ventricular systolic dysfunction, restoration of sinus rhythm confers substantial benefit. | To evaluate the benefit of sinus rhythm (SR) restoration in patients with chronic controlled atrial fibrillation (AF) and left ventricular systolic dysfunction (LVSD).</AbstractText>Prospective case-control study on the short-term outcome (6 to 9 months) of clinical and echocardiographic variables following attempted cardioversion.</AbstractText>Outpatient clinic of a university hospital.</AbstractText>Fifteen men and 5 women, ranging in age from 40 to 76 years, who had chronic controlled (mean [+/- SD] ventricular rate, 82 +/- 10 beats/min) AF and left ventricular fractional shortening (LVFS) of < 28% at baseline. Control was provided by retrospective paired echocardiographic examinations of six AF patients, plus the study cases with potentially unsuccessful cardioversion or early recurrence of AF.</AbstractText>Attempt to restore SR with amiodarone or electrical countershock.</AbstractText>Conversion was attained in 17 patients, but AF recurred early in 4 patients, 3 of whom had proven ischemic LVSD. In the 13 patients with sustained SR, LVFS increased from 20 +/- 4% to 31 +/- 6% (p < 0.0001). In contrast, no changes were detected in the control group (n = 13). This improvement was paralleled by decreases in left ventricular (LV) end-diastolic dimension (from 55 +/- 7 to 51 +/- 6 mm; p = 0.014), LV mass (from 181 +/- 28 to 159 +/- 37 g; p = 0.015), and left atrial diameter (from 45 +/- 9 mm to 42 +/- 7; p = 0.003). A marked decrease in heart rate (from 82 +/- 9 to 64 +/- 5 beats/min; p < 0.0001) and a reduction in New York Heart Association functional class (from 2.3 +/- 0.9 to 1.2 +/- 0.4; p = 0.0007) also were observed in patients with sustained SR but not among subjects in the control group.</AbstractText>Even when adequate control of the ventricular rate has been achieved, the LV function of patients with chronic AF greatly improves after restoration and maintenance of SR.</AbstractText> |
3,832 | Progression to chronic atrial fibrillation after pacing: the Canadian Trial of Physiologic Pacing. CTOPP Investigators. | This study examined the effect of physiologic pacing on the development of chronic atrial fibrillation (CAF) in the Canadian Trial Of Physiologic Pacing (CTOPP).</AbstractText>The role of physiologic pacing to prevent CAF remains unclear. Small randomized studies have suggested a benefit for patients with sick sinus syndrome. No data from a large randomized trial are available.</AbstractText>The CTOPP randomized patients undergoing first pacemaker implant to ventricular-based or physiologic pacing (AAI or DDD). Patients who were prospectively found to have persistent atrial fibrillation (AF) lasting greater than or equal to one week were defined as having CAF. Kaplan-Meier plots for the development of CAF were compared by log-rank test. The effect of baseline variables on the benefit of physiologic pacing was evaluated by Cox proportional hazards modeling.</AbstractText>Physiologic pacing reduced the development of CAF by 27.1%, from 3.84% per year to 2.8% per year (p = 0.016). Three clinical factors predicted the development of CAF: age > or =74 years (p = 0.057), sinoatrial (SA) node disease (p < 0.001) and prior AF (p < 0.001). Subgroup analysis demonstrated a trend for patients with no history of myocardial infarction or coronary disease (p = 0.09) as well as apparently normal left ventricular function (p = 0.11) to derive greatest benefit.</AbstractText>Physiologic pacing reduces the annual rate of development of chronic AF in patients undergoing first pacemaker implant. Age > or =74 years, SA node disease and prior AF predicted the development of CAF. Patients with structurally normal hearts appear to derive greatest benefits.</AbstractText> |
3,833 | Transient left ventricular apical ballooning without coronary artery stenosis: a novel heart syndrome mimicking acute myocardial infarction. Angina Pectoris-Myocardial Infarction Investigations in Japan. | To determine the clinical features of a novel heart syndrome with transient left ventricular (LV) apical ballooning, but without coronary artery stenosis, that mimics acute myocardial infarction, we performed a multicenter retrospective enrollment study.</AbstractText>Only several case presentations have been reported with regard to this syndrome.</AbstractText>We analyzed 88 patients (12 men and 76 women), aged 67 +/- 13 years, who fulfilled the following criteria: 1) transient LV apical ballooning, 2) no significant angiographic stenosis, and 3) no known cardiomyopathies.</AbstractText>Thirt-eight (43%) patients had preceding aggravation of underlying disorders (cerebrovascular accident [n = 3], epilepsy [n = 3], exacerbated bronchial asthma [n = 3], acute abdomen [n = 7]) and noncardiac surgery or medical procedure (n = 11) at the onset. Twenty-four (27%) patients had emotional and physical problems (sudden accident [n = 2], death/funeral of a family member [n = 7], inexperience with exercise [n = 6], quarreling or excessive alcohol consumption [n = 5] and vigorous excitation [n = 4]). Chest symptoms (67%), electrocardiographic changes (ST elevation [90%], Q-wave formation [27%] and T-wave inversion [97%]) and elevated creatine kinase (56%) were found. After treatment of pulmonary edema (22%), cardiogenic shock (15%) and ventricular tachycardia/fibrillation (9%), 85 patients had class I New York Heart Association function on discharge. The LV ejection fraction improved from 41 +/- 11% to 64 +/- 10%. Transient intraventricular pressure gradient and provocative vasospasm were documented in 13/72 (18%) and 10/48 (21%) of the patients, respectively. During follow-up for 13 +/- 14 months, two patients showed recurrence, and one died suddenly.</AbstractText>A novel cardiomyopathy with transient apical ballooning was reported. Emotional or physical stress might play a key role in this cardiomyopathy, but the precise etiologic basis still remains unclear.</AbstractText> |
3,834 | Public access defibrillation: a shocking idea? | Currently, survival from out-of-hospital cardiac arrest in the United Kingdom is poor. Ambulance response standards require that an ambulance reach 75 per cent of cardiac arrests within 8 min. But a short time to defibrillation from the onset of collapse is a key predictor of outcome from out-of-hospital cardiac arrest. The Department of Health has recently implemented a lay responder defibrillation programme, with the aim of shortening this time interval for victims in public places. This initiative utilizes automated external defibrillators (AEDs), which provide written and recorded voice prompts to minimize training requirements and errors in use. Lay responder AED programmes with very short response times have reported survival to discharge rates of up to 53 per cent for patients presenting in ventricular fibrillation (VF). This compares well with the results of a meta-analysis that reported a survival rate of only 6.4 per cent for traditional defibrillator-equipped ambulance systems. The annual incidence of out-of-hospital cardiac arrest in England is 123 per 100,000 population. Approximately half of these present in VF, and could benefit from an AED programme. But only 16 per cent of cardiac arrests occur in a public place. It has been calculated that there are approximately 5,000 instances of VF in public places each year in England. If half of these patients can be reached and administered a first shock within 4 min of their collapse, an additional 400 victims may survive each year. Given the current investment by the DoH of 2 million pounds, this suggests a cost per life saved of approximately 505 pounds over a 10 year period. |
3,835 | Left ventricular relaxation abnormality is detectable by analysis of the relaxation time constant in patients with atrial fibrillation. | Left ventricular (LV) contractility is constantly changing during atrial fibrillation (AF), which is dependent on the force-interval relationships. However, no information has been available on LV relaxation in patients with both AF and impaired LV systolic function. LV pressure was measured with a catheter-tipped micromanometer and the time constant of isovolumic LV pressure decline (tau(bf)) was calculated with best exponential fitting from more than 10 consecutive beats. Patients with AF (5 with mitral valvular disease, 6 with idiopathic dilated cardiomyopathy, and 1 with no underlying disease) were subdivided into 2 groups: group A, with ejection fraction (EF) <0.5 (n=7); and group B, with EF > or =0.5 (n=5). Linear correlation coefficients (r) between tau and RR2, RR2/RR1, LV peak systolic pressure (peak LVP) were calculated. Although tau did not show a discrepancy between the 2 groups, tau(bf) correlated better with RR2/RR1 only in the group A patients. The relation between tau and peak LVP showed a good correlation with a steep slope (R, Deltatau/Deltapeak LVP) only in the group A patients (accentuated afterload-dependence). R was significantly different between the 2 groups. Thus, a beat-to-beat analysis of tau may be a practical and feasible way for detecting LV relaxation abnormality in patients with AF. |
3,836 | Reversible impairment of left and right ventricular systolic and diastolic function during short-lasting atrial fibrillation in patients with an implantable atrial defibrillator: a tissue Doppler imaging study. | AF with a fast ventricular response may cause ventricular mechanical impairment, though whether short-lasting AF with satisfactory rate control may affect ventricular function is unknown. This study investigated if prompt cardioversion by an implantable atrial defibrillator (IAD) may prevent left (LV) and right ventricular (RV) systolic and diastolic dysfunction. Ten patients (mean age 61 +/- 9 years, 8 men) with paroxysmal AF without structural heart disease who received an IAD were studied by echocardiography and tissue Doppler imaging (TDI) for both ventricles. Measurements were made during baseline sinus rhythm and at 1-minute, 20-minute, 4-hour, and 1-week postcardioversion of an episode of spontaneous AF. The occurrence of AF and the ventricular rate were monitored at 2-hour intervals by the device. There were 50 episodes of AF with a mean duration of 8.8 +/- 8.9 days (2 hours to 37 days). There was no difference in M-mode measured LV fractional shortening and ejection fraction between baseline sinus rhythm and after cardioversion. However, the TDI derived myocardial systolic velocity (TDI-S) was significantly lower at 1-minute postcardioversion and was normalized at 1 week in both LVs (baseline: 5.7 +/- 1.8, 1 minute: 4.2 +/- 1.0, 20 minutes: 4.3 +/- 0.9, 4 hours: 4.8 +/- 1.0, 1 week: 5.5 +/- 1.8 cm/s; P < 0.005 when comparing 1 minute and 20 minutes to baseline; P < 0.05 when comparing 4 hour to baseline) and RV (baseline: 10.4 +/- 2.1, 1 minute: 7.8 +/- 1.4, 20 minutes: 8.1 +/- 1.2, 4 hours: 9.2 +/- 1.5, 1 week: 10.0 +/- 2.0 cm/s; P < 0.005 when comparing 1 minute, 20 minutes, and 4 hours to baseline). For diastolic function, transmitral Doppler study showed a decrease in early filling velocity at 1 minute (P < 0.05) and 20 minutes (P < 0.005), which was normalized at 4 hours. There was no change in transtricuspid Doppler flow. However, TDI derived myocardial early filling velocity was decreased in the LV (baseline: 6.0 +/- 2.8, 1 minute: 5.4 +/- 2.3, 20 minutes: 5.4 +/- 2.1, 4 hours: 6.1 +/- 2.2, 1 week: 5.8 +/- 1.7 cm/s; P < 0.05 when comparing 1 minute and 20 minutes to baseline) and RV (baseline: 8.9 +/- 3.5, 1 minute: 7.9 +/- 3.3, 20 minutes: 8.1 +/- 3.3, 4 hours: 8.5 +/- 2.9, 1 week: 8.4 +/- 3.5 cm/s; P < 0.05 when comparing 1 minute to baseline). AF of a longer duration (> 48 hours) resulted in a more depressed TDI-S in LV (> 48 hours: 4.2 +/- 1.0, < or = 48 hours: 5.3 +/- 1.3 cm/s; P < 0.01). Shocks in sinus rhythm did not affect any of the above echocardiographic parameters. Therefore, despite adequate rate control, short-lasting AF impairs systolic and diastolic function in both ventricles, which improves gradually after cardioversion. Early restoration of sinus rhythm by an IAD minimizes ventricular dysfunction. TDI is a sensitive tool to assess early systolic and diastolic dysfunction. |
3,837 | Relation between paroxysmal atrial fibrillation and left ventricular diastolic function in patients with acute myocardial infarction. | The relation between left ventricular filling pattern and the occurrence of paroxysmal atrial fibrillation was evaluated using Doppler echocardiography in a prospective series of 157 patients with acute myocardial infarction. Paroxysmal atrial fibrillation after acute myocardial infarction was often associated with a higher restrictive filling pattern. |
3,838 | External biphasic defibrillators. Should you catch the wave? | Introduced about five years ago, external biphasic defibrillators have attracted a lot of attention. The biphasic waveforms they use have been shown in some studies to be more successful than standard monophasic waveforms in terminating ventricular fibrillation and ventricular tachycardia. But with this apparent step forward comes confusion: A variety of biphasic waveforms are available, and each defibrillator supplier is making claims for the superiority of its particular waveform. Are biphasic waveforms really better than monophasic? Is any one biphasic waveform preferable to another? What does the clinical literature say about this technology? This article answers those and other pressing questions about biphasic defibrillators. |
3,839 | Successful ventricular defibrillation by the selective sodium-hydrogen exchanger isoform-1 inhibitor cariporide. | Sodium-hydrogen exchanger isoform-1 (NHE-1) activation worsens functional myocardial abnormalities associated with ischemia and reperfusion. We hypothesize that these abnormalities may limit cardiac resuscitation from ventricular fibrillation (VF) and investigated whether NHE-1 inhibition with the benzoylguanidine derivative cariporide could improve resuscitability, postresuscitation myocardial function, and short-term survival in isolated heart and intact rat models of VF. Methods and Results-- In the isolated rat heart, VF was induced for 25 minutes. Perfusion was interrupted for the initial 10 minutes and restarted at 10% of baseline flow for the remaining 15 minutes (simulating chest compression). Cariporide ameliorated ischemic contracture, prevented postresuscitation diastolic dysfunction, and favored earlier return of contractile function. In the intact rat, cariporide, injected into the right atrium before chest compression was started (after 6 minutes of untreated VF), prompted spontaneous defibrillation between minutes 7 and 9 of chest compression in 6 of 8 rats. In contrast, electrical defibrillation was required in each of 8 control rats after completion of a predetermined 16-minute interval of VF. After resuscitation, cariporide-treated rats had less ventricular ectopic activity and normalized their hemodynamic function faster. Electrical defibrillation was then timed in control rats to match the time when spontaneous defibrillation occurred in cariporide-treated rats. With comparable VF duration, postresuscitation hemodynamic dysfunction was ameliorated by cariporide, but only when more severe ischemia was modeled by prolongation of the interval of untreated VF from 6 to 10 minutes.</AbstractText>NHE-1 inhibition may represent a novel and remarkably effective intervention for resuscitation from VF.</AbstractText> |
3,840 | Optical mapping of ventricular defibrillation in isolated swine right ventricles: demonstration of a postshock isoelectric window after near-threshold defibrillation shocks. | Investigators who studied ventricular defibrillation by use of optical mapping techniques failed to observe an initial defibrillation event (isoelectric window or quiescent period) shown by electrode mapping studies. This discrepancy has important implications for the mechanisms of defibrillation. The purpose of the present study was to demonstrate an optical equivalent of an isoelectric window after a near-threshold defibrillation shock. Methods and Results-- We studied 10 isolated, perfused swine right ventricles. Upper limit of vulnerability was determined by shocks on T waves. A 50% probability of successful defibrillation (DFT50) was determined with an up-down algorithm. Immediately after unsuccessful defibrillation shock, new wavefronts were generated. When the shock strength was low, immediate reinitiation of reentry and ventricular fibrillation might occur without a postshock isoelectric window. However, if the shock strength was within 50 V of DFT50 (near-threshold), a synchronized activation occurred, followed by organized repolarization that ended 64+/-18 ms after shock. After a period of quiescence (18+/-24 ms), activation recurred 83+/-33 ms after shock and reinitiated ventricular fibrillation. Similar patterns of activation, including a quiescent period, were observed after shock was applied on the T wave of the paced beat that induced ventricular fibrillation. Upper limit of vulnerability correlated well with DFT50.</AbstractText>In isolated swine right ventricles, an optical equivalent of an isoelectric window exists after near-threshold defibrillation shocks. These findings support the idea that a near-threshold defibrillation shock terminates all activation wavefronts but fails to halt ventricular fibrillation because the same shock reinitiates ventricular fibrillation after an isoelectric window.</AbstractText> |
3,841 | [Ventricular arrhythmias induced by appropriate antibradycardia pacing in patients with implantable defibrillators]. | The induction of ventricular arrhythmias by appropriate antibradycardia ventricular pacing in patients with implantable cardioverter defibrillators has been reported in only a few cases. The aim of this study was to assess the incidence, characteristics and management of these episodes.</AbstractText>The follow-up records of 180 patients with implantable cardioverter defibrillators with intracardiac electrogram storage were reviewed. Pacing induced episodes were defined as those occurring immediately after an appropriate paced stimulus in a patient with sporadic paced beats. We assessed the number and type of episodes, mode of onset, therapy administered and the efficacy of different prevention measures.</AbstractText>Pacing induced episodes were found in 9 patients (5%). Seven received device administered therapy which was effective in all cases. One to 95 episodes were observed per patient, of which 138 were monomorphic ventricular tachycardias and 20 polymorphic ventricular tachycardia/ventricular fibrillation episodes. All were induced by a paced ventricular beat after a post-extrasystolic pause or after long RR intervals during atrial fibrillation. Pacing induced arrhythmias were prevented by changing the pacing rate or hysteresis in 3 out of 6 patients and by decreasing the stimulus energy in 3 out of 3. Antibradycardia pacing function was disabled in 4 patients.</AbstractText>Ventricular arrhythmias induced by appropriate antibradycardia ventricular pacing are relatively common in patients with implantable cardioverter defibrillators. Effective prevention can be achieved in most cases by changing the pacing rate or the pacing stimulus energy, however in selected cases the antibradycardia function may be disabled.</AbstractText> |
3,842 | [Prognosis of patients admitted to the coronary or intensive care unita after an out of hospital episode of sudden death]. | Out of hospital sudden death constitutes a major sanitary problem. Early diagnosis and treatment are considered as the most important factors related with short term prognosis. However, there is little information about the outcome of patients admitted to the hospital after a successful recovery from an episode of sudden death outside the hospital. The objective of this study was to analyze the prognosis of patients who initially recovered after an episode of out-of-hospital cardiac arrest and who were admitted to the coronary or intensive care unit.</AbstractText>The clinical characteristics and outcome of 110 consecutive patients admitted to the coronary and intensive care units after an episode of extrahospital sudden death, who initially recovered with success, were retrospectively studied.</AbstractText>A total of 33 (30%) patients were discharged alive and without severe neurological damage, 67 (61%) patients died before discharge from hospital and 77 (70%) died or presented severe and permanent neurological damage. The latter group versus those who survived was older (63.6 +/- 13.5 vs 55.2 +/- 12.6 years old; p < 0.006) and had a longer delay in the beginning of cardiopulmonary resuscitation (8.3 vs 2.8 min.; p < 0.01). Mortality or severe neurological damage rate was higher in the group of those who had asystolia than in those with ventricular fibrillation in the first ECG (84% vs 55%), in those who arrived to the hospital unconscious (73.7% vs 15.4%) and in those who arrived in functional class IV (81% vs 16.6%).</AbstractText>Up to 30% of the patients admitted after an episode of extrahospital cardiac arrest were discharged alive and without severe neurological damage. Advanced age, functional class IV and the delay of cardiopulmonary resuscitation are related to a unfavorable outcome.</AbstractText> |
3,843 | Out-of-hospital cardiac arrest in Hong Kong. | To evaluate the effectiveness of the local emergency medical services system in resuscitation of out-of-hospital cardiac arrest and identify areas for improvement.</AbstractText>This was a prospective descriptive study of adults with nontraumatic out-of-hospital cardiac arrest treated in the three accident & emergency departments that serve the whole of Hong Kong Island from March 15, 1999, to October 15, 1999. Patient characteristics, circumstances of cardiac arrest, final outcomes, and response times of the ambulance service were recorded according to the Utstein style.</AbstractText>Three hundred twenty patients were included. There was male predominance, and the mean age was 71.5 years. The majority of cardiac arrests occurred at patients' homes. In 57.5% of cases the arrest was not witnessed. The bystander cardiopulmonary resuscitation (CPR) rate was 15.6%. The most common electrocardiographic (ECG) rhythm at scene was asystole. Ventricular fibrillation or pulseless ventricular tachycardia constituted 14.1%. The average call to dispatch interval was 1.04 minutes. The average call to CPR interval was 9.82 minutes. The average total prehospital interval was 27.55 minutes. The overall immediate survival rate was 14.1% and the rate of survival to hospital discharge was 1.25%.</AbstractText>The prognosis of out-of-hospital cardiac arrest in Hong Kong was dismal. Every link in the chain of survival has to be improved.</AbstractText> |
3,844 | The locations of nonresidential out-of-hospital cardiac arrests in the City of Pittsburgh over a three-year period: implications for automated external defibrillator placement. | To determine the locations of nonresidential out-of-hospital cardiac arrests (OHCAs) in the City of Pittsburgh and to determine whether there are "high-risk" locations that might benefit from placement of automated external defibrillators (AEDs).</AbstractText>This was a retrospective case review of paramedic calls for OHCA over a three-year period, in a mid-sized northeastern city. Cardiac arrests that were traumatic or for which the patients were dead on arrival (DOA) or had advanced directives for no resuscitation were excluded. Cardiac arrests that occurred in a public location (i.e., not a private residence) were categorized.</AbstractText>A total of 971 OHCAs occurred in the City of Pittsburgh from January 1, 1997, to December 31, 1999. Of these, 575 (59%) occurred in private residences, and 396 (41%) occurred in nonresidential locations. Fifteen locations had at least one cardiac arrest per year for three years, accounting for 166 (43%) of the total nonresidential OHCAs. Twelve locations had two arrests during the three-year period, accounting for 24 (6%) of the total nonresidential OHCAs. One hundred ninety-four locations had a single episode of cardiac arrest, accounting for 51% of the OHCAs. Nursing homes and dialysis centers accounted for 178 (94%) OHCAs in the 27 locations that had two or more cardiac arrests. A local sports/events complex (Three Rivers Stadium) was the only other single location to have more than two cardiac arrests in the three-year study period, with a total of three. However, events at this complex are routinely staffed by paramedics equipped with defibrillators.</AbstractText>The majority of nonresidential OHCAs occur as singular, isolated events. Other than nursing homes and dialysis centers, there were no identifiable high-risk locations for nonresidential OHCA within the City of Pittsburgh.</AbstractText> |
3,845 | Cardiac arrest management. | Approximately 1,000 people in the United States suffer cardiac arrest each day, most often as a complication of acute myocardial infarction (AMI) with accompanying ventricular fibrillation or unstable ventricular tachycardia. Increasing the number of patients who survive cardiac arrest and minimizing the clinical sequelae associated with cardiac arrest in those who do survive are the objectives of emergency medical personnel. In 1990, the American Heart Association (AHA) suggested the chain of survival concept, with four links--early access, cardiopulmonary resuscitation (CPR), defibrillation, and advanced care--as the way to approach cardiac arrest. The recently published International Resuscitation Guidelines 2000 of the AHA have addressed advances in our understanding of the chain of survival. While the chain of survival concept has withstood a decade of scrutiny, there are only a few scientifically rigorous research studies that support changes in prehospital patient care. Additional research efforts carried out in the prehospital setting are needed to support the concepts included in the chain of survival for cardiac arrest patients. Participants at the second Turtle Creek Conference, a meeting of experts in the field of emergency medicine held in Dallas, Texas, on March 29-31, 2000, discussed these and other issues associated with prehospital emergency care in the cardiac arrest patient. This paper addresses a number of the issues associated with each of the links of the chain of survival, the evidence that exists, and what should be done to achieve the clinical evidence needed for true clinical significance. Also included in this paper are the consensus statements developed from small discussion groups held after the main presentation. These comments provide another perspective to the problems and to possible approaches to deal with them. |
3,846 | Inappropriate discharges from an intravenous implantable cardioverter defibrillator due to T-wave oversensing. | This report describes the clinical management of 2 patients with ventricular fibrillation (VF) who received inappropriate shocks from an implantable cardioverter defibrillator (ICD) due to T-wave oversensing. Cardiac sarcoidosis was confirmed as the underlying heart disease in 1 patient and idiopathic dilated cardiomyopathy in the other. Within 2 months after ICD implantation, both patients received several inappropriate shocks during sinus rhythm. Stored electrograms showed decreased R-wave amplitudes and increased T-wave amplitudes. The ICD sensed both R- and T-waves as ventricular activation, which met the rate criteria for VF treatment. Reprogramming the sensing threshold in association with administration of a drug to slow the heart rate decreased the incidence of the inappropriate shocks in both patients, but these palliative measures did not completely suppress the inappropriate shocks. To avoid T-wave oversensing, the repositioning or adding of a sensing lead is required. The potential risk of T-wave oversensing in ICD patients who have small R-wave amplitudes should be recognized. |
3,847 | The D allele of the angiotensin-converting enzyme gene and reperfusion-induced ventricular arrhythmias in patients with acute myocardial infarction. | The renin-angiotensin system may play a pivotal role in reperfusion ventricular arrhythmias (RVA). The purpose of this study was to investigate the association between angiotensin-converting enzyme (ACE) gene polymorphism and RVA in patients with acute myocardial infarction (AMI) in a case-control study. Patients who had undergone successful coronary intervention for AMI were enrolled (n= 127, male/female: 97/30, mean age, 62.6 years). The incidence of RVA was continuously monitored by ECG at a coronary care unit. The severity of ventricular arrhythmias was evaluated in terms of the Lown's grade and patients with a high risk of ventricular arrhythmias that may cause sudden cardiac death (Lown's grade > or =2) within 5 h of coronary intervention were defined as cases (n=59), and otherwise as controls (n=68). A receiver operating characteristic curve was used to determine the discriminatory ability of continuous variables and to produce dummy variables for use in a logistic regression analysis. Cases had a significantly higher body mass index, higher maximal levels of serum creatine kinase, and a shorter time preceding coronary intervention than controls. The severity of coronary atherosclerosis was similar between the 2 groups. The frequency distribution of ACE genotypes in cases differed from that in controls (II/ID/DD: 22.0%/52.6%/25.4% vs 44.1%/41.4%/14.7%, p<0.05, by the Mantel-Haenzel chi-square test). The ACE-D allele had additive and dominant effects with regard to the occurrence of significant ventricular arrhythmias after adjusting for other risk factors. The ACE-D allele may play a pivotal role in sudden cardiac death in patients with AMI. |
3,848 | Atrial Flutter. | Atrial flutter (AFl) is an arrhythmia resulting from reentry in a macroreentrant circuit, most commonly in the right atrium. Typical AFl uses the narrow isthmus of right atrial tissue between the tricuspid valve annulus and the inferior vena cava orifice as part of the macroreentrant circuit. The treatment of AFl is directed toward achieving the following four goals. 1) In the presence of AFl, adequate rate control is required, which can be achieved in most but not all patients by oral or intravenous digoxin, calcium channel blockers, or beta-blockers, alone or in combination. 2) Anticoagulation with warfarin should be considered in patients with recurrent AFl, especially those over 70 years of age, and those with a history of atrial fibrillation, stroke, or structural heart disease. 3) Conversion to sinus rhythm can be achieved in up to 70% of patients with intravenous ibutilide, but this should be reserved for patients with either normal hearts or only mild left ventricular dysfunction. Direct-current cardioversion is nearly 100% effective and is ideal for patients with left ventricular dysfunction. 4) Long-term maintenance of sinus rhythm may be achieved in up to 50% to 60% of patients by using antiarrhythmic drugs, including sotalol, amiodarone, dofetilide, propafenone, and flecainide, but with the potential for causing significant proarrhythmia and side effects. Radiofrequency catheter ablation may cure over 90% of patients with type 1 AFl (using the tricuspid valve to inferior vena cava isthmus), and from 70% to 90% of patients with atypical AFl. Newer mapping techniques, such as electroanatomic mapping, are likely to further reduce procedure time and improve success rates. |
3,849 | Atrial Fibrillation. | The conversion of atrial fibrillation (AF) to normal sinus rhythm should be attempted in patients who present with this condition, as long as the cure is not worse than the disease itself. In young patients with normal hearts, AF has a small impact on morbidity and mortality. The primary indication for conversion in this population is often symptoms. In contrast, in patients with diseased hearts or who are older than 65 years, maintaining sinus rhythm may have a favorable impact on stroke risk, ventricular function, and symptoms. In the absence of normal sinus rhythm, these patients should receive anticoagulants. Rate control is the preferred first-line strategy for asymptomatic patients and patients presenting with a history of long-standing, persistent AF, making conversion and maintenance of sinus rhythm unlikely. Rate control may be used in patients who develop AF during an acute systemic illness, which will likely terminate with time or therapy. Conversion to sinus rhythm should be considered in patients with a first episode of AF, as unconverted AF tends to perpetuate itself. Conversion can be attempted if the duration of AF is less than 48 hours or if the patient has received anticoagulants when the duration is not known. Other indications for cardioversion are prolonged episodes in patients with otherwise infrequent episodes of paroxysmal AF, and in patients who refuse to take anticoagulants or in whom anticoagulation is contraindicated. After the patient is converted to sinus rhythm, the decision to initiate chronic drug therapy should be based on the presence of other cardiac and medical diseases that increase the risk of recurrence and serious symptoms in case of recurrence (such as hypertrophic cardiomyopathy or mitral stenosis). It is acceptable to manage patients with new-onset AF and normal cardiac function with cardioversion alone and not initiate chronic antiarrhythmic therapy afterwards. However, in patients with abnormal hearts (coronary artery disease, hypertensive or mitral valvular heart disease, and cardiomyopathy) AF is likely to recur, and such patients should be placed on antiarrhythmic medication. |
3,850 | Ibutilide: efficacy and safety in atrial fibrillation and atrial flutter in a general cardiology practice. | Published experience with ibutilide (IB) in randomized clinical trials reveals that conversion to sinus rhythm (SR) occurs in 31% of patients with atrial fibrillation (AF) and in 63% of patients with atrial flutter.</AbstractText>The study was undertaken to test the efficacy and safety of IB in patients with AF and with atrial flutter and to compare them with those reported in previous studies.</AbstractText>In a general cardiology practice, 54 consecutive patients with AF or atrial flutter, no contraindication to IB, and a normal QTc interval, were treated with intravenous IB (0.4-2.0 mg). Duration of arrhythmia, left atrial (LA) size, ejection fraction (EF), time to conversion, QTc interval, and adverse drug events were determined. Patients were observed for a minimum of 6 h. Successful cardioversion was defined as arrhythmia termination within 6 h.</AbstractText>Twenty-four of 34 (70.6%) patients with AF and 15 of 20 (75%) patients with atrial flutter converted to SR. Conversion of AF to SR was more likely to occur if duration of AF was approximately 96 h compared with > 96 h (81 vs. 17%, respectively; p = 0.006). The mean time to arrhythmia termination was 68.8 min. Left atrial size, determined by echocardiogram, was 44 +/- 13 mm in 43 patients. Patients with LA size approximately 45 mm had a conversion rate of 55% in both AF and flutter, compared with a conversion rate of 72% in patients with LA size < 45 mm. Ejection fraction was not a predictor of drug success. The QTc intervals were significantly prolonged after IB administration, with a mean change of 47.1 ms for successfully treated patients. Sustained polymorphic ventricular tachycardia occurred in one patient within 1 min of IB infusion, requiring electrical cardioversion to SR. This patient's serum electrolytes and QTc interval were normal prior to IB infusion; however, the QTc increased by 160 ms (from 387 to 547 ms) during drug infusion. No systemic or pulmonary emboli occurred.</AbstractText>The efficacy of IB for conversion of AF to SR in this prospective observational study was considerably better than previously reported. Duration of AF remains an important predictor of conversion to SR. Complications are rare and without long-term adverse effects.</AbstractText> |
3,851 | Torsades de pointes associated with chlorpromazine: case report and review of associated ventricular arrhythmias. | To present a case of chlorpromazine-associated torsades de pointes, review established cases of ventricular arrhythmias associated with chlorpromazine, and describe the proarrhythmic characteristics of this drug.</AbstractText>Articles identified through a search of MEDLINE and IDIS from January 1966-November 2000 and thorough review of the article bibliographies. Patient cases also were identified from a search of the Food and Drug Administration's Adverse Event Reporting System database (November 1997-March 2001). Cases involving intentional overdoses of chlorpromazine were excluded.</AbstractText>In addition to the case reported herein, 12 cases of documented, chlorpromazine-associated ventricular arrhythmias were identified; five had characteristic features of torsades de pointes. Chlorpromazine delayed repolarization and produced electrocardiographic abnormalities; although, whether chlorpromazine induced torsades de pointes through a mechanism of early afterdepolarizations is unclear. Similar to other instances of drug-induced torsades de pointes, concurrent factors such as electrolyte deficiencies may place the patient at increased risk for arrhythmia.</AbstractText>Chlorpromazine can delay repolarization and produce electrocardiographic abnormalities. These can result infrequently in ventricular arrhythmias and torsades de pointes, particularly in patients with confounding factors.</AbstractText> |
3,852 | Stroke after coronary artery bypass: incidence, predictors, and clinical outcome. | Early postoperative stroke is a serious adverse event after coronary artery bypass grafting (CABG). This study sought to investigate risk factors, prevalence, and prognostic implications of postoperative stroke in patients undergoing CABG.</AbstractText>We investigated the predictors of postoperative stroke (n=333, 2%) in 16 528 consecutive patients who underwent CABG between September 1989 and June 1999 in our institution. Predictors of postoperative stroke were identified by logistic regression analysis.</AbstractText>Among the preoperative and postoperative factors, significant correlates of stroke included (1) chronic renal insufficiency (P<0.001), (2) recent myocardial infarction (P=0.01), (3) previous cerebrovascular accident (P<0.001), (4) carotid artery disease (P<0.001), (5) hypertension (P<0.001), (6) diabetes (P=0.001), (7) age >75 years (P=0.008), (8) moderate/severe left ventricular dysfunction (P=0.01), (9) low cardiac output syndrome (P<0.001), and (10) atrial fibrillation (P<0.001). Postoperative stroke was associated with longer postoperative stay (11+/-4 versus 7+/-3 days for patients without stroke, P<0.001) and with higher in-hospital mortality (14% versus 2.7% for patients without stroke; P<0.001).</AbstractText>Stroke after CABG is associated with high short-term morbidity and mortality. Increased stroke risk can be predicted by preoperative and postoperative clinical factors.</AbstractText> |
3,853 | Prospective evaluation of adenosine-induced proarrhythmia in the emergency room. | The arrhythmogenic hazard of adenosine treatment in an emergency room (ER) has not been established. Thus, in this study, we set out to prospectively determine the prevalence and clinical consequences of the arrhythmogenic effects associated with urgent adenosine treatment in the ER. One hundred and sixty consecutive patients treated with adenosine for regular wide or narrow complex tachyarrhythmias at our ER were included in the study. An initial bolus of 3 mg of adenosine was used, up to a maximum dose of 18 mg (mode 6 mg). Proarrhythmia was defined as the new appearance of any brady- or tachyarrhythmia within 1 minute from the bolus administration of adenosine. Of the 160 study patients, 84% had narrow complex tachycardia and 16% had wide complex tachycardia. Adenosine was effective in the diagnosis and/or treatment of the underlying arrhythmia in 92%. The overall prevalence of adenosine-induced proarrhythmia was 13%, including prolonged AV block inducing asystole > 4 seconds (7%), paroxysmal atrial fibrillation (1%) and non-sustained ventricular tachycardia (5%). All adenosine-induced arrhythmias were transient and subsided spontaneously. It is concluded, firstly, that adenosine-induced proarrhythmia proved to be frequent in a consecutive ER series, and included potentially dangerous arrhythmias. Secondly, nevertheless, all adenosine-induced arrhythmias subsided spontaneously and did not require treatment. Therefore, urgent adenosine treatment is safe and can be recommended in an emergency setting, provided a strict protocol of administration under close monitoring by highly trained personnel. |
3,854 | Ventricular fibrillation following inhalation of Glade Air Freshener. | Intentional hydrocarbon inhalation can be fatal. Death can be secondary to hydrocarbon's cardiopulmonary effects. We present a case of a patient who survived ventricular fibrillation after inhalation of Glade Air Freshener, which contains short chain aliphatic hydrocarbons (butane and isobutane). Unlike our case, myocardial sensitization and hypoxia are more commonly described with aromatic, halogenated or longer chain hydrocarbons. |
3,855 | Conversion of atrial fibrillation into a sinus rhythm by coronary angioplasty in a patient with acute myocardial infarction. | Atrial tachyarrhythmias are important complications occurring in more than 8% of acute myocardial infarctions (AMI). Atrial fibrillation (AFi) during the early phase of AMI is caused by atrial ischaemia, atrial distension due to the left ventricular failure or significant diastolic left ventricular dysfunction. AFi in patients with inferior and posterior AMI indicates at least two vessel coronary diseases, a circumflex coronary artery (CX) occlusion before taking off of the left atrial branches as well as significant stenosis or occlusion of the right coronary artery (RCA). In this article the case of a 67-year-old woman with an acute infero-posterior AMI is described. AMI was complicated with a left heart failure, acute AFi with tachyarrhythmia, transient arterial hypotension and ischaemic mitral regurgitation. Emergency coronary angiography disclosed occlusion of the CX, myocardial infarct related artery, and significant stenoses of the RCA. After opening the occluded CX during the PTCA, AFi with a tachyarrhythmia of 160 beats per minute (bpm) immediately converted into a sinus rhythm with 80 bpm, followed by a normalization of blood pressure and cardiac recompensation. Our case report supports the opinion that AFi in patients with inferior and posterior AMI indicates at least a two-vessel coronary disease. Reopening of the occluded atrial coronary branches during urgent medical treatment was casual and effective treatment of both ischaemic heart disease and consequent AFi. |
3,856 | Arginine vasopressin during cardiopulmonary resuscitation and vasodilatory shock: current experience and future perspectives. | Epinephrine use during cardiopulmonary resuscitation (CPR) is controversial because of its receptor-mediated adverse effects such as increased myocardial oxygen consumption, ventricular arrhythmias, ventilation-perfusion defect, postresuscitation myocardial dysfunction, ventricular arrhythmias, and cardiac failure. In the CPR laboratory, vasopressin improved vital organ blood flow, cerebral oxygen delivery, resuscitability, and neurologic recovery more than did epinephrine. In patients with out-of-hospital ventricular fibrillation, a larger proportion of patients treated with vasopressin survived 24 hours than did patients treated with epinephrine. Currently, a large trial of out-of-hospital cardiac arrest patients being treated with vasopressin versus epinephrine is ongoing in Germany, Austria, and Switzerland. The new international CPR guidelines recommend 40 U vasopressin intravenously, and 1 mg epinephrine intravenously, as equally effective for the treatment of adult patients in ventricular fibrillation; however, no recommendation for vasopressin has been made to date for adult patients with asystole and pulseless electrical activity, or in children, because of lack of clinical data. When adrenergic vasopressors were unable to maintain arterial blood pressure in patients with vasodilatory shock, continuous infusions of vasopressin (0.04-0.10 U/min) stabilized cardiocirculatory parameters and even ensured weaning from catecholamines. |
3,857 | Algorithms to analyze ventricular fibrillation signals. | Prediction of the success of defibrillation to avoid myocardial injury and performance feedback during CPR requires algorithms to analyze ventricular fibrillation signals. This report reviews investigations on different parameters of ventricular fibrillation electrocardiographic signals, including amplitude, frequency, bispectral analysis, amplitude spectrum area, wavelets, nonlinear dynamics, N(alpha) histograms, and combinations of several of these parameters. To date, no satisfactory methods have been found that cope with CPR artifacts and show adequate predictive power of successful defibrillation. The usual limitations of the studies are the small number of subjects, which precludes separation into training and test data. Because many investigations are animal studies of untreated short ventricular fibrillation, the results may be different for prolonged ventricular fibrillation in humans. The universality of threshold values has to be examined, and promising new parameters have to be monitored over longer time periods and analyzed for the effects of chest compressions, ventilation, and concomitant vasopressor therapy. |
3,858 | Technologic advances and program initiatives in public access defibrillation using automated external defibrillators. | Widespread provision of early defibrillation following cardiac arrest holds major promise for improved survival from ventricular fibrillation. The critical element in predicting a successful outcome is the rapidity with which defibrillation is achieved. A worldwide awareness of this potential and its advocacy by such organizations as the American Heart Association have been pivotal in the evolution of initiatives to make defibrillation more widely and more rapidly available. The feasibility of this initiative, known as public access defibrillation, is in large measure a direct consequence of major technologic advances in automated external defibrillators (AEDs). New low-energy waveforms with biphasic morphology have been shown to be more effective in terminating ventricular fibrillation and may do so with less myocardial injury. Placement of AEDs in a variety of nontraditional settings such as police cars, aircraft and airport terminals, and gambling casinos has been shown to yield an impressive number of survivors of cardiac arrest in ventricular fibrillation. Questions yet to be answered center on the appropriate disposition of AEDs in public access defibrillation settings, training and retraining issues, device maintenance, and collection of accurate data to document benefit and to identify areas of needed improvement or expansion of AED availability. |
3,859 | Apical hypertrophic cardiomyopathy (apical hypertrophy): an overview. | Clinical and laboratory data of apical hypertrophy were reviewed based on our experience of over 200 consecutive patients, of whom 126 patients were followed up by myself for more than 1 year (1 to 29 years). Emphasis was placed on various aspects of electrocardiography including the natural course and "wax and wane" phenomenon of giant negative T waves (GNT). Recent diagnostic modality, i.e., cardiac magnetic resonance imaging was also stressed. Apical hypertrophic cardiomyopathy (apical hypertrophy) was mainly discovered by annual health check including electrocardiography and characterized by giant negative T waves (GNT; -1.0-(-)4.2 mV) in the left precordial leads (V4 or V5) in middle-aged men. Transition from normal T wave to negative T wave required several years and remained usually unchanged thereafter. This change may occur rather abruptly on rare occasions. Disappearance of GNT may also occur slowly and progressively in patients, in whom apical aneurysm had developed. The diagnosis may be obtained with echocardiography, left ventriculography or ultrafast computed tomography, but was most accurate with cardiac magnetic resonance imaging, by which identification of the diversity of hypertrophy was achieved, because the multiple short-axis views were accurately obtained in addition to the exact long-axis view. Hypertrophy was not simple but quite complex in both morphology and grade. Gene abnormality may be present even in cases of apical hypertrophy. The prognosis of apical hypertrophy in Japan has been benign, and heart failure due to atrial fibrillation and left ventricular aneurysm due to the destruction of hypertrophied muscle are thought to have prognostic importance, but these were rare in our series. |
3,860 | Natural history of hypertrophic cardiomyopathy: Japanese experience. | Most patients with hypertrophic cardiomyopathy (HCM) remain clinically stable for long periods of time, whereas some patients progress to severe systolic dysfunction. Therefore, the natural history of HCM is largely unknown.</AbstractText>The present study followed up 59 patients with HCM (32 males, 27 females, mean age 38.6 +/- 13.6 years) for 10 years or more (mean 16.0 +/- 4.7 years) after the initial diagnosis.</AbstractText>Eight of 17 patients who showed abnormal Q-waves at the initial examination had lost Q-waves, suggesting remodeling from asymmetric to generalized hypertrophy. The thickness of the interventricular septum showed remarkable changes, increasing by > or = 5 mm in 7 patients and decreasing by > or = 5 mm in 21. These observations indicate that ventricular remodeling occurs in patients with HCM. Follow-up electrocardiography demonstrated new Q-waves in 10 patients and bundle branch blocks or intraventricular conduction disturbances in 13. Left ventricular end-diastolic diameter increased from 41.6 to 48.1 mm, associated with a decrease in fractional shortening from 40.6% to 34.0%. Left ventricular systolic dysfunction, defined as left ventricular end-diastolic diameter > 55 mm or fractional shortening < 25%, developed in 13 patients. These observations indicate that myocardial disease including the conduction system is progressive in patients with HCM and finally deteriorates to systolic dysfunction. Left ventricular outflow obstruction also presented evolutional changes. At the initial study, 23 patients showed systolic anterior motion of the mitral valves. Systolic anterior motion disappeared in 13 patients, reduced in 2, increased in 2, and remained stable in only 6. One patient without systolic anterior motion at the initial study developed new systolic anterior motion. Impaired left ventricular filling increased left atrial diameter from 35.5 to 46.9 mm and atrial fibrillation frequently developed (24 patients).</AbstractText>These findings suggest that HCM is a slowly progressive disease which develops evolutional remodeling of left ventricular hypertrophy and outflow obstruction, eventually progressing to systolic dysfunction with cavity dilation and wall thinning.</AbstractText> |
3,861 | Quantification of left atrial appendage spontaneous echo contrast in patients with chronic nonalvular atrial fibrillation. | The left atrial (LA) appendage is the most common site of thrombus formation in patients with atrial fibrillation, and integrated backscatter allows the quantiative assessment of LA spontaneous echo contrast (SEC). Integrated backscatter was used to examine the significance of measuring appendage SEC, specifically in relation to echocardiographic variables implying thromboembolism, in patients with chronic nonvalvular atrial fibrillation.</AbstractText>Fifty-two patients with chronic nonvalvular atrial fibrillation and no prior anticoagulant therapy (35 men, 17 women, mean age 66 +/- 7 years) underwent transesophageal echocardiography with integrated backscatter analysis. The LA and LA appendage integrated backscatter intensity were measured with the regions of interest placed in the LA cavity and the appendage, respectively. The integrated backscatter intensity values for these two chambers (corrected "LA" and "LA appendage" integrated backscatter intensity, respectively) were corrected using values from the left ventricular cavity.</AbstractText>The LA appendage integrated backscatter intensity values were available in 44 patients (85%). Overall, the corrected LA appendage integrated backscatter intensity was significantly increased compared with the corrected LA integrated backscatter intensity (2.8 +/- 2.2 vs 2.0 +/- 1.8 dB, p < 0.001). The corrected LA appendage integrated backscatter intensity was inversely correlated with the LA appendage velocity (r = -0.37, p < 0.05), but not with the LA dimension, appendage size, or left ventricular function. The corrected appendage integrated backscatter intensity (4.5 +/- 2.3 vs 2.4 +/- 1.9 dB, p < 0.01) and LA integrated backscatter intensity (3.2 +/- 2.1 vs 1.7 +/- 1.7 dB, p < 0.05) were higher in patients who had LA appendage thrombus (n = 8) than those who did not. With the corrected appendage integrated backscatter intensity set at > or = 2.5 dB, the sensitivity for the presence of appendage thrombus was 88% and the specificity was 64%.</AbstractText>Patients with chronic nonvalvular atrial fibrillation had a denser SEC in the LA appendage compared with SEC in the main LA cavity. The severity of the appendage SEC was influenced by the LA appendage function rather than its size. Quantification of SEC in the appendage, rather than main LA cavity, was more valuable for assessing embolic potential.</AbstractText> |
3,862 | Connective tissue skeleton in the normal left ventricle and in hypertensive left ventricular hypertrophy and chronic chagasic myocarditis. | Pictures certainly are worth a thousand words in the case of the structure of the connective tissue skeleton of normal and diseased myocardium. This report reviews the connective tissue matrix of the normal human myocardial tissue and the pathological myocardial fibrosis in left ventricular hypertrophy due to chronic arterial hypertension in humans and in human chronic chagasic myocarditis. The myocardial connective tissue matrix was studied employing a cell-maceration method that removes the myocardial tissue non-fibrous elements, and leaves behind a non-collapsed matrix, thus allowing a better three-dimensional view. Such information extends our knowledge of the expression of interstitial myocardial fibrous tissue in normal hearts and in hypertensive left ventricular hypertrophy and chronic chagasic myocarditis. The progressive accumulation of interstitial collagen fibers in both chronic cardiac diseases may be expected to decrease myocardial compliance and disrupt synchronous contractions of the ventricles during systole, contributing to a spectrum of ventricular dysfunction that involve either the diastolic or systolic phase of the cardiac cycle or both. In hypertensive heart disease myocardial fibrosis can be also implicated in the genesis of ventricular dysrhythmias, possible causes of sudden death among chronic hypertensive patients. Regarding chronic chagasic myocarditis, myocardial fibrosis is probably implicated in the genesis of malignant ventricular tachyarrhythmias (ventricular tachycardia and ventricular fibrillation), major causes of sudden death among patients with chronic Chagas' heart disease. The collagen distribution could interfere on the electrical properties of the myocardium. Fibrosis can block the cardiac impulse that may recycle (re-entry) through an alternative route and could slow conduction. In addition, the thick collagenous septa encompassing muscle fiber bundles could interfere with lateral impulse conduction, which would favor re-entry. Moreover, the methodology used is a useful tool to study the spatial organization of the collagen fibrils of the myocardium under normal and pathological conditions. |
3,863 | Heart failure: update on treatment and prognosis. | HF is a prevalent and debilitating disease, affecting nearly 5 million patients and perhaps an equal number with asymptomatic left ventricular dysfunction who are at high risk of atrial fibrillation developing. An estimated 550,000 new cases occur every year. HF is the most common diagnosis in hospitalized patients aged 65 and over and is a major cause of death. The median survival after onset is 1.7 years in men and 3.2 years in women. The majority of cardiac deaths in patients with HF are sudden and arrhythmogenic: the rest are due to progressive hemodynamic deterioration. A significant advance in the past decade has been the recognition of the importance of inhibiting the neurohormonal action in HF with the use of beta-blockers, angiotensin receptor, and aldosterone antagonists. In addition, a new concept in HF therapy has evolved. The view that chronic HF is an irreversible, end-stage process is being supplanted by the fact that it is possible to effect biological improvement in the intrinsic defects of function and structure in hearts afflicted with chronic HF. Reversibility of HF has been reported by (1) unloading the failing heart using an LVAD, (2) the sophisticated use of diuretic combinations and neurohormonal blocking drugs, or (3) employing continuous arteriovenous hemofiltration. Thus it is now possible to reverse a process that has long been considered irreversible. Exercise programs designed for patients with HF that have been advocated recently can be difficult to apply. Fine tuning of an exercise regimen is required because a reduction in cardiac work is mandatory when treating HF, where the concern is that the heart may not be capable of supplying the metabolic needs of the body, even in resting states. Finally, although not emphasized in the recent literature on HF, the use of diuretics and sodium restriction continue to be the mainstays of therapy without which compensation of HF is not possible. |
3,864 | Colorectal patients and cardiac arrhythmias detected on the surgical high dependency unit. | Surgical high dependency unit (SHDU) care is becoming an integral feature of colorectal surgical practice. Routine ECG monitoring is a feature of surgical care in this setting. The aim of this study was to determine the incidence and outcome of cardiac arrhythmias detected in an SHDU population of colorectal patients.</AbstractText>226 patients over a 12 month period were admitted to a 6-bedded SHDU under the care of 3 colorectal surgeons. A total of 29 patients (13%) had significant arrhythmias on ECG monitoring (median age 74 years, range 35-88 years). Pre-existing ischaemic heart disease was present in 9 patients--colorectal cancer and inflammatory bowel disease accounted for the underlying problem in the majority of these patients.</AbstractText>Equal numbers of supraventricular and ventricular arrhythmias were detected--atrial fibrillation being the most commonly detected abnormality. Therapeutic intervention (electrolyte correction and anti-arrhythmic agents) was required in 23 patients. One patient required DC shock for ventricular fibrillation. Seven patients were transferred to the heart care unit or intensive care unit to manage their cardiac problems. Two patients died as a result of their cardiac problem, 27 were discharged home alive--3 on long-term anti-arrhythmic therapy.</AbstractText>The postoperative environment of colorectal patients has been radically altered by the introduction of the SHDU. If colorectal surgeons are to remain central to the postoperative care of their patients, all surgical staff will require training in the recognition and protocol prevention and management of cardiac arrhythmias. Certification of colorectal surgeons in advanced life support is more relevant to colorectal surgery than certification in trauma care.</AbstractText> |
3,865 | Baseline factors predicting early resumption of driving after life-threatening arrhythmias in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. | In the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial, patients with ventricular fibrillation or hemodynamically unstable ventricular tachycardia were randomly assigned to receive either an implantable cardioverter-defibrillator (ICD) or antiarrhythmic drug therapy. As part of the trial, patients were asked to participate in a prospective driving survey. The purpose of the survey was to determine what baseline factors and patient characteristics specifically predicted resumption of driving earlier than advised by current guidelines.</AbstractText>Patients were surveyed anonymously as to their driving habits in the initial period after random assignment and every 6 months thereafter. AVID study coordinators were independently asked to assess their patients' driving status as well. The relation between baseline factors and time to resumption of driving was explored by means of Kaplan-Meier estimates for univariate analyses and the stepwise Cox proportional hazards regression model for multivariate analyses.</AbstractText>There were 802 patients who were eligible for assessment of driving status. The majority of patients (58%) resumed driving an automobile within 6 months of their index arrhythmia regardless of whether they received drug therapy or an ICD. By multivariate analysis, patients who were younger than 65 years of age, male, and college educated were more likely to drive early, as were patients whose index arrhythmia was ventricular tachycardia.</AbstractText>Younger, college-educated men and those whose index arrhythmia is ventricular tachycardia are most likely to resume driving <6 months after the initiation of therapy for a potentially life-threatening ventricular arrhythmia. Patients with an ICD did not appear to resume driving later than those who were discharged on antiarrhythmic drugs alone.</AbstractText> |
3,866 | Incidence and short-term prognosis of late sustained ventricular tachycardia after myocardial infarction: results of the Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI-3) Data Base. | There is little epidemiologic information from large multicenter databases on sustained monomorphic ventricular tachycardia occurring after the initial 48 hours of myocardial infarction.</AbstractText>We reassessed its incidence and short-term prognosis in 16,842 patients with a definite myocardial infarction enrolled in the Gruppo Italiano per lo Studio della Soprovvivenza nell'Infarto Miocardico (GISSI-3) trial.</AbstractText>The incidence rate of late sustained ventricular tachycardia by 6 weeks was around 1%. Older age, a history of hypertension, diabetes, and myocardial infarction, nonadministration of lytic therapy, Killip class > I, > or = 6 leads with ST-segment elevation, higher heart rate, and bundle branch block on admission were significantly more frequent among patients with than without late sustained ventricular tachycardia. Patients with ventricular tachycardia had a more complicated course in-hospital and posthospital to 6 weeks than the reference group did. The arrhythmia was associated with a significant excess of pump failure, atrial flutter-fibrillation, asystole, atrioventricular block, ventricular fibrillation within the first 48 hours of myocardial infarction, and recurrent ischemic events. Larger left ventricular end-systolic volumes and lower ejection fractions were more frequent among ventricular tachycardia patients than in the reference group by 6 weeks. Death rates by 6 weeks were 35% for patients with ventricular tachycardia and 5% for those without the arrhythmia. Irrespective of the stratification of patients by site and type of infarct and presence/absence of bundle branch block, the occurrence of the arrhythmia was associated with reduced 6-week survival.</AbstractText>In a proportional hazard regression model late sustained ventricular tachycardia was retained as a strong, independent predictor of 6-week mortality after myocardial infarction (hazard ratio 6.13, 95% confidence interval 4.56-8.25).</AbstractText> |
3,867 | Magnolol reduces myocardial ischemia/reperfusion injury via neutrophil inhibition in rats. | The accumulation of oxygen-free radicals and activation of neutrophils are strongly implicated as important pathophysiological mechanisms mediating myocardial ischemia/reperfusion injury. It has been proven that various antioxidants have cardioprotective effects. Magnolol, an active component extracted from the Chinese medicinal herb Magnolia officinalis, possesses potent antioxidant and free radical scavenging activities. In this study, the cardioprotective activity of magnolol was evaluated in an open-chest anesthetized rat model of myocardial ischemia/reperfusion injury. The results demonstrated that pretreatment with magnolol (0.2 and 0.5 microg/kg, i.v. bolus) at 10 min before 45 min of left coronary artery occlusion, significantly suppressed the incidence of ventricular fibrillation and mortality when compared with the control group. Magnolol (0.2 and 0.5 microg/kg) also significantly reduced the total duration of ventricular tachycardia and ventricular fibrillation. After 1 h of reperfusion, pretreatment with magnolol (0.2 and 0.5 microg/kg) caused a significant reduction in infarct size. In addition, magnolol (0.2 microg/kg) significantly reduced superoxide anion production and myeloperoxidase activity, an index of neutrophil infiltration in the ischemic myocardium. In addition, pretreatment with magnolol (0.2 and 0.5 microg/kg) suppressed ventricular arrhythmias elicited by reperfusion following 5 min of ischemia. In vitro studies of magnolol (5, 20 and 50 microM) significantly suppressed N-formylmethionyl-leucyl-phenylalanine (fMLP; 25 nM)-activated human neutrophil migration in a concentration-dependent manner. It is concluded that magnolol suppresses ischemia- and reperfusion-induced ventricular arrhythmias and reduces the size of the infarct resulting from ischemia/reperfusion injury. This pronounced cardioprotective activity of magnolol may be mediated by its antioxidant activity and by its capacity for neutrophil inhibition in myocardial ischemia/reperfusion. |
3,868 | Atrial fibrillation after coronary artery bypass graft surgery is unrelated to cardiac abnormalities detected by transesophageal echocardiography. | Atrial fibrillation is a common complication of coronary artery bypass graft (CABG) surgery that is associated with adverse patient outcomes. We evaluated whether preexisting abnormalities of cardiac structure or function detected with transesophageal echocardiography (TEE) are prevalent in patients later developing atrial fibrillation after CABG surgery. TEE imaging was performed after induction of general anesthesia, but before primary CABG surgery, in 62 consecutive patients without cardiac valvular disease or preexisting atrial fibrillation. Measurements included left atrial diameter, left ventricular wall thickness, left ventricular end-systolic and end-diastolic dimensions and fractional area change. Pulsed-wave Doppler measurements of pulmonary venous and trans-mitral blood flow velocity were obtained. Continuous monitoring with telemetry electrocardiography for the development of atrial fibrillation was performed. Eighteen patients (29%) developed postoperative atrial fibrillation. There were no significant differences in left atrial or left ventricular TEE variables or pulsed-wave Doppler pulmonary venous flow measurements between patients with and without postoperative atrial fibrillation. After adjusting for age and duration of aortic cross-clamping, there were no differences in the transmitral Doppler diastolic filling variables between these same groups. These data suggest that atrial fibrillation commonly occurs after CABG surgery in the absence of atrial enlargement or Doppler-derived cardiac functional abnormalities. The data imply that the use of TEE immediately before surgery would be an insensitive means for routine identification of patients susceptible to this arrhythmia.</AbstractText>Transesophageal echocardiography performed immediately before coronary artery bypass graft (CABG) surgery is not useful for prediction of susceptibility to develop atrial fibrillation postoperatively. Postoperative atrial fibrillation commonly occurs after CABG surgery in the absence of preoperative atrial enlargement or Doppler derived functional abnormalities.</AbstractText> |
3,869 | Localized right ventricular morphological abnormalities detected by electron-beam computed tomography represent arrhythmogenic substrates in patients with the Brugada syndrome. | This study was designed to determine, using electron-beam CT, whether there are morphological abnormalities in patients with the Brugada syndrome and to elucidate the relationship between those abnormalities and arrhythmogenesis.</AbstractText>Twenty-six consecutive patients with the Brugada syndrome and 23 age- and gender-matched control subjects (controls) were evaluated for morphological abnormalities using electron beam CT. Electron beam CT demonstrated morphological abnormalities of the right ventricle in 21 (81%) of 26 patients, but in only two (9%) of 23 controls. The sites of morphological abnormalities were the right ventricular outflow tract area in 17 patients and the inferior wall of the right ventricle in four patients. Of the seven patients with monoform premature ventricular contractions recorded only in the acute phase, four of the five patients with premature ventricular contractions from the right ventricular outflow tract area had morphological abnormalities in the right ventricular outflow tract area, and the other two patients with premature ventricular contractions from the inferior wall of the right ventricle had morphological abnormalities in the inferior wall of the right ventricle.</AbstractText>The sites of morphological abnormalities detected by electron beam CT in patients with the Brugada syndrome were related to the origins of premature ventricular contractions recorded only in the acute phase, which may trigger ventricular fibrillation. These morphological abnormalities may be related to arrhythmogenic substrates in patients with the Brugada syndrome.</AbstractText> |
3,870 | Adenosine-induced ventricular fibrillation. | The use of adenosine has been suggested as a diagnostic tool in the evaluation of wide ORS complex tachycardia. However, adenosine shortens the antegrade refractoriness of accessory atrioventricular connections and may cause acceleration of the ventricular rate during atrial fibrillation. We observed ventricular fibrillation in 2 patients who presented to the emergency department with pre-excited atrial fibrillation and were given 12 mg of adenosine. |
3,871 | Valvular heart operation in patients with previous mediastinal radiation therapy. | The outcome of valvular heart operations in patients with previous mediastinal radiation therapy was studied.</AbstractText>This is a single center retrospective study of 60 patients (37 females, 23 males) with a mean age of 62 +/- 15 years (28 to 88 years old) operated on from January 1976 to December 1998. Valvular heart operations performed included aortic valve replacements (n = 26), mitral valve procedures (n = 16), tricuspid valve procedures (n = 6), and multiple valve procedures (n = 12). A total of 264 clinical, hemodynamic, electrocardiographic and echocardiographic variables were analyzed.</AbstractText>Total follow-up was 199 patient-years with a mean of 3.3 +/- 3.1 years and a range of 0 to 12.4 years old. Early mortality was 7 patients (12%). Early mortality in patients with constrictive pericarditis was 40% (4 of 10) compared with 6% (3 of 50) in patients without constrictive pericarditis. By univariate analysis, early mortality was associated with constrictive pericarditis (p = 0.011), reduced preoperative ejection fraction (p = 0.015), and longer cardiopulmonary bypass times (p = 0.037). A total of 14 patients (23%) required permanent pacemaker placement before (n = 7), during (n = 1), or early (n = 6) after valvular heart operations. There were 19 late deaths (malignancies, 7; heart failures, 5; other cardiac, 4; and other noncardiac, 3). Overall survival and freedom from late cardiac death and cardiac reoperation at 5 years for hospital survivors were 66% +/- 8%, 82% +/- 7%, and 93% +/- 4%, respectively. By univariate analysis, late cardiac death was associated with low ejection fraction (p = 0.002), New York Heart Association (NYHA) functional class IV (p = 0.004), preoperative congestive heart failure (p = 0.02), and preoperative atrial fibrillation (p = 0.038). Eighty-five percent of the discharged patients were in NYHA functional class I or II at follow-up.</AbstractText>Early results of valve replacement after mediastinal radiation therapy were good except in the presence of constrictive pericarditis. Long-term outcome was limited by malignancy and heart failure. Early surgical intervention is recommended before the development of risk factors for late death, namely, severe symptoms, left ventricular dysfunction, and atrial fibrillation.</AbstractText> |
3,872 | An exceptional case of complete neurologic recovery after more than 5-h cardiac arrest. | We describe a case of more than 5 h cardiac arrest in a 60-year-old patient who underwent general anesthesia for a urologic operation. Before extubation, the patient suddenly developed ventricular fibrillation, pulseless ventricular tachycardia and asystole which was immediately treated by advanced life support (ALS) measures. Thirty minutes later seizures developed and were controlled by 200 mg of thiopentone and 10 mg of diazepam. A pattern of ventricular tachycardia, coarse ventricular fibrillation and asystole lasted for nearly 120 min. Termination of resuscitation maneuvers was considered, but long-term life support was continued for 5 h. After this time, peripheral pulses, with a supraventricular tachycardia-like rhythm and regular spontaneous breathing reappeared. Seven hours later, the patient had a Glasgow Coma Scale (GCS) of 5, dilated unresponsive, absence of pupils, and a systolic arterial pressure of 100 mmHg. He was then transferred to intensive care unit (ICU). The morning after, the patient was awake, responded to simple orders, breathing spontaneously, and free from sensomotor deficit. He was, therefore, extubated. Subsequently, other episodes of transitory ST-line upper wave followed by ventricular fibrillation appeared, suggesting Prinzmetal angina. This was successfully treated by percutaneous coronary angioplasty. The first electroencephalogram recorded the day after cardiac arrest showed a mild widespread background slowing. An electroencephalogram 6 days later showed a return to alpha rhythm with only mild theta-wave abnormalities. Four weeks after the first cardiac arrest the patient was discharged. This is an exceptional experience compared with the others reported. We believe that all the efforts must not be given up when such an event occurs during anesthesia and there are optimal conditions for resuscitation maneuvers. |
3,873 | Long-term mild hypothermia with extracorporeal lung and heart assist improves survival from prolonged cardiac arrest in dogs. | although normothermic extracorporeal lung and heart assist (ECLHA) improves cardiac outcomes, patients can not benefit from hypothermia-mediated brain protection. The present study evaluated the effects of long-term ECLHA with mild to moderate hypothermia (33 degrees C) in a canine model of prolonged cardiac arrest.</AbstractText>15 dogs were assigned to either the hypothermic (seven dogs, 33 degrees C) or normothermic group (eight dogs, 37.5 degrees C). All dogs were induced to normothermic ventricular fibrillation (VF) for 15 min, followed by 24 h of ECLHA and 72 h of intensive care. The hypothermia group maintained core (pulmonary artery) temperature at 33 degrees C for 20 h starting from resuscitation, then were rewarmed by 28 h. Outcome evaluations included: (1) mortality; (2) catecholamine dose; (3) time to extubation; (4) necrotic myocardial mass (g); and (5) neurological deficits score (NDS).</AbstractText>in the normothermic group five dogs died of cardiogenic shock and one dog succumbed to poor oxygenation. The two surviving dogs remained comatose (NDS 60.5 +/- 4.9%) with necrotic myocardial mass of 14.5 +/- 3.5 g. In the hypothermic group, one dog died from pulmonary dysfunction, the other six dogs survived. The surviving dogs showed brain damage (29.8 +/- 2.5%), but there was evidence of some brain-protective effect. The mass of necrotic myocardium was 4.2 +/- 1.3 g in the hypothermic group or 3.4 times smaller than in the normothermic group. The survival rate was significantly higher in the hypothermic than in the normothermic group (P < 0.05). The catecholamine requirement was also lower in the hypothermic than in the normothermic dogs (P < 0.05).</AbstractText>Long-term mild to moderate hypothermia with ECLHA induced immediately after cardiac arrest improved survival as well as cerebral and cardiac outcomes.</AbstractText> |
3,874 | Geographical distribution of cardiac arrest in Nottinghamshire. | to analyse the incidence of out-of-hospital cardiac arrest in Nottinghamshire; to ascertain its geographical distribution; and to determine whether the geography of coronary heart disease mortality and out-of-hospital cardiac arrest are the same.</AbstractText>population based, retrospective study in the County of Nottinghamshire with a total population of 993,914 in an area of 2183 km2 divided into 191 electoral areas. In the 4 years from 1 January, 1991 to 31 December, 1994, 1634 patients sustained a cardiac arrest attributed to a cardiac cause (International Classification of Diseases codes 390-414 and 420-429) and were attended by the Nottinghamshire Ambulance Service. The overall crude mean incidence rate of community cardiac arrest per electoral area was 40.2 per 100,000 population (range 0-121.2). Thirteen electoral areas, relatively deprived according to the Townsend score, had a significantly greater than expected incidence rate of cardiac arrest (median of 75.6/100,000 per electoral area; interquartile range (IQR) 65.3, 83.8). Twelve relatively affluent electoral areas had a significantly lower than expected incidence rate (median of 18.5/100,000 per area (IQR 13.0, 28.7). After adjusting for deprivation index, there were no differences in coronary heart disease (CHD) mortality and community cardiac arrest in urban and rural electoral areas. Apart from response times by ambulance crews, the events that follow the cardiac arrest such as bystander resuscitation, ventricular fibrillation found as the presenting rhythm and survival were similar in all electoral areas.</AbstractText>increasing level of deprivation is associated with areas of increased incidence of out-of-hospital cardiac arrest in Nottinghamshire, and the effect is apparently different from that on CHD mortality. There is scope for reducing incidence rates of community cardiac arrest and to introduce strategies to improve survival in areas identified as having high rates of community cardiac arrest.</AbstractText> |
3,875 | Characteristics and outcome among patients suffering in-hospital cardiac arrest in monitored and non-monitored areas. | To describe the characteristics and outcome among patients suffering in-hospital cardiac arrest in relation to whether the arrest took place in a ward with monitoring facilities.</AbstractText>All patients who suffered an in-hospital cardiac arrest during a 4-year period in Sahlgrenska Hospital, Göteborg, Sweden and in whom resuscitative efforts were attempted, were prospectively recorded and described in terms of characteristics and outcome.</AbstractText>Among 557 patients, 292 (53%) had a cardiac arrest in wards with monitoring facilities. Those in a monitored location more frequently had a confirmed or possible acute myocardial infarction (AMI) as judged to be the cause of arrest (P < 0.0001), and the arrest was witnessed more frequently (96 vs. 79%; P < 0.0001). Ventricular fibrillation/tachycardia was observed more often as initial arrhythmia in monitored wards (56 vs. 44%; P = 0.006). The median interval between collapse and first defibrillation was 1 min in monitored wards and 5 min in non-monitored wards (P < 0.0001). Among patients with arrest in monitored wards 43.2% were discharged alive compared with 31.1% of patients in non-monitored wards (P = 0.004). Cerebral performance category (CPC-score) at discharge was somewhat better among survivors in monitored wards.</AbstractText>In a Swedish University Hospital 47% of in-hospital cardiac arrests in which resuscitation was attempted took place in wards without monitoring facilities. These patients differed markedly from those having arrest in wards with monitoring facilities in terms of characteristics, interval to defibrillation and outcome. A shortening of the interval between collapse and defibrillation in these patients might increase survival even further.</AbstractText> |
3,876 | Factors associated with the occurrence of cardiac arrest during hospitalization for acute myocardial infarction in the second national registry of myocardial infarction in the US. | Cardiac arrest can occur as a complication of acute myocardial infarction (AMI). To date, few studies have described factors associated with cardiac arrest occurrence and survival during hospitalization for treatment of AMI. We used data from a large national registry of hospitalized AMI patients to identify these factors. Data were collected from 1073 participating institutions, representing 14.4% of US hospitals. Hospital site coordinators conducted periodic chart reviews for AMI patients and data were submitted to an independent center for periodic review. Univariate analysis and multivariate logistic regression were used to identify factors associated with cardiac arrest. We found that cardiac arrest occurred in 4.8% (14,725/305,812) of hospitalized AMI patients. The survival rate to hospital discharge for these individuals was 29.4%. Sustained ventricular tachycardia or fibrillation (VT/VF) was present in 34.7% and was associated with a higher rate of survival to hospital discharge compared to cardiac arrest patients without a ventricular tachyarrhythmia (47.5 vs. 19.8%, P < 0.00001). Hypotension (initial systolic BP < 90 mmHg), q-wave AMI, old age, heart failure and initial heart rate abnormalities (bradycardia or tachycardia) were associated with a higher prevalence of cardiac arrest. A higher percentage of women compared to men experienced cardiac arrest (6.0 vs. 4.41%, P < 0.0001). Cardiac arrest prevalence was lower in patients with inferior wall infarction than in other types of ST-elevation infarction. Use of reperfusion therapy (PTCA or tPA) was associated with improved survival compared to hospitalized AMI patients who did not receive such therapy. |
3,877 | Evaluation of a hospital-wide resuscitation team: does it increase survival for in-hospital cardiopulmonary arrest? | To assess the impact (defined not only with regard to patient outcome but also to record keeping for evaluation of care) of a formal, structured resuscitation team for in-hospital cardiopulmonary resuscitation over the year following its creation.</AbstractText>This is a "before and after" study in which charts of all patients needing resuscitation during the two-year period were reviewed and data arranged in the Utstein Style of in-hospital reporting of cardiac arrests. The review was limited to adults (> or = 18 years of age) in nonICU settings.</AbstractText>A total of 220 events were identified. Demographics and presenting rhythms for the two periods under review were similar. For the period of August 1996-August 1997 (group 1), there were 70 resuscitation events recorded with a return of spontaneous circulation (ROSC) rate of 21/70 (30%). For the period of August 1997-August 1998 (group 2), 150 events were recorded and the ROSC rate was significantly higher 87/150 (58%)) (P=0.0002). ROSC after ventricular fibrillation and ventricular tachycardia was similar in both groups (50 vs 57%) (P = 1.00) but an improvement in survival was seen in group 2 from events of bradycardia perfusing rhythm (25% vs 84%) (P = 0.0003). Survival from PEA/Asystole was also improved during period 2 (18 vs 48%) (P = 0.013). Survival to discharge was seen in 3/50 (6%) of patients in period 1 and 18/102 (18%) of patients in period 2 (P = 0.09).</AbstractText>The formation of a structured, formalized hospital resuscitation team was associated with an increase in the number of recorded events, in the number of patients experiencing ROSC and in the percentage of patients who were discharged from the hospital. Facilities with no formal resuscitation team or with no skilled, practiced resuscitator on their current team should consider implementation of a similar strategy.</AbstractText> |
3,878 | Comparison of the hemodynamic effects of milrinone with dobutamine in patients after cardiac surgery. | To compare the hemodynamic effects, efficacy, and safety of intravenous milrinone (M), 50 microg/kg during 10 minutes followed by 0.5 microg/kg/min, with intravenous dobutamine (D), 10 to 20 microg/kg/min, in patients with low cardiac output after cardiac surgery.</AbstractText>Randomized, open-label, multicenter study.</AbstractText>Cardiothoracic surgery departments, operating rooms, and intensive care units in 6 university hospitals.</AbstractText>Patients (n = 120; 60 per group) after elective cardiac surgery.</AbstractText>None.</AbstractText>Analysis compared the hemodynamics at baseline and the percentage change from baseline during 4 hours of the drug infusion. The incidence of adverse events was recorded. Both groups had low mean (+/- SEM) cardiac indices (M, 1.6 ([0.03] L/min/m(2); D, 1.7 [0.03] L/min/m(2)) in association with adequate mean pulmonary capillary wedge pressures (M, 13.7 [1.3] mmHg; D, 12.7 [1.9] mmHg) at baseline. Group M had significantly higher systemic arterial pressures and systemic vascular resistances compared with group D; otherwise, the hemodynamics in both groups were comparable. During the study, hemodynamic responses included the following: group D had greater increases in cardiac index (at 1 hour, D = 55%, M = 36%; p < 0.01), heart rate (at 1 hour, D = 35%, M = 10%; p < 0.001), arterial pressures (mean arterial pressure at 1 hour, D = 31%, M = 7%; p < 0.001), and left ventricular stroke work index (at 1 hour, D = 75%, M = 45%; p < 0.05). Group M had greater decreases in mean pulmonary capillary wedge pressure (at 1 hour, D = -3%, M = -14%; p < 0.05). Comparisons of adverse events showed that dobutamine was associated with a higher incidence of hypertension (D = 40%, M = 13%; p < 0.02) and change of rhythm from sinus to atrial fibrillation (D = 18%, M = 5%; p < 0.04). Milrinone was associated with a higher incidence of sinus bradycardia (D = 2%, M = 13%; p < 0.03).</AbstractText>Milrinone and dobutamine are appropriate and comparable for the pharmacologic treatment of the low- output syndrome after cardiopulmonary bypass.</AbstractText>Copyright 2001 by W.B. Saunders Company.</CopyrightInformation> |
3,879 | Transesophageal echocardiographic evaluation of native aortic valve area: utility of the double-envelope technique. | To assess the accuracy of aortic valve area (AVA) calculations using the continuity equation with data obtained from the double envelope (DE) (simultaneously obtained left ventricular outflow tract [V1]) and aortic valve [V2] velocities) during intraoperative transesophageal echocardiography (TEE).</AbstractText>Prospective study; measurements were performed on-line.</AbstractText>University hospital.</AbstractText>Cardiac and noncardiac surgical patients (n = 75) with recent aortic valve assessment (<3 months) undergoing general anesthesia or endotracheal intubation.</AbstractText>Intraoperative AVA was measured by the continuity equation using the DE technique (DE/TEE) and by planimetry (PL/TEE). Left ventricular outflow tract diameter was obtained from midesophageal views, whereas subvalvular (V1) and valvular (V2) velocities were obtained simultaneously using continuous-wave Doppler from transgastric views. V1 was also obtained using pulsed-wave Doppler. Measurements were compared with AVA obtained preoperatively by the Gorlin equation during cardiac catheterization (G/CATH) or by transthoracic echocardiography using the traditional continuity equation (C/TTE) (nonsimultaneously obtained V1 and V2).</AbstractText>A DE was obtained in 73 of 75 patients (97%). Four patients had atrial fibrillation at the time of the examination, whereas the rest were in sinus rhythm. PL/TEE was performed in 54 of 71 patients with sinus rhythm (76%). Agreement was good between DE/TEE and G/CATH (mean bias, 0.02 cm(2) [SD, 0.24 cm(2)]), and C/TTE (mean bias, -0.05 cm(2) [SD, 0.16 cm(2)]). Agreement was not as good between PL/TEE and G/CATH (mean bias, -0.07 cm(2) [SD, 0.28 cm(2)]) and C/TTE (mean bias, -0.13 cm(2) [SD, 0.30 cm(2)]). V1 obtained by pulsed-wave Doppler and with DE closely agreed (mean bias, 0.01 m/sec [SD, 0.05 m/sec]).</AbstractText>TEE evaluation of native AVA using the DE technique is feasible and in good agreement with that obtained by C/TTE and G/CATH. Compared with DE/TEE, PL/TEE did not agree as well. Use of DE/TEE should simplify the continuity equation and may minimize errors resulting from beat-to-beat variability in stroke volume.</AbstractText>Copyright 2001 by W.B. Saunders Company.</CopyrightInformation> |
3,880 | Relationship between pacemaker dependency and the effect of pacing mode on cardiovascular outcomes. | A recently completed trial, the Canadian Trial of Physiological Pacing (CTOPP), showed that physiological pacing did not significantly reduce mortality, stroke, or heart failure hospitalization, but it did show that atrial fibrillation occurred less frequently in patients with physiological pacing. Many pacemaker patients experience only transient bradyarrhythmias with an adequate unpaced heart rate (UHR) and are not pacemaker-dependent. The purpose of the present analysis was to determine if pacemaker-dependent patients have an increased benefit from physiological pacing compared with non-pacemaker-dependent patients.</AbstractText>Of 2568 patients included in the CTOPP trial, 2244 patients had a pacemaker dependency test performed at the first follow-up visit. The yearly event rate of cardiovascular death or stroke steadily increased with decreasing UHR in the ventricular pacing group, but it remained constant in the physiological pacing group. When the patients were subdivided to UHR </=60 bpm or >60 bpm, there was an interaction between pacing mode treatment and UHR subgroup. The Kaplan-Meier plot confirmed a physiological pacing advantage only in the UHR </=60 bpm subgroup. This differential effect was also present for the outcomes of cardiovascular death and total mortality.</AbstractText>This study demonstrated that UHR at first follow-up has an important influence on how pacing mode selection affects cardiovascular death and total mortality. Pacemaker-dependent patients with low UHR will probably be paced frequently and will likely benefit from physiological pacing. In contrast, non-pacemaker-dependent patients will likely be paced infrequently and may not benefit from physiological pacing.</AbstractText> |
3,881 | Arrhythmogenesis in isolated rat hearts with enhanced alpha-adrenoceptor-mediated responsiveness. | 1. It has been postulated that stimulation of myocardial alpha-adrenoceptors is one of the primary mediators of the dysrhythmias which occur during periods of myocardial ischaemia and reperfusion. This study examines arrhythmogenesis during coronary artery occlusion and reperfusion in isolated perfused rat hearts from control animals and from rats with enhanced myocardial alpha-adrenoceptor responsiveness. 2. Rats were administered propylthiouracil (PTU) in their drinking water for 8 weeks. This treatment resulted in an enhanced responsiveness of isolated left atria to the alpha-adrenoceptor agonist phenylephrine compared with atria from control animals. 3. In Langendorff-perfused isolated hearts, the spontaneous rate of contraction was significantly lower in the PTU-pretreated group than in either age-matched or weight-matched controls. Occlusion of the left anterior descending artery (LAD) for 25 min resulted in ventricular tachycardia (VT) of similar incidence and duration in all groups and ventricular fibrillation (VF) in both control groups but not the PTU-pretreated group. 4. Following the 25-min ischaemic period the myocardium was reperfused for 10 min. The incidence and duration of VT and VF during this period was similar in all groups except that the duration of VF in the PTU-pretreated group was significantly lower than in controls. 5. In perfused hearts paced at 4 Hz, the incidence and duration of dysrhythmias during ischaemia and reperfusion was again similar in all groups, only the duration of VF being affected (reduced) by PTU-pretreatment. 6. In conclusion, this study does not lend support to the hypothesis that myocardial alpha-adrenoceptors have a primary role in arrhythmogenesis, but the data would support a role for these receptors in myocardial protection. |
3,882 | Mechanical alternans in patients with chronic heart failure. | Clinical implications of mechanical alternans in patients with chronic heart failure have remained uncertain. In this study, prevalence, characteristics, and prognostic implications of mechanical alternans were investigated.</AbstractText>Consecutive 51 patients with dilated cardiomyopathy underwent diagnostic cardiac catheterization using a micromanometer-tipped catheter. Under basal conditions, 7 of 35 patients with sinus rhythm showed mechanical alternans. Physiologic tachycardia (110 bpm) induced mechanical alternans in another 15 patients with sinus rhythm and in another 10 of 16 patients with atrial fibrillation. Low doses of dobutamine also induced mechanical alternans in another 8 patients, but a high dose of dobutamine eliminated mechanical alternans. Consequently, 40 patients (78%) showed mechanical alternans. Mechanical alternans was always accompanied by alternating changes of positive dP/dt, a parameter of contractility during isovolumetric contraction time, but negative dP/dt was occasionally constant. Concordant mechanical alternans between both ventricles was more prevalent than discordant alternans. The left ventricular end-diastolic volume indices and end-systolic volume indices of patients with mechanical alternans were larger than those of patients without. The left ventricular ejection fraction of patients with alternans was significantly lower than that of patients without.</AbstractText>Mechanical alternans was highly prevalent in patients with chronic heart failure. The origin of mechanical alternans seems to exist before or at the isovolumetric contraction time.</AbstractText> |
3,883 | Novel mechanism for Brugada syndrome: defective surface localization of an SCN5A mutant (R1432G). | The SCN5A gene encodes the alpha subunit of the human heart sodium channel (hH1), which plays a critical role in cardiac excitability. Mutations of SCN5A underlie Brugada syndrome, an inherited disorder that leads to ventricular fibrillation and sudden death. This study describes changes in cellular localization and functional expression of hH1 in a naturally occurring SCN5A mutation (R1432G) reported for Brugada syndrome. Using patch-clamp experiments, we show that there is an abolition of functional hH1 expression in R1432G mutants expressed in human tsA201 cells but not in Xenopus oocytes. In tsA201 cells, a conservative positively charged mutant, R1432K, produced sodium currents with normal gating properties, whereas other mutations at this site abolished functional sodium channel expression. Immunofluorescent staining and confocal microscopy showed that the wild-type alpha subunit expressed in tsA201 cells was localized to the cell surface, whereas the R1432G mutant was colocalized with calnexin within the endoplasmic reticulum. The beta(1) subunit was also localized to the cell surface in the presence of the alpha subunit; however, in its absence, the beta(1) subunit was restricted to a perinuclear localization. These results demonstrate that the disruption of SCN5A cell-surface localization is one mechanism that can account for the loss of functional sodium channels in Brugada syndrome. The full text of this article is available at http://www.circresaha.org. |
3,884 | Evaluation of the role of I(KACh) in atrial fibrillation using a mouse knockout model. | We sought to study the role of I(KACh) in atrial fibrillation (AF) and the potential electrophysiologic effects of a specific I(KACh) antagonist.</AbstractText>I(KACh) mediates much of the cardiac responses to vagal stimulation. Vagal stimulation predisposes to AF, but the specific role of I(KACh) in the generation of AF and the electrophysiologic effects of specific I(KACh) blockade have not been studied.</AbstractText>Adult wild-type (WT) and I(KACh)-deficient knockout (KO) mice were studied in the absence and presence of the muscarinic receptor agonist carbachol. The electrophysiologic features of KO mice were compared with those of WT mice to assess the potential effects of a specific I(KACh) antagonist.</AbstractText>Atrial fibrillation lasting for a mean of 5.7+/-11 min was initiated in 10 of 14 WT mice in the presence of carbachol, but not in the absence of carbachol. Atrial arrhythmia could not be induced in KO mice. Ventricular tachyarrhythmia could not be induced in either type of mouse. Sinus node recovery times after carbachol and sinus cycle lengths were shorter and ventricular effective refractory periods were greater in KO mice than in WT mice. There was no significant difference between KO and WT mice in AV node function.</AbstractText>Activation of I(KACh) predisposed to AF and lack of I(KACh) prevented AF. It is likely that I(KACh) plays a crucial role in the generation of AF in mice. Specific I(KACh) blockers might be useful for the treatment of AF without significant adverse effects on the atrioventricular node or the ventricles.</AbstractText> |
3,885 | Postmarketing reports of QT prolongation and ventricular arrhythmia in association with cisapride and Food and Drug Administration regulatory actions. | To describe the postmarketing safety data used in the risk assessment of cisapride and to summarize the regulatory actions of the Food and Drug Administration (FDA).</AbstractText>The FDA analyzed reports of patients who developed QT prolongation, torsades de pointes, and ventricular arrhythmia in association with the use of cisapride to assess probable etiology and risk factors.</AbstractText>While cisapride was being marketed from 1993-1999, the FDA received reports of the following patients: 117 who developed QT prolongation; 107, torsades de pointes; 16, polymorphic ventricular tachycardia; 18, ventricular fibrillation; 27, ventricular tachycardia; 25, cardiac arrest; 16, serious (unspecified) arrhythmia; and 15, sudden death; for a total of 341 individual patients affected, following use of cisapride. Eighty (23%) of the 341 patients died. Deaths were directly or indirectly associated with an arrhythmic event. Factors that suggested an association with cisapride included a temporal relationship between use of cisapride and arrhythmia, the absence of identified risk factors and other explanations for arrhythmia in some patients, and cases of positive dechallenge and rechallenge. In most individuals, the arrhythmia occurred in the presence of risk factors (other drugs and/or medical conditions).</AbstractText>Postmarketing reports and pharmacokinetic and electrophysiological data provided evidence that cisapride is associated with the occurrence of QT prolongation and torsades de pointes. The risk of fatal arrhythmia with cisapride was believed to outweigh the benefit for the approved indication, treatment of nocturnal heartburn due to gastroesophageal reflux disease, leading to the drug's discontinuation in the United States.</AbstractText> |
3,886 | Caffeine-induced cardiac arrhythmia: an unrecognised danger of healthfood products. | We describe a 25-year-old woman with pre-existing mitral valve prolapse who developed intractable ventricular fibrillation after consuming a "natural energy" guarana health drink containing a high concentration of caffeine. This case highlights the need for adequate labelling and regulation of such products. |
3,887 | [The new international guidelines for cardipulmonary resuscitation: an analysis and comments on the most important changes]. | In August 2000, the American Heart Association and the European Resuscitation Council published the conclusions of the International Guidelines 2000 Conference on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care which contains both the new recommendations and an in-depth review. The discussions and drafting began at a conference in March 1999, followed by a second conference in September 1999, both attended by approx. 250 participants and another conference in February 2000 which was attended by approx. 500 participants. Review of the current state of science, discussion and final consensus continued subsequently via email, conference calls, fax, and personal conversation. During the entire process, scientists and resuscitation councils from all over the world participated, with participants from the United States comprising approx. 60%, and scientists from outside of the United States comprising approx. 40%. In order to ensure that the CPR recomendations are not dominated by any given nation or resuscitation council, most topics were reviewed and interpretated by two scientists from the United States and two scientists from outside of the United States. Accordingly, changes in these new CPR recommendations are the result of an evidence-based review by worldwide experts. The most important changes in the recommendations according to the authors are discontinuation of the pulse-check for lay people, 500 ml instead of 800-1200 ml tidal volume during bag-valve-mask ventilation (FiO2 > 0.4) of a patient with an unprotected airway, verifying correct endotracheal intubation with capnography and an esophageal detector, employing mechanical devices such as interposed abdominal compression CPR, vest CPR, active-compression-decompression CPR, and the inspiratory threshold valve (ITV) CPR as alternatives or adjuncts to standard manual chest compressions, defibrillation with < 200 Joule biphasic instead of with 200-360 Joule monophasic impulses, vasopressin (40 units) and epinephrine (1 mg) as comparable drugs to treat patients with ventricular fibrillation, amiodarone (300 mg) for shock-refractory ventricular fibrillation and intravenous lysis for patients who have suffered a stroke. |
3,888 | A novel mechanism associated with idiopathic ventricular fibrillation (IVF) mutations R1232W and T1620M in human cardiac sodium channels. | Two mutations associated with idiopathic ventricular fibrillation (IVF) are localized within extracellular loops between segments DIIIS1-S2 (R1232W) and DIVS3-S4 (T1620M) of the human cardiac sodium channel (hNav1.5) alpha-subunit. We studied wild-type hNav1.5 channels and hNav1.5 channels with the R1232W/T1620M double mutation expressed in Xenopus oocytes using the cell-attached macropatch technique. We demonstrate that these mutations destabilize the fast-inactivated state (described with a two-state first-order reaction model) by decreasing reaction valence, accelerating recovery, and slowing the onset of fast inactivation, collectively resulting in delayed decay of macroscopic currents. R1232W/T1620M mutations in hNav1.5 channels also significantly increase steady-state channel availability, indicating that mutated channels occupy the slow inactivated state less than hNav1.5 channels. Under the stress of repetitive depolarizing pulses, R1232W/T1620M channels demonstrate less use-dependent current reduction compared to wild-type channels. We propose that increased channel availability coupled with destabilized fast inactivation contributes to the pathological effect of R1232W/T1620M mutations, and leads to increased excitability of cardiac tissue in vivo. |
3,889 | Acute dyspnoea resulting from pulmonary oedema as the first sign of a phaeochromocytoma. | The day after undergoing neck dissection, a 42-year-old woman developed acute dyspnoea due to pulmonary oedema. Measurements with a Swan-Ganz catheter revealed not only cardiac depression but also a greatly increased peripheral vascular resistance: 5,400 dyn x s x cm(-5)/m2. A phaeochromocytoma with acute cardiac failure leading to pulmonary oedema was considered. Treatment with alpha- and beta-blockers was complicated by severe hypotension and later ventricular fibrillation. Mechanical ventilation was required for 6 days following resuscitation. Investigation of the urine subsequently showed greatly increased catecholamine concentrations, while imaging revealed bilateral adrenal tumours. Our case history shows that acute pulmonary oedema may be the presenting manifestation of a phaeochromocytoma. The pulmonary oedema resulted partly from backward failure following tachycardia, myocyte necrosis and the greatly increased peripheral vascular resistance, and partly from increased permeability of the capillary network in the lungs. |
3,890 | Five-year experience with implantation and follow-up of transvenous implantable cardioverter defibrillators: placing postimplant defibrillation threshold testing in perspective. | The rapid technological advancement in transvenous implantable cardioverter defibrillators (ICDs) has resulted in heterogeneous and often controversial approaches to follow-up procedures. The efficacy of postimplantation defibrillation threshold (DFT) testing with new-generation biphasic ICDs is unknown.</AbstractText>In this retrospective study, predischarge and postdischarge DFT protocols were compared to evaluate their safety and effect on adverse clinical events.</AbstractText>The study population consisted of 89 patients with 92 ICDs and 103 endovascular lead systems. Forty-four patients had DFT tests during implant and the predischarge period. Thirty patients had DFT tests during implant and the postdischarge period. Sixteen patients had only implant DFT data available. The follow-up period ranged from 3 days to 5.6 years.</AbstractText>Ninety-nine percent of patients had successful implants. Postimplant DFT tests detected potential problems in only 1% of asymptomatic patients. Thirty-six percent of patients with normal predischarge DFT tests had adverse clinical events compared with 18% in the postdischarge group. Patients with postimplant DFTs > 25 joules (J) and safety margins > or = 10 J had a lower incidence of adverse clinical events (p = 0.03) compared with those with safety margins < 10 J. An 11% malfunction rate was observed in ICD leads during the follow-up period.</AbstractText>DFT testing after implant is safe; however, routine postimplant DFT testing has limited value in assessing abnormalities in patients with the current generation of biphasic transvenous ICD devices. A 10-J safety margin was associated with a lower incidence of adverse clinical events in patients with DFTs > 25 J. Endovascular lead failure remains a significant problem with ICD systems requiring vigilant follow-up.</AbstractText> |
3,891 | [Prevention of complications: a forgotten aspect of therapy? arrhythmia complication in heart failure]. | Heart failure has a high prevalence in the western world: 1-1.5% in the general population and 2-5% in patients above 65 years old. The association with cardiac dysarrhythmia is very common: 20-30% of patients have atrial fibrillation and significant ventricular arrhythmias occur in 50%. The pathophysiology of cardiac arrhythmias is multifactorial, including reentry, increased automaticity and triggered activity. Several prognostic factors have been described in patients with coronary artery disease, however, the two more important are the functional class and the severity of left ventricular dysfunction. In order to prevent disarrhythmic complications, the appropriate treatment of heart failure and of the underlying cardiac disease are very important. Class III antiarrhythmic drugs and the implantable cardioverter-defibrillator are increasingly used as primary (in high risk patients) or secondary prophylactic agents. |
3,892 | Atrioventricular node modification in patients with chronic atrial fibrillation: role of morphology of RR interval variation. | This study evaluates the role of RR interval distribution pattern as an outcome predictor of radiofrequency (RF) modification of atrioventricular (AV) node in chronic atrial fibrillation (AF) and attempts to elucidate the likely mechanism of rate control.</AbstractText>Sixty-five patients with chronic AF underwent AV node modification. The RR interval distribution pattern was derived from 24-hour ECG recordings obtained before and after the procedure. The preablation pattern was bimodal (B) in 36 patients (55%) and unimodal (U) in 29 patients (45%). After the modification procedure, the B pattern shifted to U (78%) or became modified B (22%). The mean number of RF pulses delivered and the fluoroscopy time were n=8+/-5 and 24+/-11 minutes, respectively, in patients with B pattern versus n=18+/-7 and 45+/-17 minutes in patients with U pattern (P<0.001 for both). The location of successful ablation was posteroseptal and lower midseptal in 26 patients (81%) with B pattern versus 2 (13%) with U pattern (P<0.001). Mean and maximal ventricular rates and heart rate at peak exercise were reduced after the procedure in both groups (P<0.001 for all). Long-term success rate, AV block incidence, and pacemaker implantation rate were 89%, 0%, and 8%, respectively, in patients with B pattern versus 52% (P<0.001), 21% (P=0.006), and 48% (P<0.001) in patients with U pattern.</AbstractText>RF modification of the AV node is expected to be more effective, safe, and expeditious in patients with chronic AF and B RR interval distribution pattern. Posterior atrionodal input ablation may be the prevailing mechanism of rate control in these patients, whereas U-pattern patients may benefit from partial injury to the AV node.</AbstractText> |
3,893 | Evolving indications for permanent pacemakers. | New indications for permanent cardiac pacing have been developed in recent years, with numerous studies demonstrating improved clinical outcomes in a variety of disorders. Because hypertrophic obstructive cardiomyopathy, dilated cardiomyopathy, heart failure, neurocardiogenic syncope, and atrial fibrillation are common conditions, every clinician should be aware of evolving alternative therapies for them. Observational studies in patients with refractory, symptomatic hypertrophic obstructive cardiomyopathy and significant left ventricular outflow gradient at rest suggest that cardiac pacing may result in symptomatic and hemodynamic improvement. Clinical trials have not shown conclusive evidence regarding the long-term benefit from pacing in these patients, and it is unclear whether pacing will be a preferred treatment option. Preliminary data suggest that pacing is a viable adjunctive therapeutic approach for improving symptoms in patients with dilated cardiomyopathy and heart failure. Mortality benefit has yet to be established, but it is to be hoped that ongoing randomized clinical trials will provide definitive information on that issue. Patients with refractory neurocardiogenic syncope or those who are intolerant of medical treatment may benefit from pacing therapies, especially those that use rate-drop sensor algorithms. Biatrial pacing has emerged as a technique that resynchronizes atrial electrical activity and has been shown to prevent atrial fibrillation. Multisite atrial pacing for the prevention of atrial fibrillation is considered investigational but seems promising. Newer indications for pacing are expected to result in improved clinical outcomes for hypertrophic obstructive cardiomyopathy, dilated cardiomyopathy and heart failure, neurocardiogenic syncope, and the prevention of atrial fibrillation. |
3,894 | Defibrillation and the geometry of the heart: a novel measurement with implications for defibrillation mechanisms. | We present a novel measurement for studying defibrillation mechanisms: the time course of changes in the size of the left ventricular (LV) cavity within 500 ms following defibrillation. Mechanical changes can be linked to electrical mechanisms via an understanding of excitation-contraction coupling. Eight mongrel dogs were internally defibrillated 5-50 seconds (including backup shocks) after the onset of 20 ventricular fibrillation (VF) episodes per animal. Two dimensional, short axis, LV cavity, ultrasound images were recorded at 30 frames per second just prior to inducing VF, during defibrillation and following the shock. Each frame was individually analysed to yield the LV cavity area as a function of time. Defibrillation shocks were followed by a highly reproducible phenomenon: (1) a dramatic and rapid increase in LV area, (2) a more or less prominent LV area plateau and (3) a decrease in the LV area. The peak fractional area increase ranged from 1.65 to 4.64 times larger than the baseline (LV area just prior to defibrillation), averaging 2.18 +/- 0.686. Successful shocks took significantly longer (p < 0.01) to return to 1.3 times the baseline (407 +/- 209 ms) than unsuccessful shocks (296 +/- 130 ms). Extrapolating to electrical mechanisms, our novel measurement demonstrates that defibrillation causes immediate relaxation and therefore suggests a significant role for deexcitation in defibrillation. |
3,895 | Noise sensitivity of three surface ECG fibrillation detection algorithms. | The widening application of automatic external defibrillators (AEDs) presents very strong requirements for external electrocardiogram (ECG) signal analysis. Highly accurate detection of shockable rhythms is required, aimed to approach the maximum of 100% sensitivity and specificity. In a previous study the performance of five well known detection algorithms was assessed by test signals from the ECG-signal databases of the American Heart Association (AHA) and the Massachusetts Institute of Technology (MIT). The results obtained were used as a basis for testing the noise sensitivity of three of these algorithms. Realistic noise was obtained by simulation and recording of signal disturbance by various motions during resuscitation and defibrillation episodes (body shudder convulsions and gasps, cable movement, car transportation). The sensitivity and specificity of the detection algorithms were evaluated using electrocardiogram signals mixed with these noises. |
3,896 | Catheter ablation of a monofocal premature ventricular complex triggering idiopathic ventricular fibrillation. | A 62 year old man was admitted for evaluation of recurrent episodes of syncope. A surface ECG showed frequent repetitive premature ventricular complexes of right ventricular outflow tract origin. Ventricular fibrillation was inducible by programmed electrical stimulation but otherwise cardiac evaluation was unremarkable. A diagnosis of idiopathic ventricular fibrillation was made and an implantable cardioverter-defibrillator (ICD) was installed. However, spontaneous ventricular fibrillation recurred, requiring repeated ICD discharges. The ventricular fibrillation was reproducibly triggered by a single premature ventricular complex with a specific QRS morphology. Radiofrequency catheter ablation was carried out to eradicate this complex. No ventricular fibrillation has developed after this procedure, and the patient does not require drug treatment. |
3,897 | Effect of levosimendan on myocardial contractility, coronary and peripheral blood flow, and arrhythmias during coronary artery ligation and reperfusion in the in vivo pig model. | To determine whether levosimendan, a calcium sensitiser that facilitates the activation of the contractile apparatus by calcium, improves myocardial contractile function during severe ischaemia and reperfusion without exacerbating the incidence of arrhythmias.</AbstractText>Pigs were pretreated orally twice daily for 10 days with 0.08 mg/kg levosimendan or placebo. On day 11 the left main coronary artery was ligated for 30 minutes, followed by 30 minutes of reperfusion. A bolus dose of levosimendan, 11.2 microg/kg intravenously, or placebo was given 30 minutes before coronary ligation, followed by a continuous infusion of 0.2 microg/kg/min levosimendan or placebo for the remainder of the experiment.</AbstractText>During the ischaemic period, cardiac output was higher in the levosimendan group than in the placebo group (mean (SD): 2.6 (0.5) v 2.0 (0.2) l/min, p < 0.05) and systemic vascular resistance was lower (2024 (188) v 2669 (424) dyne.s(-1).cm(-5), p < 0.005). During reperfusion, cardiac output and contractility (LV(max)dP/dt (pos), 956 (118) v 784 (130) mm Hg/s, p < 0.05) were increased by levosimendan. The incidence of ischaemic ventricular fibrillation and tachycardia was similar in the two groups but there were more arrhythmic events (ventricular tachycardia and ventricular fibrillation) in the levosimendan treated group (8/12 levosimendan v 1/9 control p = 0.05).</AbstractText>Levosimendan improved cardiac output and myocardial contractility during coronary artery ligation and reperfusion. However, it increased the number of arrhythmic events during ischaemia in this model of in vivo regional ischaemia.</AbstractText> |
3,898 | Patterns of wave break during ventricular fibrillation in isolated swine right ventricle. | Several different patterns of wave break have been described by mapping of the tissue surface during fibrillation. However, it is not clear whether these surface patterns are caused by multiple distinct mechanisms or by a single mechanism. To determine the mechanism by which wave breaks are generated during ventricular fibrillation, we conducted optical mapping studies and single cell transmembrane potential recording in six isolated swine right ventricles (RV). Among 763 episodes of wave break (0.75 times x s(-1) x cm(-2)), optical maps showed three patterns: 80% due to a wave front encountering the refractory wave back of another wave, 11.5% due to wave fronts passing perpendicular to each other, and 8.5% due to a new (target) wave arising just beyond the refractory tail of a previous wave. Computer simulations of scroll waves in three-dimensional tissue showed that these surface patterns could be attributed to two fundamental mechanisms: head-tail interactions and filament break. We conclude that during sustained ventricular fibrillation in swine RV, surface patterns of wave break are produced by two fundamental mechanisms: head-tail interaction between waves and filament break. |
3,899 | What niche will newer class III antiarrhythmic drugs occupy? | The decline in the use of sodium channel blockers has led to an expanding use of b-blockers and complex class III agents such as sotalol and amiodarone for controlling cardiac arrhythmias. Success with these agents in the context of their side effects has spurred the development of compounds with simpler ion channel-blocking properties with less complex adverse reactions. The resulting so-called pure class III agents were found to have antifibrillatory effects in atrial fibrillation (AF) and flutter, as well as in ventricular tachyarrhythmias. Pure class III compounds are effective in inducing acute chemical conversion of AF, in preventing paroxysmal AF, and in maintaining sinus rhythm in patients with persistent AF restored to sinus rhythm. Examples of such compounds are dofetilide, which selectively blocks IKr, and ibutilide, available only as an intravenous agent, which blocks the IKr and augments the inactivated Na+ current in atrial myocytes. Dofetilide and ibutilide have been introduced into clinical practice. Azimilide is the first of the class III agents that blocks both components (IKr and IKs) of the delayed rectifier current, which may confer certain electrophysiologic advantages. The potential therapeutic niche of ibutilide, dofetilide, and azimilide in the control of cardiac arrhythmias forms the basis of this review. |
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