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3,900 | Should patients with asymptomatic wolff-parkinson-white pattern undergo a catheter ablation? | Many individuals with the Wolff-Parkinson-White electrocardiographic pattern are asymptomatic. Optimal management of these individuals is still a matter of debate. On the one hand, sudden cardiac death from ventricular fibrillation is a rare yet possible outcome in these individuals. On the other hand, there is a low risk of serious complication from electrophysiologic study and ablation. Given that the risk of these competing strategies is comparable, the decision needs to be individualized with considerable patient input. |
3,901 | Biventricular pacing therapy for congestive heart failure: a review of the literature. | Biventricular pacing is a new therapy for patients with congestive heart failure and mechanical dyssynchrony. Its therapeutic intent is to activate both ventricles simultaneously, thus improving the mechanical efficiency of the ventricles. Preliminary evidence indicates improvement in hemodynamics, quality of life, and exercise capacity in patients in sinus rhythm as well as in patients with atrial fibrillation. An improvement in diastolic filling, a decrease in mitral regurgitation, and more efficient systolic ejection are proposed as the mechanisms behind these benefits. In addition, some evidence indicates that the frequency of ventricular arrhythmias is decreased. All clinicians involved in the management of patients with congestive heart failure eagerly await the results of ongoing trials. The results of these trials will define which patients are eligible for this therapy, which patients will derive the most benefit from it, and its effect on morbidity and mortality. |
3,902 | Myocardial ischemia: what factors determine arrhythmogenesis? | In ischemic myocardium, cellular architecture and heterogeneous changes in metabolic and ionic conditions interact to cause spatial and temporal heterogeneity of electrical properties predisposing to lethal ventricular arrhythmias. Yet, the details of their interaction, vis-à-vis the initiation and maintenance of reentry, remain poorly understood. Future studies are needed to address the mechanisms of the initial premature beat, reentry, and formation of wavebreaks contributing to ventricular fibrillation. New experimental methods including mathematical and transgenic mouse models are promising techniques to study these phenomena and thereby provide new insights into the fundamental mechanisms of ischemia-related arrhythmias. |
3,903 | Excitable gap in canine fibrillating ventricular myocardium: effect of subacute and chronic myocardial infarction. | The existence of an excitable gap during ventricular fibrillation (VF) has been suggested in several prior studies. However, the effects of myocardial infarction on the presence and duration of an excitable gap during VF have not been evaluated.</AbstractText>Electrophysiologic study was performed in normal dogs and in dogs with subacute and chronic infarction. Experimental infarction was produced by left anterior descending coronary ligation. The excitable gap was determined indirectly using either evaluation of intrinsic wavefronts during VF or from the shortest activation interval at individual sites using recordings from a 112-electrode plaque sutured to the epicardial surface of the left ventricle. The excitable gap also was correlated to local electrophysiologic and anatomic properties. The excitable gap using the wavefront propagation method and shortest activation method was significantly longer in subacute infarction dogs (48 +/- 17 msec and 37 +/- 18 msec, respectively) and chronic infarction dogs (41 +/- 14 msec and 35 +/- 14 msec, respectively) than normal dogs (32 +/- 13 msec and 30 +/- 11 msec, respectively; P < 0.05 normal vs subacute and chronic infarction dogs in both methods). The excitable gap occupied approximately 30% and 27% of the VF cycle length in all three groups using the wavefront propagation and shortest activation method, respectively. The excitable gap correlated better with local ventricular refractoriness determined using the wavefront propagation method than with the shortest activation method, but not at all with refractoriness determined using extrastimulus testing. Tissue necrosis was noted in subacute infarction dogs and fibrosis in chronic infarction dogs, but the gap was not highly correlated with anatomic changes.</AbstractText>During VF, an excitable gap exists in both normal and infarcted canine ventricular myocardium. It is significantly longer in the presence of infarction. These finding have implications for understanding the pathophysiology of VF and targeting antiarrhythmic therapies.</AbstractText> |
3,904 | Brugada syndrome and supraventricular tachyarrhythmias: a novel association? | The Brugada syndrome is a distinct form of idiopathic ventricular fibrillation characterized by a unique ECG pattern consisting of a right bundle branch block-like aspect and ST segment elevation in leads V1 to V3. As a high induction rate of ventricular tachyarrhythmias has been reported in Brugada syndrome, we hypothesized that this also may be true for supraventricular tachycardias in these patients.</AbstractText>Between January 1995 and December 2000, we identified 35 consecutive patients with Brugada syndrome; 26 had a history of cardiac arrest or syncope and 9 were asymptomatic. All patients underwent electrophysiologic study, including an atrial and ventricular stimulation protocol. Ten patients (29%) were found to have supraventricular tachyarrhythmias (SVT) in addition to the Brugada syndrome. These 10 patients presented with aborted sudden cardiac death (n = 3) and/or a family history of sudden cardiac death (n = 4), syncope (n = 4), or primarily with a Brugada typical ECG, a positive family history, and palpitations (n = 2). Eight of them underwent genetic testing, but only 1 had a mutation in the SCN5A gene. In 6 patients, an AV nodal reentrant tachycardia was easily and reproducibly inducible. Two patients had clinical documented and inducible episodes of an atrial tachycardia (1 in addition to an AV nodal reentrant tachycardia). One patient had paroxysmal atrial fibrillation alternating with sinus rhythm, and 2 patients with accessory pathways were identified.</AbstractText>This is the first description of an association of the Brugada syndrome with SVT. Thus, the arrhythmogenic substrate in Brugada syndrome may not be restricted to the ventricular level. Palpitations in this syndrome should raise the possibility of SVT. Conversely, in patients with SVT and aborted sudden cardiac death or syncope not related to SVT, the Brugada syndrome should be considered a possible additional electrophysiologic abnormality.</AbstractText> |
3,905 | Dissociation between coronary sinus and left atrial conduction in patients with atrial fibrillation and flutter. | Coronary sinus (CS) recordings are routinely used during electrophysiologic studies for various supraventricular and ventricular arrhythmias with the understanding that they represent left atrial (LA) activity. However, the behavior of CS electrical activity during atrial arrhythmias has not drawn any special attention beyond standard considerations.</AbstractText>The study population consisted of 9 patients (3 women; mean age 59 +/- 11 years) with atrial fibrillation (AF) and atrial flutter (AFL) who developed dissociation of conduction between the CS and posterior LA during spontaneous AF and AFL. In all patients, the LA and the CS were mapped using a 64-electrode basket catheter and a multipolar electrode catheter, respectively. The right atrium (RA) was mapped simultaneously using a 24-polar electrode catheter (7 patients) or a 64-electrode basket catheter (2 patients). Eight patients showed stable double potentials in CS recordings during AF (9 episodes) and AFL (3 episodes). During ongoing arrhythmias, the first row of potentials maintained a constant relationship with the RA activity, whereas the second row of potentials was discordant with the posterior wall of the LA in 7 patients and concordant in 2 patients. In 1 patient with counterclockwise AFL, CS activation was isolated from the posterior wall of the RA until it reached the distal portion of the CS, after which it entered the lateral region of the LA. In 1 patient, a macroreentrant LA tachycardia involving CS muscle was observed. Rapid atrial pacing from the proximal CS and extrastimuli produced longitudinal dissociation of CS activation in all patients.</AbstractText>Conduction between the CS and posterior LA can be dissociated during spontaneous atrial arrhythmias and provocative proximal CS pacing.</AbstractText> |
3,906 | Early angiographic control of perioperative ischemia after coronary artery bypass grafting. | To assess the impact of immediate angiography in patients with defined clinical and laboratory criteria of perioperative myocardial infarction after coronary artery bypass operation.</AbstractText>Between January 1999 and December 1999 2052 patients underwent coronary artery bypass grafting in our institution. Out of this cohort 131 (6.4%) patients met the criteria of perioperative myocardial ischemia, which was defined as: (a) increase in the isoenzyme ratio of creatinine phosphokinase (CK/CK-MB] above 10%; (b) ischemic electrocardiographic episodes (defined as a new onset of elevated ST-segment change lasting at least 1 min and involving a shift from baseline of greater than or equal to 0.1 mV of ST-depression and a new association of a postoperative Q; (c) recurrent episodes of, or sustained ventricular tachyarrhythmia as well as ventricular fibrillation; (d) hemodynamic deterioration despite adequate inotropic support.</AbstractText>Angiography was performed in 108 patients (5.3%, group A) whereas 23 patients (1.1%, group B) were immediately re-operated due to severely compromised hemodynamics. Angiographic results in group A showed regular grafts in 45 patients (2.2%); 63 patients (3.1%) had either an occlusion (n=41), incorrect anastomosis (n=29), graft stenosis (n=14), graft spasm (n=6), displaced graft (n=6), poor distal run-off (n=5) or incomplete revascularization (n=2). In group A 43 patients underwent a re-operation (34 patients) or an early angioplasty (nine patients). Due to poor coronary artery status no intervention was performed in the remaining 20 patients with angiographic findings. Operative findings in group B showed graft occlusion in ten patients (43.5%), incorrect anastomosis in five patients (21.7%), bleeding, stretched graft, venous graft spasm and displaced graft in one patient (4.3%) each, and no patho-morphological finding in 4 patients (17.4%). Thirty-day mortality rate was ten patients in group A (9.3%), all of them with angiographic findings, as opposed to nine patients (39.1%) in group B.</AbstractText>ST-change and elevated CK/CK-MB enzyme ratio is highly indicative for possible graft failure and should be followed early angiographic control to assess the need for reintervention.</AbstractText> |
3,907 | Polymorphic ventricular tachycardia in patients with vasospastic angina--clinical and electrocardiographic characteristics and long-term outcome. | There have been few clinical studies exploring the characteristics of spontaneous polymorphic ventricular tachycardia (VT) during a vasospastic angina attack. During a 4-year recruitment period, Holter ECG recordings were monitored for 42+/-24 h during a drug-free period in 60 consecutive patients with vasospastic angina (VSA) and of these, 8 patients had at least one episode of polymorphic VT during monitoring. Ischemic ST segment elevation was immediately preceded the spontaneous polymorphic VT in all 8 patients, 4 of whom had silent coronary vasospasm. Immediately before the onset of polymorphic VT, both R-on-T and long-short sequences were observed in 4 of the 8 patients and ST wave alternans were recorded in 2 patients. VT exhibited a pattern of torsade de pointes in 4 of the 8 patients. Five patients underwent electrophysiologic testing during a drug-free asymptomatic phase, and polymorphic VT was induced in 2 of the 5 patients, with one developing ventricular fibrillation. During a follow-up period of 73+/-17 months, there was a significant difference in the incidence of sudden death between patients with and without VT (2/8 cases [25%] vs 0/52 [0%]; p<0.01). Thus, vasospastic attacks, even if asymptomatic, that immediately precede the development of polymorphic VT may be associated with a repolarization abnormality and an increased risk of sudden death. |
3,908 | Arrhythmias in patients with Brugada-type electrocardiographic findings. | Brugada syndrome is characterized by marked ST-segment elevation in the right precordial leads (Bru-ECG) and is associated with a high risk for sudden death. However, it is unclear whether the arrhythmogenesis is caused by the mechanisms responsible for Bru-ECG. The present study investigated the risk of arrhythmias in patients with Bru-ECG by retrospectively analyzing 30 patients (28 men; mean age, 51+/-14 years) with Bru-ECG. Aborted sudden cardiac death (ventricular fibrillation or syncope) occurred in 9 patients (30%); paroxysmal atrial fibrillation was present in 9 (30%) patients in addition to malignant ventricular arrhythmias, and some type of arrhythmic event (aborted sudden cardiac death or paroxysmal atrial fibrillation) occurred in 15 patients (50%). Of all the arrhythmic events, 93% occurred at night or early in the morning, and 92% had pronounced ST-segment elevation. These results suggest that Bru-ECG may be associated not only with an increased risk of ventricular tachyarrhythmias but also with an increased risk of paroxysmal atrial fibrillation, and that the arrhythmogenesis may be related to the pronounced ST-segment elevation. |
3,909 | Electrophysiological characterization of murine myocardial ischemia and infarction. | Genetically altered mice will provide important insights into a wide variety of processes in cardiovascular physiology underlying myocardial infarction (MI). Comprehensive and accurate analyses of cardiac function in murine models require implementation of the most appropriate techniques and experimental protocols.</AbstractText>In this study we present in vivo, whole-animal techniques and experimental protocols for detailed electrophysiological characterization in a mouse model of myocardial ischemia and infarction.</AbstractText>FVB mice underwent open-chest surgery for ligation of the left anterior descending coronary artery or sham-operation. By means of echocardiographic imaging, electrocardiography, intracardiac electrophysiology study, and conscious telemetric ECG recording for heart rate variability (HRV) analysis, we evaluated ischemic and post-infarct cardiovascular morphology and function in mice.</AbstractText>Coronary artery ligation resulted in antero-apical infarction of the left ventricular wall. MI mice showed decreased cardiac function by echocardiography, infarct-typical pattern on ECG, and increased arrhythmia vulnerability during electrophysiological study. Electrophysiological properties were determined comprehensively, but were not altered significantly as a consequence of MI. Autonomic nervous system function, measured by indices of HRV, did not appear altered in mice during ischemia or infarction.</AbstractText>Cardiac conduction, refractoriness, and heart rate variability appear to remain preserved in a murine model of myocardial ischemia and infarction. Myocardial infarction may increase vulnerability to inducible ventricular tachycardia and atrial fibrillation, similarly to EPS findings in humans. These data may be of value as a reference for comparison with mutant murine models necessitating ischemia or scar to elicit an identifiable phenotype. The limitations of directly extrapolating murine cardiac electrophysiology data to conditions in humans need to be considered.</AbstractText> |
3,910 | Three-year follow-up of patients with right bundle branch block and ST segment elevation in the right precordial leads: Japanese Registry of Brugada Syndrome. Idiopathic Ventricular Fibrillation Investigators. | We sought to determine the prevalence of right bundle branch block (RBBB) and ST segment elevation in the working Japanese population, as well as the event rate during a three-year prospective follow-up period.</AbstractText>A poor prognosis of RBBB and ST segment elevation has been reported in Europe and South America, even in asymptomatic patients; however, a large population of asymptomatic patients with sporadic RBBB and ST segment elevation has not been studied.</AbstractText>Ten thousand 12-lead electrocardiograms (ECGs) were obtained during annual check-ups of working adults in the Tokyo area. This three-year prospective follow-up study consisted of 105 patients, including 20 with ventricular fibrillation, 18 with syncope and 67 who were asymptomatic. They were registered from 46 institutions in Japan.</AbstractText>The prevalence of ECG abnormalities in working adults was 0.16%. A coved-type ST segment elevation was related to a history of cardiac events, and 18% of registered patients had PR prolongation and 9.5% had left-axis deviation. The cumulative cardiac event-free rate was 67.6% in the symptomatic group and 93.4% in the asymptomatic group (p = 0.0004) after three years.</AbstractText>The recurrence rate of cardiac events in symptomatic patients was similar to that reported previously, but it was very low in sporadic asymptomatic patients. The ECG findings may help us to select patients for further examination and more accurate evaluation of their prognoses.</AbstractText> |
3,911 | Recurrence of symptomatic ventricular arrhythmias in patients with implantable cardioverter defibrillator after the first device therapy: implications for antiarrhythmic therapy and driving restrictions. CARE Group. | The purpose of this study was to investigate whether clinical or electrophysiologic characteristics could predict initial and subsequent implantable cardioverter defibrillator (ICD) therapy.</AbstractText>Identification of markers to predict subsequent ICD therapy and symptoms after the first event could affect patient management.</AbstractText>We analyzed baseline and follow-up data on 125 ICD patients followed for 408+/-321 days. Medications and ICD programming were not changed after first ICD therapy.</AbstractText>Implantable cardioverter defibrillator therapy occurred in 58 patients (46%). Clinical features were as follows: mean left ventricular ejection fraction (LVEF) 29%+/-15%; coronary artery disease 84%; presenting arrhythmia with sustained monomorphic ventricular tachycardia (SMVT) in 68%. In a multivariate analysis the relative risk for ICD therapy in patients presenting with SMVT versus cardiac arrest (CA) was 2.57 (range, 1.32 to 5.01), and for patients with LVEF < or =25%, 1.95 (1.11 to 3.45), respectively (p < 0.05). Implantable cardioverter defibrillator therapy was not predicted by any other variable. Forty-six patients had second ICD therapy. Mean time to second ICD therapy was only 66+/-93 days compared with 138+/-168 days for first ICD therapy (p < 0.05). No predictor for second ICD therapy was found. Regarding symptoms, impaired consciousness during initial ICD therapy was predicted only by SMVT cycle length <250 ms at electrophysiologic testing. In contrast, symptoms were similar between first and second ICD therapy (p = 0.0001). Of note, ventricular tachycardia cycle length preceding first and second ICD therapy was similar (r = 0.76, p = 0.001).</AbstractText>First ICD therapy tends to occur in patients presenting with SMVT and LVEF < or =25%. Subsequent therapy occurs sooner and is unpredictable, suggesting that antiarrhythmic drug therapy should be considered after the first symptomatic ICD therapy. Symptoms during first ICD therapy predict subsequent symptoms, and patients presenting with SMVT and asymptomatic first ICD therapy are at very low risk for future syncopal ICD therapy.</AbstractText> |
3,912 | [Congenital long QT syndrome]. | Long QT syndrome (LQTS) is a clinically and genetically heterogenous syndrome characterized by a lengthening of the QT interval on the surface ECG and a propensity to severe ventricular arrhythmias such as torsades de pointes and ventricular fibrillation, leading eventually to syncope and sudden death. This rare syndrome with a mendelian inheritance occurs in subjects with otherwise normal cardiac morphological examination. The potentially severe prognosis justifies a presymptomatic diagnosis. The genetic nature of the disease has been confirmed with the identification of at least six loci and five genes. This syndrome is a perfect illustration of an adrenergic-induced ventricular arrhythmia. The first-line treatment is a beta-blocking agent for all symptomatic patients. In addition, a number of drugs known to lengthen ventricular repolarization must be prohibited. In case of suspicion of LQTS, all family members should be tested both clinically with a surface ECG and genetically in order to diagnose presymptomatic patients. |
3,913 | Combined phosphodiesterase inhibition and beta-blockade in the GI104313, decreases ischemia-induced arrhythmias in the rat. | The purpose of the present study was to evaluate the effects of GI104313, a chimeric molecule containing a phosphodiesterase inhibiting pyradazinone and a blocking phenoxpropanolamine, on ischemia-induced arrhythmias in anesthetized rats.</AbstractText>The coronary artery was occluded 15 min after commencing drug administration and myocardial ischemia was maintained for 30 min during which the heart rate and mean blood pressure were recorded. Cyclic AMP and GMP were determined by radio-immunoassay.</AbstractText>GI104313 (0.1 micromol x kg(-1) plus 0.01 micromol x kg(-1) x min(-1) or 1 micromol x kg(-1) plus 0.1 micromol x kg(-1) x min(-1)) decreased the incidence of ventricular tachycardia (86% and 75%), ventricular fibrillation (28%, P <0.01 and 12%, P <0.001) and premature ventricular beats (164 +/- 27.0 and 114 +/- 28.5, P <0.05) following coronary artery ligation, resulting in a decrease in mortality (29% and 12%, P <0.05). Changes in cyclic nucleotide concentrations have been implicated in the genesis of ischemia-induced arrhythmias. However, in the present study GI104313 did not change the concentrations of adenosine 3':5'-cyclic monophosphate (cyclic AMP) (1.0 +/- 0.07 pmol x mg(-1), 1.0 +/- 0.05 pmol x mg(-1)) or guanosine 3':5'-cyclic monophosphate (cyclic GMP) (0.025 +/- 0.008 pmol x mg(-1) protein, 0.017 +/- 0.004 pmol x mg(-1) protein) in the left ventricle during ischemia-induced arrhythmias in anesthetized rats compared to saline (0.9 +/- 0.1 pmol x mg(-1) and 0.013 +/- 0.002 pmol x m(-1), respectively).</AbstractText>Our results demonstrate that, in rats, GI104313 induced a decrease in both incidence of arrhythmias and mortality which was not associated with changes in ventricular cyclic nucleotide content.</AbstractText> |
3,914 | Serious arrhythmias in patients with apical hypertrophic cardiomyopathy. | We report cases of serious arrhythmias associated with apical hypertrophic cardiomyopathy (AHCM). Thirty-one patients were referred to our institute to undergo further assessment of their AHCM from 1988 to 1999. Three patients with nonsustained ventricular tachycardia demonstrated an 123I-MIBG regional reduction in the tracer uptake. In two patients with ventricular fibrillation (VF), the findings from 123I-MIBG imaging revealed regional sympathetic denervation in the inferior and lateral regions. Electrophysiologic study demonstrated reproducible induction of VF in aborted sudden death and presyncopal patients, resulting in the need for an implantable defibrillator device and amiodarone in each patient. Patients with refractory atrial fibrillation with a rapid ventricular response suffered from serious congestive heart failure. A prudent assessment and strategy in patients with this disease would be indispensable in avoiding a disastrous outcome. |
3,915 | Inappropriate detection of supraventricular arrhythmias by implantable dual chamber defibrillators: a comparison of four different algorithms. | Inappropriate therapy of supraventricular tachyarrhythmias by an ICD is still a common problem. Dual chamber (DDD) ICDs provide additional atrial sensing and should result in higher specificity for detection of supraventricular tachyarrhythmias. However, a direct comparison of different dual chamber algorithms has not been reported. The detection algorithms of four different DDD ICDs were tested: Phylax AV, Defender IV, Ventak AV III DR, and Gem DR 7271. Based on arrhythmias recorded from patients undergoing invasive electrophysiological studies and in many cases of catheter ablation at our institution, a library consisting of 71 supraventricular and 15 ventricular tachyarrhythmias was created. The library consists of episodes of atrial fibrillation, atrial flutter with different AV conduction, typical and atypical AV nodal reentrant tachycardia, AV reentrant tachycardia, sinus tachycardia, and ventricular tachycardia with and without ventriculoatrial conduction. Atrial fibrillation was appropriately classified by all four algorithms. However, the specificity for detection of other supraventricular tachyarrhythmias achieved by the Biotronik (12%) and the Guidant (11%) devices was significantly lower compared to the specificity of the ELA (28%) and the Medtronic DDD ICD (20%). This is due to the fact that the Biotronik and the Guidant algorithm classified all supraventricular tachyarrhythmias resulting in a stable ventricular rate as ventricular tachycardia, whereas the ELA and Medtronic algorithms performed a more detailed analysis by assessment of PR association, atrial onset, or timing of the atrial event relative to the ventricular event, respectively. Atrial fibrillation, the most common supraventricular tachyarrhythmia in patients with ICD, was detected by all devices. |
3,916 | Supraventricular tachycardia-ventricular tachycardia discrimination algorithms in implantable cardioverter defibrillators: state-of-the-art review. | To reduce inappropriate therapy of supraventricular tachycardia (SVT), implantable cardioverter defibrillators (ICDs) include algorithms to discriminate ventricular tachycardia (VT) from SVT. Dual-chamber algorithms analyze atrial and ventricular rates or AV relationship. They provide advantages over single-chamber algorithms, but introduce new ways to detect SVT as VT inappropriately and to underdetect VT. Unlike pacemakers, dual-chamber ICDs require accurate atrial sensing during high ventricular rates. A postventricular atrial blanking period prevents oversensing of far-field R waves as atrial electrograms, but causes underdetection of atrial fibrillation during high ventricular rates. Tachycardias with 1:1 AV relationship and VT during atrial tachyarrhythmias present specific SVT-VT discrimination problems. The first dual-chamber algorithms performed comparably to single-chamber algorithms. Present dual-chamber algorithms correct some limitations of earlier versions. |
3,917 | Reentry site during fibrillation induction in relation to defibrillation efficacy for different shock waveforms. | Unsuccessful defibrillation shocks may reinitiate fibrillation by causing postshock reentry.</AbstractText>To better understand why some waveforms are more efficacious for defibrillation, reentry was induced in six dogs with 1-, 2-, 4-, 8-, and 16-msec monophasic and 1/1- (both phases 1 msec) 2/2-, 4/4-, and 8/8-msec biphasic shocks. Reentry was initiated by 141+/-15 V shocks delivered from a defibrillator with a 150-microF capacitance during the vulnerable period of paced rhythm (183+/-12 msec after the last pacing stimulus). The shock potential gradient field was orthogonal to the dispersion of refractoriness. Activation was mapped with 121 electrodes covering 4 x 4 cm of the right ventricular epicardium, and potential gradient and degree of recovery of excitability were estimated at the sites of reentry. Defibrillation thresholds (DFTs) were estimated by an up-down protocol for the same nine waveforms in eight dogs internally and in nine other dogs externally. DFT voltages for the different waveforms were positively correlated with the magnitude of shock potential gradient and negatively correlated with the recovery interval at the site at which reentry was induced by the waveform during paced rhythm for both internal (DFT = 1719 + 64.5VV - 11.1RI; R2 = 0.93) and external defibrillation (DFT = 3445 + 150VV - 22RI; R2 = 0.93).</AbstractText>The defibrillation waveforms with the lowest DFTs were those that induced reentry at sites of low shock potential gradient, indicating efficacious stimulation of myocardium. Additionally, the site of reentry induced by waveforms with the lowest DFTs was in myocardium that was more highly recovered just before the shock, perhaps because this high degree of recovery seldom occurs during defibrillation due to the rapid activation rate during fibrillation.</AbstractText> |
3,918 | Critically timed auxiliary shock to weak field area lowers defibrillation threshold. | This study tested the hypothesis that the defibrillation threshold (DFT) can be lowered by delivering a weak auxiliary shock in conjunction with a stronger primary shock to the cardiac region where the primary shock electric field is weakest.</AbstractText>Eight swine were studied in each of two study parts. In both parts, DFTs were determined for dual shocks delivered through two electrode pairs. The biphasic primary shock was delivered through electrodes in the right ventricle and superior vena cava. The auxiliary shock was delivered through a separate electrode in the superior vena cava and a left ventricular electrode placed where the primary shock field was presumed to be weakest. In part I, a monophasic auxiliary shock of 50, 100, or 150 V was delivered either simultaneously with or 1, 20, or 40 msec before primary shock. When auxiliary shock was delivered simultaneously with or 1 msec before primary shock, DFT energy was reduced by approximately 50% compared with primary shock alone. In part II, a 150-V monophasic or biphasic auxiliary shock of either polarity was delivered 1 msec before or after primary shock. Regardless of waveform or polarity, all auxiliary shock delivered before primary shock lowered DFT energy by approximately 30% compared with primary shock alone. Depending on waveform and polarity, auxiliary shock delivered after primary shock either did not significantly change the DFT or elevated the DFT compared with primary shock alone.</AbstractText>Application of a small auxiliary shock, just before or simultaneously with a primary shock, to the cardiac region where the primary shock field is weakest significantly lowers DFT.</AbstractText> |
3,919 | Female gender is a risk factor for drug-induced long QT and cardiac arrhythmias in an in vivo rabbit model. | Clinical observations and in vitro experimental data indicate that females have a longer QT interval than males, which is associated with a higher risk of drug-induced cardiac arrhythmias. Little is known about this gender difference in anesthetized animals, which may affect the outcome of in vivo drug tests.</AbstractText>We evaluated potential gender differences in ventricular repolarization (QT, QTc, JT, and JTc interval) and its dispersion, as well as in its response to dofetilide, an IKr blocker, in anesthetized rabbits challenged with the alpha1-adrenoceptor agonist methoxamine. A 12-lead ECG was recorded during the experiments. At baseline, there were no significant gender differences in ventricular repolarization values in male and female rabbits under anesthesia. Dofetilide (0.04 mg/kg/min IV for 60 min; n = 10 per gender) produced marked prolongation of the ventricular repolarization time and its dispersion, associated with a high incidence of polymorphic ventricular tachycardia (PVT; 100% in females vs 80% in males) and ventricular fibrillation (VF; 80% in females vs 50% in males; P > 0.05). QT and JT interval at 2 minutes as well as QT and JT dispersion at 10 and 30 minutes during dofetilide infusion were significantly higher in female than in male rabbits. After 30 minutes of dofetilide infusion, 10 of 10 female rabbits had severe cardiac arrhythmias (complete AV block, PVT, or VF), so ECG parameters were impossible to assess (vs 3/10 males with severe cardiac arrhythmias; P < 0.05). During dofetilide infusion, female rabbits developed complete AV block, PVT, or VF at doses about 50% lower than those given to males.</AbstractText>The present study indicates that female rabbits are more susceptible to drug-induced long QT and cardiac arrhythmias than are male rabbits; therefore, female rabbits are more appropriate for testing drug-induced cardiac arrhythmias.</AbstractText> |
3,920 | Worldwide clinical experience with a new dual-chamber implantable cardioverter defibrillator system. | Management of atrial tachyarrhythmias represents a significant challenge in patients with implantable cardioverter defibrillators (ICDs). Drug therapy of these arrhythmias is limited by moderate efficacy, ventricular proarrhythmia, and drug-device interactions. This study tested the safety and efficacy of a new dual-chamber ICD to detect and treat atrial as well as ventricular tachyarrhythmias.</AbstractText>A dual-chamber ICD (Medtronic 7250 Jewel AF) was implanted in 293 of 303 patients at 49 centers in Europe, Canada, and North America. Specific data were collected at implant and during a mean follow-up period of 7.9+/-4.7 months. There were no clinically evident failures to detect and treat ventricular arrhythmias. In patients with at least one of the dual-chamber detection criteria activated, 1,056 of 1,192 episodes of ventricular tachycardia or fibrillation detected were judged to be appropriate (89% positive predictive accuracy). Therapy efficacy was 100% in the ventricular fibrillation zone and 98% in the ventricular tachycardia zone. Positive predictive accuracy for detection of atrial episodes was 95% (1,052/1,107). For episodes classified as atrial tachycardia by the device, the efficacy of atrial antitachycardia pacing and high-frequency (50-Hz) burst pacing was 55% and 17%, respectively. High-frequency burst pacing terminated 16.8% of episodes classified as atrial fibrillation, and atrial defibrillation had an estimated efficacy of 76%. The actuarial estimates of 6-month complication-free survival and total survival were 88% and 94%, respectively.</AbstractText>This novel dual-chamber ICD is capable of safely and effectively discriminating atrial from ventricular tachyarrhythmias and of treating atrial tachyarrhythmias without compromising detection and treatment of ventricular tachyarrhythmias.</AbstractText> |
3,921 | Cardiac arrhythmia in patients undergoing surgical repair of Ebstein's anomaly. | Arrhythmias remain an unsolved problem in Ebstein's anomaly. The aim of this study was to investigate the evolution of arrhythmias after surgical repair.</AbstractText>Forty-five patients with Ebstein's anomaly and arrhythmias were studied. Mean age was 33 +/- 15 years. Twenty-four patients (53%) had paroxysmal supraventricular tachycardia, 12 (27%) had atrial fibrillation or flutter, 8 (18%) had ventricular preexcitation (Wolff-Parkinson-White syndrome), and 1 (2%) had a nonsustained ventricular tachycardia. Surgical technique included detachment of the tricuspid anterior leaflet and suture on the atrioventricular annulus associated with right ventricular longitudinal plication.</AbstractText>There were four hospital deaths (9%). A pacemaker was implanted early after operation in 5 patients (11%). During a mean follow-up of 57 +/- 50 months (range, 4 to 226 months), there were six additional deaths, three of which were sudden. Two patients were lost to follow-up. Of the 33 surviving patients, 8 (24%) continued to have symptomatic arrhythmias, and 15 (45%) were in permanent sinus rhythm. Of the 24 patients with preoperative paroxysmal supraventricular tachycardia and the 12 with atrial fibrillation or flutter preoperatively, 9 and 2 of the survivors, respectively, have had no further episodes of arrhythmia. The incidence of arrhythmia with or without symptoms was reduced to 39% (13/33) of the surviving patients.</AbstractText>Arrhythmia is not totally abolished after operation. However, patients with Ebstein's anomaly and arrhythmia show substantial improvement after conservative surgical intervention.</AbstractText> |
3,922 | Technical aspects and outcome of in situ right internal thoracic artery grafting to the major branches of the circumflex artery via the transverse sinus. | Little is known about the anatomic limitations of in situ right internal thoracic artery (RITA) grafting to the circumflex artery.</AbstractText>To evaluate the technical aspects and outcome of revascularization of the proximal and distal major branches of the circumflex artery (obtuse marginal [OM] branch and posterolateral [PL] branch), a total of 145 patients who possessed a graftable branch of the circumflex artery were enrolled into the prospective project. There were 73 patients who had the PL branch as a primary target and 72 patients with OM branches, which were allocated by a blinded observer who reviewed the preoperative angiography.</AbstractText>Changes of primary target vessels were required in 9 patients (6.2%), yielding an overall success rate of RITA grafting of 93.8%. The success rates of RITA grafting to the OM branch and the PL branch were 95.8% (69/72; CI 88.3% to 99.1%) and 91.7% (67/73; CI 83.0% to 96.9%), respectively. The univariate analysis identified grafting under hypothermic ventricular fibrillation as predictors of inability to use in situ RITA grafting for revascularization of the circumflex artery. RITA grafting to the PL branch is not identified as a predictor. Postoperative angiography in 136 patients revealed only one occlusion (0.75%) of the RITA graft anastomosed to the marginal artery. There were no significant differences in patency rates between left and right ITA grafts.</AbstractText>This prospective study showed that in situ RITA was, in most cases, able to reach most branches of the major circumflex artery and demonstrated an excellent patency rate.</AbstractText> |
3,923 | Midterm evaluation of the Tissuemed (Aspire) porcine bioprosthesis: 493 patients, 506 bioprostheses. | Valve durability has been a major concern with bioprostheses, and the Tissuemed (Aspire) porcine bioprosthesis was designed to provide a solution to structural valve failure. Because bioprostheses tend to fail by 8 years, the aim of our study was to determine its midterm durability and performance.</AbstractText>We reviewed 506 prostheses that were implanted in 493 patients (287 men; mean age 73 +/- 6 years) between 1991 and 1999. Preoperatively 316 (68%) patients were in New York Heart Association class III or IV. There were 417 (85%) aortic, 61 (12%) mitral, 13 (2.6%) aortic and mitral, and two (0.4%) tricuspid procedures. Concomitant procedures were performed in 163 (33%) patients. Follow-up was complete in 488 (98.9%) patients with a total cumulative follow-up of 1,402 patient-years.</AbstractText>The 30-day mortality in this elderly population was 10% (95% confidence interval, 8 to 13), with no early valve-related deaths. Patients' survival at 8 years was 46% +/- 7%. This was influenced by the following factors: (1) the patient's age, being worse for those 70 years or older (p = 0.005); (2) those in New York Heart Association functional class III and IV (p = 0.004); (3) those in atrial fibrillation before the operation (p = 0.006); (4) those with poor left ventricular function (p = 0.009); and (5) those who had a previous cardiac operation (p = 0.003). Valve-related complications (expressed as percent per patient-year) were thromboembolism at 0.9%/patient-year; major hemorrhage at 1.4%/patient-year; bacterial endocarditis at 0.4%/patient-year; nonstructural dysfunction at 0.2%/patient-year, and reoperation at 0.2%/patient-year. At 8 years, freedom from thromboembolism was 93% +/- 7%, major hemorrhage, 90% +/- 4%, nonstructural dysfunction, 99% +/- 1%, structural valve failure, 100%, and reoperation, 99% +/- 1%. At follow-up, 98% of survivors were in New York Heart Association class I or II.</AbstractText>Our study suggests that at 8 years, the Tissuemed (Aspire) porcine bioprosthesis is durable and has satisfactory performance with low complication rates.</AbstractText> |
3,924 | Comparison of digoxin versus low-dose amiodarone for ventricular rate control in patients with chronic atrial fibrillation. | 1. Rapid ventricular rate (VR) and rhythm irregularity during atrial fibrillation (AF) impair cardiac performance. Although digoxin has been widely used in patients with AF, its efficacy for the control of VR and rhythm irregularity is unsatisfactory. Whether low-dose amiodarone is more effective remains unclear. 2. We randomized 16 patients (13 male, three female; mean (+/-SD) age 63 +/- 9 years) with chronic AF to receive either digoxin or amiodarone for 24 weeks. At baseline and at 12 and 24 weeks follow up, Holter monitor recording and cardiopulmonary exercise test were performed to assess VR and rhythm irregularity control and exercise capacity. 3. Seven and nine patients received digoxin and amiodarone, respectively. After 12 and 24 weeks treatment, both digoxin and amiodarone significantly decreased the mean ambulatory VR and the VR during peak exercise compared with baseline (all P < 0.05). At 24 weeks, there were no significant differences between digoxin and amiodarone in the percentage reduction in VR during ambulatory (27 +/- 13 vs. 25 +/- 12%, respectively; P = 0.8) and peak exercise (13 +/- 12 vs. 12 +/- 10%%, respectively; P = 0.6). 4. The rhythm irregularity, as measured by SD of RR intervals and the root mean square of the SD of RR intervals, and the exercise capacity, as measured by exercise workload, maximal oxygen consumption (VO2), minute ventilation, ventilatory equivalent and oxygen pulse, were not significantly changed after treatment with digoxin or amiodarone (all P > 0.05). 5. Quality of life, determined by SF-36 questionnaire, and AF symptomatology, as measured by the AF Symptom Checklist, were also not significantly changed after treatment with digoxin or amiodarone (all P > 0.05). 6. In conclusion, digoxin and low-dose amiodarone had similar efficacy in the control of VR during ambulatory activity and exercise. However, both were less efficacious during exercise and did not significantly affect rhythm irregularity, exercise capacity, quality of life and AF symptomatology in patients with chronic AF. |
3,925 | Defibrillation energy requirements and electrical heterogeneity during total body hypothermia. | Determine the effects of hypothermia on defibrillation energy requirements and cardiac electrophysiology.</AbstractText>Prospective randomized acute intervention trial.</AbstractText>Medical center animal laboratory.</AbstractText>Fifteen domestic farm swine.</AbstractText>Swine were randomized to a hypothermia group (n = 8) or a control group (n = 7). All animals were instrumented with a transvenous defibrillation system connected to a defibrillator that delivers a biphasic-truncated waveform. Values for defibrillation energy requirements were measured at baseline (normothermia, 38-40 degrees C) and during treatment with total body hypothermia (30 degrees C) or no temperature change (sham). Hypothermia was induced by circulating ice-water through anterior and posterior surgical thermal blankets.</AbstractText>Defibrillation energy requirement values at 20%, 50%, and 80% were determined by using an up/down method. In the hypothermia group, defibrillation energy requirement values at baseline did not significantly change during hypothermia (defibrillation energy requirements 50% = 14 +/- 2 J vs. 15 +/- 2 J, respectively). Similarly, the defibrillation energy requirement values in the control group did not change from baseline to sham phase (defibrillation energy requirements 50% = 12 +/- 1 J vs. 13 +/- 1 J, respectively). Hypothermia profoundly affected cardiac electrophysiology, decreasing ventricular fibrillation threshold by 72%, conduction velocity by 25% (p < .01), and tissue excitability, while it prolonged ventricular repolarization and refractoriness by 7.5% to 15%, respectively (p < .05).</AbstractText>Total body cooling to 30 degrees C was highly arrhythmogenic, although this unstable electrophysiological state did not alter ventricular defibrillation energy requirements. These data suggest that hypothermia may be used to slow metabolic processes without concern over the ability to successfully defibrillate and treat hypothermia-induced arrhythmias.</AbstractText> |
3,926 | Clinical Trials Update: CAPRICORN, COPERNICUS, MIRACLE, STAF, RITZ-2, RECOVER and RENAISSANCE and cachexia and cholesterol in heart failure. Highlights of the Scientific Sessions of the American College of Cardiology, 2001. | This is a synopsis of presentations made at the American College of Cardiology (ACC) in 2001 summarising recent research developments relating to heart failure. Clinical studies of particular interest to physicians with an interest in heart failure and its prevention are reviewed. The COPERNICUS trial lends further support to the use of the beta-blocker, carvedilol, in severe heart failure and the CAPRICORN trial to its use in patients with post-infarction left ventricular systolic dysfunction. The MIRACLE study reinforces the evidence from three smaller trials that cardiac resynchronisation therapy is an effective treatment for the relief of symptoms in patients with severe heart failure and cardiac dyssynchrony. The STAF trial casts further doubt on the wisdom of cardioversion as a routine strategy for the management of chronic atrial fibrillation. The RITZ-2 trial suggests that an intravenous, non-selective endothelin antagonist is effective in improving haemodynamics and symptoms and possibly in reducing morbidity in severe heart failure. Observational studies in heart failure suggest that a moderate excess of body fat and elevated blood cholesterol may be desirable in patients with heart failure, challenging the current non-evidenced-based vogue for cholesterol lowering therapy in heart failure. The RENAISSANCE and RECOVER outcome studies of etanercept, a tumour necrosis factor (TNF) receptor analogue that blocks the effect of TNF, were stopped because of lack of evidence of benefit shortly after the ACC. |
3,927 | Comparison of the efficacy of a subcutaneous array electrode with a subcutaneous patch electrode, a prospective randomized study. | The patch electrode and the array electrode are the two types of subcutaneous leads available as an adjunct to a transvenous lead system in patients with high defibrillation thresholds. A prospective randomized study was conducted in 30 consecutive patients comparing the efficacy and the long-term performance of a patch electrode with an array electrode. After determination of the defibrillation threshold for the transvenous lead alone, a subcutaneous patch or an array electrode was implanted in random order. Adding a patch electrode decreased the defibrillation threshold in seven out of 15 patients (47%) from 13.2+/-6.6 to 10.5+/-5.1 J (P<0.05). In 13 out of 15 patients (87%), the implantation of an array electrode caused a significant lowering of the defibrillation threshold from 15.4+/-6.6 to 8.2+/-5.0 J (P<0.0001). The array electrode was significantly more effective in lowering the defibrillation threshold than the patch electrode (P<0.01). Complications during follow-up associated with the subcutaneous patch electrode were observed in four patients whereas no complications were associated with the array electrode (P<0.01). The additional implantation of an array electrode is more effective and associated with fewer complications compared to a patch electrode. |
3,928 | Induction of atrial tachycardia and fibrillation in the mouse heart. | Atrial tachycardia and fibrillation in humans may be partly consequent to vagal stimulation. Induction of fibrillation in the small heart is considered to be impossible due to lack of a critical mass of > 100-200 mm2. Even with the recent progression of the technology of in vivo and in vitro mouse electrophysiological studies, few reports describe atrial tachycardia or fibrillation in mice. The purpose of this study was to attempt provocation of atrial tachyarrhythmia in mice using transvenous pacing following cholinergic stimulation.</AbstractText>In vivo electrophysiology studies were performed in 14 normal mice. A six-lead ECG was recorded from surface limb leads, and an octapolar electrode catheter was inserted via jugular vein cutdown approach for simultaneous atrial and ventricular endocardial recording and pacing. Atrial tachycardia and fibrillation were inducible in one mouse at baseline electrophysiology study and eleven of fourteen mice after carbamyl choline injection. The mean duration of atrial tachycardia was 126 +/- 384 s. The longest episode lasted 35 min and only terminated after atropine injection. Reinduction of atrial tachycardia after administration of atropine was not possible.</AbstractText>Despite the small mass of the normal mouse atria, sustained atrial tachycardia and fibrillation can be easily and reproducibly inducible with endocardial pacing after cholinergic agonist administration. This finding may contribute to our understanding of the classical theories of arrhythmogenesis and critical substrates necessary for sustaining microreentrant circuits. The techniques of transcatheter parasympathetic agonist-mediated atrial tachycardia induction may be valuable in further murine electrophysiological studies, especially mutant models with potential atrial arrhythmia phenotypes.</AbstractText> |
3,929 | Genetic aspects of arrhythmias. | Advances in the treatment and prevention of heart disease have led to consistently declining morbidity and mortality rates over the past 30 years. Despite these advances, therapy remains largely palliative. The development of curative therapies is limited by our lack of knowledge of the basic mechanisms of disease. In the next decade, we will probably change many of these current approaches from treating the crisis to preventing the disease. Molecular biology and genetics have elucidated several basic pathways. It is hoped that targeted therapies will prevent or arrest many of these cardiac diseases, in particular, arrhythmias and sudden death. With the discovery of the genes causing familial diseases like long QT, hypertrophic cardiomyopathy, and Brugada syndrome, we have identified several substrates responsible for triggering malignant arrhythmias. |
3,930 | The effects of endogenous and exogenous vasopressin during experimental cardiopulmonary resuscitation. | Exogenous vasopressin is a promising vasopressor when blood pressure is critically threatened, but the role of endogenous vasopressin during cardiopulmonary resuscitation (CPR) is unknown. We assessed the role of endogenous versus exogenous vasopressin in a porcine open chest CPR model. Seven minutes before induction of cardiac arrest, seven pigs received 10 microg/kg of a selective vasopressin V(1)-receptor-antagonist (Blocked Vasopressin group); another 12 pigs in two groups received saline administration only. After 4 min of untreated ventricular fibrillation followed by 3 min of basic life support CPR, six animals received 0.8 U/kg vasopressin (Exogenous Vasopressin group), whereas the blocked vasopressin group (n = 7), and the remaining six animals received saline placebo only (Endogenous Vasopressin group). Defibrillation was attempted after 14 min of CPR. During basic life support CPR, left ventricular myocardial blood flow was significantly (P < 0.05) decreased in the Blocked Vasopressin group compared with the Exogenous Vasopressin group and Endogenous Vasopressin group (42 +/- 5 compared with 64 +/- 6 and 66 +/- 6 mL x min(-1) x 100g(-1)). Left ventricular myocardial blood flow was significantly decreased in the Blocked Vasopressin group versus Exogenous Vasopressin group versus Endogenous Vasopressin group 90 s and 5 min after drug administration, respectively (38 +/- 4 and 27 +/- 3 vs 145 +/- 32 and 110 +/- 12 vs 62 +/- 4 and 56 +/- 6 mL x min(-1) x 100g(-1), respectively). None of seven Blocked Vasopressin animals, six of six Exogenous Vasopressin pigs, and six of six Endogenous Vasopressin swine had return of spontaneous circulation after 14 min of cardiac arrest including 10 min of CPR (P < 0.05). In conclusion, pigs with blocked endogenous vasopressin had poor coronary perfusion pressure and left ventricular myocardial blood flow during open chest CPR, and could not be successfully resuscitated. All pigs with effective endogenous vasopressin or pigs with effective endogenous vasopressin and additional exogenous vasopressin had good left ventricular myocardial blood flow during experimental CPR, and survived the 1-h postresuscitation phase. We conclude that endogenous vasopressin is an adjunct vasopressor to epinephrine and may serve as a back-up regulator to maintain cardiocirculatory homeostasis. |
3,931 | Atrial, ventricular, or both cannulation sites to optimize left ventricular assistance? | The efficiency of left ventricular assist devices (LVADs) depends on the capacity of the inflow cannula to drain blood into the pump. Left atrial (LA) and left ventricular (LV) sites were compared in an animal model mimicking different hemodynamic conditions. Three calves (56.3+/-5.0 kg) were equipped with a Thoratec LVAD. A regular cardiopulmonary bypass (CPB) circuit was used as a right ventricular assist device (RVAD) (jugular vein/pulmonary artery), and preload conditions were adjusted by storage (or perfusion) of blood into (or from) the venous reservoir. LA and LV drainage, tested separately or simultaneously, was measured by its effect on the LVAD's performance. The LVAD was used alone on a beating heart or together with the RVAD (biVAD) on a beating and on a fibrillating heart. Increasing the central venous pressure (CVP) highlighted the differences between the LA and LV cannulation sites when the LVAD was tested either alone or together with the RVAD (biVAD) on a beating heart. Drainage through the LA or the LV was similar when CVP was set at 8 mm Hg, and increasing CVP to 14 mm Hg allowed for better drainage through the LV cannula. In contrast, after induction of fibrillation to mimic extreme heart failure, the drainage was better through the LA cannula. Using both LA and LV cannulae simultaneously did not improve the LVAD output in any of the conditions tested. LV cannulation provides better blood drainage when used on a normal beating heart and, therefore, allows for increased LVAD performance. However, in severe heart failure, blood drainage through the LV cannula decreases and the LA cannulation site is superior. |
3,932 | [Cardiac arrhythmias in pregnancy]. | Atrial premature beats are frequently diagnosed during pregnancy (PR), supraventricular tachycardia (SVT; atrial tachycardia, AV nodal reentrant tachycardia, circus movement tachycardia) less frequently. For acute therapy, electrical cardioversion with 50-100 J is indicated in all unstable patients (pts). In stable SVT the initial therapy includes the vagal maneuver to terminate breakthrough tachycardias. For short-term management, when the vagal maneuver fails, intravenous adenosine is the first-choice drug and may safely terminate the arrhythmia. For long-term therapy, beta-blocking agents with beta 1 selectivity are first-line drugs; class Ic agents or the class III drug sotalol (sot) are effective and therapeutic alternatives. Ventricular premature beats are also frequently present during PR and benign in most pts; however, malignant ventricular tachyarrhythmias (sustained ventricular tachycardia [VT], ventricular flutter [VFlut], ventricular fibrillation [VF]) were observed less frequently. Electrical cardioversion is necessary in all pts with a hemodynamically unstable situation and life-threatening ventricular tachyarrhythmias; in hemodynamically stable pts, initial therapy with ajmaline, procainamide or lidocaine is indicated. If prophylactic therapy is needed, beta-blocking agents with beta 1 selectivity are considered as first-choice drugs. If this therapy is ineffective, class Ic agents or sot can be considered. In pts with syncopal VT, VF, VFlut or aborted sudden death an implantable cardioverter-defibrillator is indicated. In pts with symptomatic bradycardia, a pacemaker can be implanted using echocardiography at any stage of PR. The treatment of the pregnant patient with cardiac arrhythmias requires important modification of the standard practice of arrhythmia management. The goal of therapy is to protect the patient and fetus through delivery, after which chronic or definitive therapy can be administered. |
3,933 | Pupil diameter and light reaction during cardiac arrest and resuscitation. | Traditionally, both pupil diameter and reaction to light have been examined to confirm the diagnosis of death. In the present study, we investigated quantitative changes in pupil diameter and light reaction for assessing the efficacy of cardiopulmonary resuscitation (CPR) and as a predictor of outcome.</AbstractText>Controlled experimental study.</AbstractText>Animal research laboratory at a university-affiliated research institute.</AbstractText>Fifteen domestic male pigs weighing between 33 and 40 kg.</AbstractText>Ventricular fibrillation was induced with an alternating current delivered to the right ventricular endocardium. After 7 mins of untreated ventricular fibrillation, chest compression and mechanical ventilation were initiated and maintained for 6 mins. Restoration of spontaneous circulation then was attempted by electrical defibrillation.</AbstractText>Spontaneous circulation was reestablished in 9 of 15 animals. Pupils were fully dilated, and pupillary reaction to light was absent in 7 of the 9 resuscitated animals during untreated cardiac arrest. Progressive decreases in pupil diameter were observed together with restoration of light reaction during CPR, in each animal that was successfully resuscitated. When the pupils remained dilated and unreactive after 6 mins of CPR, resuscitation efforts were uniformly unsuccessful. A highly significant linear correlation between coronary perfusion pressure generated during precordial compression and pupil diameter was documented. Both were predictive of outcome.</AbstractText>Dynamic changes of pupil diameter and reactions to light during cardiac arrest and resuscitation were correlated with coronary perfusion pressure, and both predicted the likelihood that spontaneous circulation and cerebral function would be restored.</AbstractText> |
3,934 | Inhibition of nitric oxide improves coronary perfusion pressure and return of spontaneous circulation in a porcine cardiopulmonary resuscitation model. | During spontaneous circulation, nonspecific inhibition of nitric oxide synthase by N(G)-nitro-L-arginine methyl ester (L-NAME) increases systemic vascular resistance and, therefore, mean arterial pressure. If this effect can be extrapolated to cardiopulmonary resuscitation (CPR), administering L-NAME during CPR may be beneficial by maintaining or even improving coronary perfusion pressure, and hence successful defibrillation.</AbstractText>Prospective, randomized laboratory investigation using an established porcine model with instrumentation for hemodynamic variables, blood gases, and defibrillation attempt.</AbstractText>University medical center experimental laboratory.</AbstractText>Ten domestic pigs.</AbstractText>After 4 mins of ventricular fibrillation, ten animals were randomly assigned to receive L-NAME (25 mg/kg; n = 5) or saline placebo (n = 5) (given in two doses) after 3 and 13 mins of CPR, respectively. Defibrillation was provided 5 mins after the second dose of active drug or placebo.</AbstractText>Mean +/- sem coronary perfusion pressure was significantly (p < .05) higher 90 secs (27 +/- 3 vs. 17 +/- 3 mm Hg), 10 mins (28 +/- 3 vs. 14 +/- 2 mm Hg), and 15 mins (21 +/- 5 vs. 7 +/- 3 mm Hg) after the first L-NAME administration compared with saline placebo. Mean +/- sem coronary perfusion pressure remained significantly higher 90 secs and 5 mins after the second L-NAME vs. saline placebo administration (19 +/- 4 vs. 6 +/- 4 mm Hg, and 17 +/- 3 vs. 4 +/- 4 mm Hg). After 22 mins of cardiac arrest, including 18 mins of CPR, four of five pigs in the L-NAME group were successfully defibrillated, and survived the 60-min postresuscitation phase. In the placebo group, none of five pigs could be defibrillated successfully (p < .05).</AbstractText>Nonspecific blockade of nitric oxide synthase with L-NAME during CPR was associated with an increase in coronary perfusion pressure and resulted in significantly better initial resuscitation when compared with saline placebo.</AbstractText> |
3,935 | Pulmonary vein orifice isolation for eliminating paroxysmal atrial fibrillation after ICD implantation. | We treated a patient with dilated cardiomyopathy (DCM) and sustained ventricular tachycardia by an implantable cardioverter defibrillator (ICD). He then suffered from inappropriate ICD shocks triggered by paroxysmal atrial fibrillation (AF). We successfully performed pulmonary vein orifice isolation to eliminate paroxysmal AF. The pulmonary vein orifice isolation was a simple and useful procedure for eliminating paroxysmal AF in patient with decreased left ventricular (LV) function after ICD implantation. |
3,936 | S-100b, sE-selectin, and sP-selectin for evaluation of hypoxic brain damage in patients after cardiopulmonary resuscitation: pilot study. | S-100b is thought to be a screening marker of hypoxic brain damage in patients with cardiac arrest. However, the time-dependent occurrence and relevance of increased S-100b serum levels in out-of-hospital patients with cardiopulmonary resuscitation (CPR) is still discussed. The purpose of our study was to evaluate the diagnostic utility of S-100b measurements in comparison to that of adhesion molecules sE-selectin and sP-selectin in patients with CPR. Sixteen out-of-hospital patients (median age 69.6 years; range 59.2-82.2 years) suffering from cardiac arrest due to ventricular fibrillation, asystole, or electromechanical dissociation were recruited prospectively. Blood samples were drawn on scene after the return of spontaneous circulation (ROSC) and 12 hours after successful CPR. The reference group consisted of 10 patients with isolated severe head trauma (SHT) (Glasgow Coma Score </ or =8), and the control group comprised 20 healthy volunteers. Serum concentrations of S-100b, determined by immunoluminometric assay, were compared with serum levels of sE-selectin and sP-selectin measured by an enzyme-linked immunosorbent assay and correlated with the patients' survival. In the CPR group, S-100b serum levels (2.37 ng/ml; 1.37-4.09 ng/ml) at study entry (11.6 minutes after arriving on scene) did not significantly differ from those of SHT patients (2.88 ng/ml; 1.78-8.81 ng/ml). Both groups showed significant differences from the healthy controls (0.04 ng/ml; 0.01-0.82 ng/ml). At 12 hours after CPR the serum levels had decreased to 0.41 ng/ml (0.24-0.51 ng/ml) but continued to be significantly elevated compared to that of the control group. sE-selectin values in serum increased from 56.00 ng/ml (38.50-85.50 ng/ml) on scene to 79.00 ng/ml (52.00-127.00 ng/ml) after 12 hours (p < 0.05). The first measurements differed significantly from serum levels of the control group (22.50 ng/ml; 14.00-34.00 ng/ml) and from those of the SHT group (45.00 ng/ml; 39.00-63.75 ng/ml). At 12 hours after study entry the sE-selectin values were not significantly different from those of the SHT group (51.50 ng/ml; 39.00-95.88 ng/ml). sP-selectin serum levels increased slightly from 199.50 ng/ml (184.25-227.25 ng/ml) to 247.00 ng/ml (206.50-354.75 ng/ml). First and second measurements did not reveal any significant differences in either the SHT group or the healthy controls. When correlated with survival, S-100b measurements exhibited constantly high serum levels for patients, decreasing within the first 24 hours, whereas they decreased significantly in patients with longer survival. sP-selectin values on scene slightly increased in cases of survivals less than 24 hours after CPR. sE-selectin serum levels always remained within normal levels and revealed no significance later on. In contrast to the endothelium-derived adhesion molecules sE-selectin and sP-selectin, comparison of measurements of specific neuroprotein S-100b early after cardiac arrest and 12 hours later seem to provide an indication of the severity of hypoxic brain damage and the prognosis after CPR. Further investigations are required to better understand the CPR-related mechanisms of blood-brain barrier damage. |
3,937 | Impact of pulmonary valve replacement on arrhythmia propensity late after repair of tetralogy of Fallot. | Chronic pulmonary regurgitation after repair of tetralogy of Fallot (TOF) may lead to right ventricular dilatation, which may be accompanied by ventricular tachycardia and sudden death. We aimed to examine the effects of pulmonary valve replacement (PVR) on (1) certain electrocardiographic markers predictive of monomorphic ventricular arrhythmia and sudden death and (2) sustained atrial flutter/fibrillation and monomorphic ventricular tachycardia.</AbstractText>We studied 70 patients who underwent PVR for pulmonary regurgitation and/or right ventricular outflow tract obstruction late after repair of TOF. Maximum QRS duration and QT dispersion were measured from standard ECGs before PVR and at the latest follow-up. Arrhythmia was defined as sustained atrial flutter/fibrillation or sustained monomorphic ventricular tachycardia. Concomitant intraoperative electrophysiological mapping and/or cryoablation were performed in 9 patients (60%) with preexisting ventricular tachycardia and 6 patients (50%) with preexisting atrial flutter. QRS duration remained unchanged in the study group (P=0.46), but it was significantly prolonged (P<0.001) in a comparable group of patients with repaired TOF who did not undergo PVR. At a mean follow-up of 4.7 years, the incidence of ventricular tachycardia diminished from 22% to 9% (P<0.001), and atrial flutter/fibrillation decreased from 17% to 12% (P=0.32). Intraoperative ablation prevented recurrence of preexisting tachyarrhythmia (0 of 15 patients).</AbstractText>PVR in patients with previous TOF repair and chronic pulmonary regurgitation leads to stabilization of QRS duration and, in conjunction with intraoperative cryoablation, to a decrease in the incidence of preexisting atrial and ventricular tachyarrhythmia. When applicable, this combined approach should be used in patients late after repair of TOF.</AbstractText> |
3,938 | Is arrhythmia detection by automatic external defibrillator accurate for children?: sensitivity and specificity of an automatic external defibrillator algorithm in 696 pediatric arrhythmias. | Use of automatic external defibrillators (AEDs) in children aged <8 years is not recommended. The purpose of this study was to develop an ECG database of shockable and nonshockable rhythms from a broad age range of pediatric patients and to test the accuracy of the Agilent Heartstream FR2 Patient Analysis System for sensitivity and specificity.</AbstractText>Children aged </=12 years who either developed arrhythmias or were at risk for developing arrhythmias were studied. Two sources were used for the database: children whose rhythms were recorded prospectively via a modified AED and children who had arrhythmias captured on paper and digitized for subsequent analysis. The rhythms were divided into 5-second strips, classified by 3 reviewers, and then assessed by the AED analysis algorithm. A total of 696 five-second rhythm strips from 191 children (81 female and 110 male) aged 1 day to 12 years (median 3.0 years) were analyzed. There was 100% specificity for nonshockable rhythms. Sensitivity for ventricular fibrillation was 96%.</AbstractText>There was excellent AED rhythm analysis sensitivity and specificity in all age groups for ventricular fibrillation and nonshockable rhythms. The high specificity and sensitivity indicate that there is a very low risk of an inappropriate shock and that the AED correctly identifies shockable rhythms, making the algorithm both safe and effective for children.</AbstractText> |
3,939 | In vivo and in vitro acute cardiovascular effects of bimoclomol. | Effects of bimoclomol, the novel heat shock protein (HSP) coinducer, was studied in various mammalian cardiac and rabbit aortic preparations. Bimoclomol decreased the ST-segment elevation induced by coronary occlusion in anesthetized dogs (56% and 80% reduction with 1 and 5 mg/kg, respectively). In isolated working rat hearts, bimoclomol increased coronary flow (CF), decreased the reduction of cardiac output (CO) and left ventricular developed pressure (LVDP) developing after coronary occlusion, and prevented ventricular fibrillation (VF) during reperfusion. In rabbit aortic preparations, precontracted with phenylephrine, bimoclomol induced relaxation (EC(50)=214 microM). Bimoclomol produced partial relaxation against 20 mM KCl, however, bimoclomol failed to relax preparations precontracted with serotonin, PGF(2) or angiotensin II. All these effects were evident within a few minutes after application of bimoclomol. A rapid bimoclomol-induced compartmental translocation of the already preformed HSPs may explain the protective action of the compound. |
3,940 | Implantation of cardioverter defibrillators without induction of ventricular fibrillation. | The upper limit of vulnerability (ULV) is the weakest shock at which ventricular fibrillation (VF) is not induced by a T-wave shock. This study tested the hypothesis that a vulnerability safety margin based on the ULV can be used as an implantable cardioverter-defibrillator implantation criterion.</AbstractText>Implantable cardioverter-defibrillators were implanted in 80 patients if T-wave shocks did not induce VF and the baseline-rhythm R wave was >/=7 mV. The T-wave shock was 10 J in the first 45 patients (group A) and 15 J in the last 35 patients (group B). After inductionless implantations, the first VF shock was programmed to the T-wave shock plus 5 J. If T-wave shocks induced VF, the ULV was measured and the first shock was programmed to the ULV+5 J. Inductionless implantations were performed in 58 patients (72%), 28 in group A (62%) and 30 in group B (86%; P=0.04). If T-wave scanning had been done at 15 J in group A patients, inductionless implantations could have been performed in 84% of them. At 3 months, VF was induced twice during electrophysiological study in 75 patients (94%). All VFs were detected in </=4.7 s and were terminated by the first shock. During follow-up, 197 of 198 appropriate first shocks for rapid ventricular tachycardia or VF (99%) were successful in patients who had inductionless implantations (95% confidence intervals, 97% to 100%).</AbstractText>Inductionless implantations can be performed in >80% of implantable cardioverter-defibrillator recipients using a vulnerability safety margin based on a T-wave scan at 15.</AbstractText> |
3,941 | Atrial fibrillation in patients with pure isolated severe rheumatic mitral regurgitation. | This study examines the significance of the parameters that identify patients with mitral regurgitation (MR) and atrial fibrillation (AF) and discusses the indications for surgery in such patients.</AbstractText>Patients with MR and chronic AF (group I, n=64) and those without AF (group II, n=138) were studied by clinical and echocardiographic methods. Stepwise regression analysis identified factors associated with the presence of atrial fibrillation.</AbstractText>Group I patients were older and more symptomatic. They had larger left ventricular (LV) end systolic dimension (4.6+/-1.1 cm vs 3.8+/-0.8 cm, p=0.03), left atrial (LA) dimension (5.4+/-2.0 cm vs 4.1+/-1.3 cm, p=0.02), LA area (55.9+/-27.1 cm2 vs 35.9+/-17.5 cm, p=0.003) and lower LV ejection fraction (58.8+/-8.0% vs 72.4+/-7.4%, p=0.0003). Right ventricular systolic pressure was higher (57.6+/-18.1 mm Hg vs 33.6+/-12.1 mm Hg, p=0.02). By stepwise regression analysis, factors that predicted the presence of AF were age (p < 0.03) and LA dimension (p < 0.01). A higher LV end systolic dimension and lower LV ejection fraction than the recommended value for good operative outcome were present in them. Emerging indications for surgery and predictors of poor outcome were seen.</AbstractText>Atrial fibrillation in MR indicates a more chronic and severe disease process with worsening of left as well as right sided haemodynamics in spite of digoxin. Drifting towards decompensation, these patients are likely candidates for early surgery.</AbstractText> |
3,942 | Comparison of a 6-hour and 9-hour protocol for evaluation of moderate-to-low risk chest pain patients in an emergency department diagnostic unit. | To compare the 30-day outcomes of patients enrolled in a 6-hour and 9-hour emergency department (ED)-based chest pain centre (CPC) protocol.</AbstractText>All patients with the chief complaint of chest pain, who were older than 25 years, or with cocaine usage within 96 hours of initial presentation, were eligible for enrolment. Exclusion criteria included acute ST-segment elevation or depression >1 mm in 2 contiguous leads, history of coronary artery disease (CAD), haemodynamic instability or clinical syndromes consistent with unstable angina. Outcomes included ED disposition and cardiac events at 30 days (defined as acute myocardial infarction (AMI), percutaneous trans-luminal coronary angiography (PTCA), coronary artery bypass graft surgery (CABG),ventricular tachycardia or fibrillation (VT/VF) arrest, congestive heart failure (CHF) admission or cardiac-related death). The 9-hour protocol consisted of ST-segment monitoring,serial CK-MB draws at 0, 3,6 and 9 hours as well as a graded exercise test (GXT) prior to ED disposition. The 6-hour protocol eliminated the 9-hour serum marker determination, included cardiac Troponin-I (cTn-I) and allowed a GXT, 3 hours earlier. Follow-up was obtained by medical record review, phone contact, letter and also review of national and state death registries.</AbstractText>The 9-hour protocol (October 1991-December 1997) included 2,133 patients and the 6-hour protocol (January 1998- August 1998) had 184 patients enrolled. The 6-hour protocol was not different from the 9-hour one in terms of percentage admissions (9-hour: 310, 14.5%; 6-hour: 33, 17.9%; p=0.213), Coronary Care Unit admission (9-hour: 59, 2.8%; 6-hour: 5, 2.7%; p=0.303) or 30-day cardiac events (9-hour: 38, 1.9%; 6-hour: 2, 1.3%; p=0.605).</AbstractText>The 6-hour CPC strategy is an effective and safe evaluation method for patients at low to moderate risk for acute coronary syndromes.</AbstractText> |
3,943 | Echocardiographic evolution of left ventricular and left atrial thrombi in a patient with left ventricular dysfunction due to alcoholic cardiomyopathy, chronic atrial fibrillation and multiple non-fatal systemic embolisms. | The echocardiographic characteristics and evolution of multiple pedunculated left atrial and left ventricular intracavitary thrombi in a patient with alcoholic cardiomyopathy are reported. The patient had a long history of left ventricular dysfunction and atrial fibrillation but the referring physician had not prescribed anticoagulant prophylaxis. Multiple, non-fatal, systemic embolizations occurred during hospitalization and echocardiography was used to monitor the effect of the anticoagulant therapy on the remodelling and final dissolution of intracavitary thrombi. |
3,944 | Protective effect of melanocortin peptides in rat myocardial ischemia. | The influence of the melanocortin peptide ACTH-(1-24) (adrenocorticotropin) on the consequences of short-term coronary ischemia (5 min) followed by reperfusion, and the effect of the long-acting melanocortin [Nle(4),D-Phe(7)]alpha-melanocyte-stimulating hormone (NDP-MSH) on the damage induced by a permanent coronary occlusion, were investigated in anesthetized rats. Ischemia was produced by ligature of the left anterior descending coronary artery. Reperfusion-induced arrhythmias [ventricular tachycardia (VT), ventricular fibrillation (VF)] and survival rate within the 5 min following reperfusion, blood levels of free radicals detected 2 min after reperfusion by electron spin resonance spectrometry, and amount of healthy myocardial tissue, measured 72 h after permanent coronary occlusion on immunohistologically stained serial sections, were evaluated. Postischemic reperfusion induced VT in all saline-treated rats, and VF and death in a high percentage of animals (87%). In rats treated i.v. (2.5 min after coronary occlusion) with ACTH-(1-24) (0.16-0.48 mg/kg) there was a significantly dose-dependent reduction in the incidence of arrhythmias and lethality. Ischemia/reperfusion caused a large increase in free radical blood levels; treatment with ACTH-(1-24) (0.48 mg/kg i.v.) almost completely prevented this increase. In rats subjected to permanent coronary occlusion, the amount of healthy myocardial tissue was much reduced in saline-treated rats, while in rats treated s.c. with NDP-MSH (0.27 mg/kg every 12 h) it was significantly higher. The present data demonstrate, for the first time, an unforeseen property of melanocortin peptides, i.e., their ability to significantly reduce both heart ischemia/reperfusion injury and size of the ischemic area induced by permanent coronary occlusion. |
3,945 | Effects of diacetyl monoxime and cytochalasin D on ventricular fibrillation in swine right ventricles. | Whether or not the excitation-contraction (E-C) uncoupler diacetyl monoxime (DAM) and cytochalacin D (Cyto D) alter the ventricular fibrillation (VF) activation patterns is unclear. We recorded single cell action potentials and performed optical mapping in isolated perfused swine right ventricles (RV) at different concentrations of DAM and Cyto D. Increasing the concentration of DAM results in progressively shortened action potential duration (APD) measured to 90% repolarization, reduced the slope of the APD restitition curve, decreased Kolmogorov-Sinai entropy, and reduced the number of VF wave fronts. In all RVs, 15-20 mmol/l DAM converted VF to ventricular tachycardia (VT). The VF could be reinduced after the DAM was washed out. In comparison, Cyto D (10-40 micromol/l) has no effects on APD restitution curve or the dynamics of VF. The effects of DAM on VF are associated with a reduced number of wave fronts and dynamic complexities in VF. These results are compatible with the restitution hypothesis of VF and suggest that DAM may be unsuitable as an E-C uncoupler for optical mapping studies of VF in the swine RVs. |
3,946 | Role of antiarrhythmic therapy in patients at risk for sudden cardiac death: an evidence-based review. | Sudden cardiac death (SCD) accounts for more than half of all cardiac deaths occurring each year in the United States. Although it has several causes, patients at greatest risk are those with coronary artery disease and impaired left ventricular function, heart failure secondary to ischemia or idiopathic dilated cardiomyopathy, hypertrophic cardiomyopathy, documented sustained ventricular tachycardia or ventricular fibrillation, and survivors of cardiac arrest. The presence of asymptomatic ventricular arrhythmias, positive signal-averaged electrocardiogram (ECG), low heart rate variability index, or inducible ventricular tachycardia or ventricular fibrillation increases the risk. In primary prevention trials in patients with ischemic heart disease, beta-blockers reduced both total mortality and SCD, whereas class I antiarrhythmic drugs, especially class IC, increased mortality. Among class III agents, d,l-sotalol and dofetilide have a neutral effect on mortality, whereas d-sotalol increases mortality. Amiodarone has a neutral effect on total and cardiac mortality but does reduce the risk of arrhythmic death and cardiac arrest. Three primary prevention trials in patients with ischemic heart disease were conducted with implantable cardioverter-defibrillators (ICDs). Patients with low ejection fractions (EFs), asymptomatic ventricular arrhythmias, and inducible ventricular tachycardia or ventricular fibrillation had significant reductions in total, cardiac, and arrhythmic death with ICDs compared with either no drug therapy or conventional antiarrhythmic agents. The ICDs did not reduce mortality in patients with low EFs and a positive signal-averaged ECG undergoing coronary bypass graft. In those with heart failure, beta-blockers reduced total and SCD mortality, but dofetilide and amiodarone had a neutral effect on mortality. In the secondary prevention of SCD, antiarrhythmic drugs alone generally are not thought to improve survival. In three trials in patients with documented sustained ventricular tachycardia or ventricular fibrillation, or survivors of SCD, ICDs reduced cardiac and arrhythmic mortality. Total mortality, however, was significantly reduced in only one of these trials. The role of antiarrhythmic drugs in secondary prevention of SCD is limited to patients in whom ICD is inappropriate or in combination with ICD. Antiarrhythmics can be given selectively with ICDs to decrease episodes of ventricular tachycardia or fibrillation to reduce ICD discharges, to suppress episodes of nonsustained ventricular tachycardia that trigger ICD discharges, to slow the rate of ventricular tachycardia to increase hemodynamic stability, to allow effective antitachycardia pacing, or to suppress supraventricular arrhythmias. |
3,947 | Novel feedback based stimulation protocol shows hysteresis in cardiac action potential duration restitution. | Short diastolic intervals (DI) produce short action potential durations (APD) due to restitution. Slope of restitution is hypothesized to be critical in initiation of VF. Importance of restitution in mechanisms of VF is recently debated, primarily because of a lack of consistent characterization of restitution. Currently used protocols, standard and dynamic, include pacing at constant S1-S1 intervals for a number of stimuli followed by an S2 or not. In these, DI are a function of both APD (memory effect) and pacing interval (DI = pacing interval--APD). Therefore, restitution functions obtained after variable number of S1 or variable S1-S1 intervals are different. We developed a novel feedback based protocol that permits selection of DI independent of pacing interval and APD. From the instant when transmembrane voltage drops below 90% of repolarization voltage, a stimulus is delivered after predetermined DI. We used DI that oscillated between 0 and 60 msec with periods ranging from 15 sec to 500 msec to quantify effects of short and long term memory on restitution. We used a Luo-Rudy dynamic model of cellular activation. Resulting restitution functions clearly showed multi-modal behavior and hysteresis. When DI increased following a period of decreasing intervals, the APD were shorter than when DI decreased following increasing intervals. Thus, same DI produce different APDs depending on past activation history. Such variation in APD may play a role in increased incidence of VF that is reported after large oscillations in heart rate, i.e. when episodes of bradycardia follow a tachycardic episode. |
3,948 | Electrocardiographic changes following primary blast injury to the thorax. | Profound physiological changes occur following primary blast exposure but the contribution of cardiac arrhythmias is unknown. Thirteen rats, under intravenous anaesthesia, were exposed to a blast wave directed at the thorax (Group II); 10 other animals underwent abdominal blast (Group III) and nine animals acted as controls (Group I). Animals were monitored before, during and after blast exposure. Group II animals demonstrated apnoea, bradycardia and hypotension. No significant physiological changes were seen in Groups I or III. Group II displayed a variety of ECG disturbances, from ventricular extrasystoles to ventricular fibrillation. All abnormalities reverted to sinus rhythm within minutes except in fatally injured animals. These ECG changes probably result from stress wave injury. Significant disturbances might account for some fatalities following primary blast exposure and may exacerbate the triad of apnoea, bradycardia and hypotension. Such observations may have important consequences for the management of blast casualties. |
3,949 | Assessment of noninvasive markers in identifying patients at risk in the Brugada syndrome: insight into risk stratification. | The aim of this study was to compare the use of various noninvasive markers for detecting risk of life-threatening arrhythmic events in patients with Brugada syndrome.</AbstractText>The role of conduction disturbance in arrhythmogenesis of the syndrome is controversial, whereas it is well established that repolarization abnormalities are responsible for arrhythmias. The value of noninvasive markers reflecting conduction or repolarization abnormalities in identifying patients at risk for significant arrhythmias has not been shown.</AbstractText>We assessed late potentials (LP) using signal-averaged electrocardiography (ECG), microvolt T-wave alternans (TWA), and corrected QT-interval dispersion (QTD) in 44 consecutive patients who had ECGs showing a pattern of right bundle branch block and ST-segment elevation in leads V1 to V3 but structurally normal hearts. The patients were compared with 30 normal individuals.</AbstractText>Eleven patients were excluded from data analysis because of an absence of ECG manifestations of Brugada syndrome at the time of the tests. A history of life-threatening events defined as syncope and aborted sudden death was present in 19 of 33 patients (58%); in 15 of the 19 patients, stimulation induced ventricular fibrillation or polymorphic ventricular tachycardia. The LP were present in 24 of 33 patients (73%); TWA were present in 5 of 31 patients (16%); and a QTD >50 ms was present in 9 of 33 patients (27%). The incidence of LP in Brugada patients was significantly (p < 0.0001) higher than in the controls, whereas incidences of TWA and QTD were not significantly different. Multivariate logistic regression analysis revealed that the presence of LP had the most significant correlation to the occurrence of life-threatening events (p = 0.006).</AbstractText>Late potentials are a noninvasive risk stratifier in patients with Brugada syndrome. These results may support the idea that conduction disturbance per se is arrhythmogenic.</AbstractText> |
3,950 | Long-term follow-up of atrial contraction after the maze procedure in patients with mitral valve disease. | We sought to determine the effectiveness of the maze procedure for maintaining sinus rhythm and atrial contraction for a long period in patients with mitral valve disease.</AbstractText>Although the maze procedure for atrial fibrillation (AF) has been effective in restoring sinus rhythm in patients with mitral valve disease, the long-term results of this procedure have not been determined.</AbstractText>We echocardiographically studied 94 consecutive patients with mitral valve disease before, as well as early (3.1 +/- 3.3 months) and late (2.2 +/- 0.9 years) after, the maze procedure. Peak velocity and the time-velocity integral of the left ventricular (LV) diastolic filling wave during atrial contraction (A wave), as well as the atrial filling fraction (calculated as the ratio of the time-velocity integral of the A wave to total diastolic filling), were obtained from transmitral flow recordings. Peak A wave velocity > or =10 cm/s was considered to indicate echocardiographic evidence of effective atrial contraction.</AbstractText>Regular rhythm with P waves was restored in 70 patients (74%) in the early stage and in 59 patients (63%, p = 0.09) in the late stage after the maze procedure. Forty-seven patients (50%) in the early stage and 36 patients (38%, p = 0.14) in the late stage showed effective atrial contraction by Doppler echocardiography. Left atrial (LA) and LV end-diastolic diameters significantly decreased after the procedure (from 59 +/- 13 to 48 +/- 7 mm, p < 0.01; and from 54 +/- 9 to 47 +/- 5 mm, p < 0.01, respectively) and did not show significant changes during the follow-up period. Once atrial contraction was resumed, its degree did not change between the early and late stages after the maze procedure (17 +/- 6% vs. 17 +/- 6% for atrial filling fraction).</AbstractText>Sinus rhythm and atrial contraction recovered early after the maze procedure in most patients and were maintained for more than two years. Once active atrial contraction was resumed, the degree of contraction did not change thereafter. These results demonstrate that the maze procedure is effective for a long period in patients with mitral valve disease.</AbstractText> |
3,951 | Production of narrow but deep lesions suitable for ablation of atrial fibrillation using a saline-cooled narrow beam Nd:YAG laser catheter. | Lines of radiofrequency ablation for cure of atrial fibrillation are broad, and the consequent loss of atrial mass may impair atrial function and contribute to the risk of stroke. We studied whether Nd:YAG laser could produce deep but narrower lesions.</AbstractText><AbstractText Label="STUDY DESIGN/MATERIALS AND METHODS" NlmCategory="METHODS">Laser lesions were made in ventricular myocardium of nonperfused ovine hearts and at thoracotomy in dogs.</AbstractText>Lesions were well demarcated, deep, and narrow. Saline irrigation prevented crater formation for energy levels below 200 J. Lesion depth increased with increasing duration of ablation (maximum 5.3 +/- 0.8mm, P < 0.01). The depth to width ratio was >1 in all cases (maximum 2.5 +/- 1.6). The narrowest lesions were made by using high power, short duration of exposure, and intermittent delivery.</AbstractText>Irrigated Nd:YAG laser can be used to make deep narrow myocardial lesions without crater formation. Laser ablation may be more suitable than radiofrequency ablation for intraoperative or catheter-based cure of atrial fibrillation.</AbstractText> |
3,952 | Endocardial stimulation of efferent parasympathetic nerves to the atrioventricular node in humans: optimal stimulation sites and the effects of digoxin. | The purposes of this study were to identify optimal sites of stimulation of efferent parasympathetic nerve fibers to the human atrioventricular node via an endocardial catheter and to investigate the interaction between digoxin and vagal activation at the end organ.</AbstractText>The ventricular rate was measured during atrial fibrillation, prior to and during parasympathetic nerve stimulation, in 8 patients taking digoxin and in 10 controls. High frequency electrical stimuli were delivered via an hexapolar or quadripolar electrode catheter, placed at the posteroseptal right atrium near the atrioventricular node (n=18 patients) or in the coronary sinus (n=12 of 18 patients). In 4 patients, stimulation was repeated after intravenous administration of 1 to 2 mg of atropine.</AbstractText>Nerve stimulation prolonged the R-R interval in all patients. Stimulation close to the posteroseptal right atrium led to maximal atrioventricular nodal slowing. The mean R-R intervals at baseline and during parasympathetic nerve stimulation (60 mA) from the posteroseptal right atrium and the proximal coronary sinus were 581+/-79 ms, 2440+/-466, and 900+/-228 ms respectively (p=0.0001). The response to nerve stimulation was greater in patients taking digoxin than in patients not taking the drug (p=0.02). Junctional rhythm occurred during nerve stimulation in 8/8 patients taking digoxin and 0/10 not taking the drug (p=0.0001). The response to stimulation was eliminated after atropine (p=0.01).</AbstractText>Parasympathetic nerves to the atrioventricular node were stimulated from the proximal coronary sinus as well as the posteroseptal right atrium. Stimulation at the posteroseptal right atrium resulted in the greatest response, and digoxin enhanced this response. The augmented response suggests that an interaction may exist between parasympathetic stimulation and digoxin at the end organ.</AbstractText> |
3,953 | Novel methods to evaluate controlled reperfusion techniques in cardiac surgery. | This manuscript describes two novel techniques that may be useful for comparing methods to reperfuse the heart during cardiac operations. These techniques are based on measurements of intra-myocyte ion content and the analysis of reperfusion arrhythmias.</AbstractText>Myocyte ion content was measured in normal porcine hearts before and after ischemia (cardioplegic arrest, CP arrest) using atomic absorption spectroscopy. A cobalt-EDTA complex served as the extra-cellular marker. Cobalt-EDTA was infused into the aorta together with blood or cardioplegia (CP) solution. Myocardial biopsies were taken prior to CP arrest and upon successful defibrillation 5 min after initiating reperfusion. Ventricular fibrillation (VF) was recorded prior to ischemia, and then during reperfusion. VF wavefront (WF) morphology and propagation patterns were analyzed using computer algorithms. Electrophysiologic variables for measuring VF included the multiplicity index (a descriptor of VF organization), the number of WFs detected (nwaves/s) and the mean peak first derivative of electrogram voltage with respect to time (mp d V/dt).</AbstractText>Intra-cellular sodium content increased, while intra-cellular magnesium content decreased between control and reperfusion measurements (p < 0.05). Electrophysiologic recovery was characterized by increasingly rapid depolarization (i.e. more negative mp d V/dt) and an increasing nwaves/s during the first minute of post-CP reperfusion.</AbstractText>Atomic absorption spectroscopy and computer-based analysis of reperfusion VF successfully measured metabolic and electrophysiologic events that occurred during controlled reperfusion. These methods may be useful for comparing controlled reperfusion techniques.</AbstractText> |
3,954 | Effect of the atrial blanking time on the detection of atrial fibrillation in dual chamber pacing. | Patients with paroxysmal atrial fibrillation (PAF) and dual chamber pacemakers frequently have short postventricular atrial blanking times and sensitive atrial sensing thresholds used to provide reliable detection and mode switching during AF. However, short atrial blanking times increase the risk of atrial sensing of ventricular far-field signals. We evaluated if the length of the atrial blanking time influences the detection of AF. The study included ten patients with a VDDR (n = 7) or DDDR system (n = 3), who presented with AF at 18 follow-up visits. Bipolar atrial sensing was programmed to the most sensitive value. Atrial blanking times were programmed from 100 to 200 ms in 25-ms steps in each patient. Using marker annotation, the following parameters were measured at ten consecutive ventricular beats: VAF = the interval between ventricular stimulus and first sensing of AF; AFS = the number of atrial-sensed events between two ventricular events; and XAF = the interpolated number of atrial-sensed events during atrial blanking time. The intervals between ventricular events and between atrial-sensed event markers showed no significant differences for the five blanking times tested. There was no significant influence of the atrial blanking time onto the measured parameters (least square means +/- standard error) with VAF between 281 +/- 12 and 300 +/- 12 ms (P = NS), AFs between 3.4 +/- 0.2 and 3.6 +/- 0.2 beats (P = NS) and XAF between 1.84 +/- 0.12 and 2.03 +/- 0.12 beats (P = NS). At ventricular rates < 100/min, the atrial sensing of AF in dual chamber pacemakers demonstrated no evidence for deterioration by an increase of the atrial blanking time from 100 to 200 ms. Thus, the risk of ventricular far-field sensing may be reduced without compromising atrial sensing. |
3,955 | Implantation of a dual chamber pacing and sensing single pass defibrillation lead. | Dual-chamber ICDs are increasingly used to avoid inappropriate shocks due to supraventricular tachycardias. Additionally, many ICD patients will probably benefit from dual chamber pacing. The purpose of this pilot study was to evaluate the intraoperative performance and short-term follow-up of an innovative single pass right ventricular defibrillation lead capable of bipolar sensing and pacing in the right atrium and ventricle. Implantation of this single pass right ventricular defibrillation lead was successful in all 13 patients (age 63 +/- 8 years; LVEF 0.44 +/- 0.16; New York Heart Association [NYHA] 2.4 +/- 0.4, previous open heart surgery in all patients). The operation time was 79 +/- 29 minutes, the fluoroscopy time 4.7 +/- 3.1 minutes. No perioperative complications occurred. The intraoperative atrial sensing was 1.7 +/- 0.5 mV, the atrial pacing threshold product was 0.20 +/- 0.14 V/ms (range 0.03-0.50 V/ms). The defibrillation threshold was 8.8 +/- 2.7 J. At prehospital discharge and at 1-month and 3-month follow-up, atrial sensing was 1.9 +/- 0.9, 2.1 +/- 0.5, and 2.7 +/- 0.6 mV, respectively, (P = NS, P < 0.05, P < 0.05 to implant, respectively), the mean atrial threshold product 0.79, 1.65, and 1.29 V/ms, respectively. In two patients, an intermittent exit block occurred in different body postures. All spontaneous and induced ventricular arrhythmias were detected and terminated appropriately. Thus, in a highly selected patient group, atrial and ventricular sensing and pacing with a single lead is possible under consideration of an atrial pacing dysfunction in 17% of patients. |
3,956 | Physician interpretation and quantitative measures of electrocardiographic ventricular fibrillation waveform. | The characteristics of the ventricular fibrillation (VF) waveform may influence treatment decisions and the likelihood of therapeutic success. However, assessment of VF as being fine or coarse and the distinction between fine VF and asystole are largely subjective. The authors sought to determine the level of agreement among physicians for interpretation of varying VF waveforms, and to compare these subjective interpretations with quantitative measures.</AbstractText>Six-second segments of waveform from LIFEPAK 300 units were collected. Fifty segments, including 45 VF and five ventricular tachycardia (VT) distracters, were graphed to simulate rhythm strips. These waveforms were quantitatively described using scaling exponent, root-mean-squared amplitude, and centroid frequency. Thirty-two emergency medicine residents were asked to interpret the arrhythmias as VT, "coarse" VF, "fine" VF, or asystole. Their responses were compared with the qantitative measures. Interphysician agreement was assessed with the kappa statistic.</AbstractText>One thousand four hundred forty interpretations were analyzed. There was fair agreement between physicians about the classification of arrhythmias (kappa = 0.39). Mean values associated with coarse VF, fine VF, and asystole differed in all three quantitative measure categories. The decision whether to defibrillate was highly correlated with the distinction between VF and asystole (Pearson chi-square = 1,170.40, df = 1, p[two-sided] < 0.001).</AbstractText>With only fair agreement on the threshold of fine VF and asystole, defibrillation decisions are largely subjective and caregiver-specific. These data suggest that quantitative measures of the VF waveform could augment the current standard of subjective classification of VF by emergency care providers.</AbstractText> |
3,957 | Long-term results after repair of total anomalous pulmonary venous connection. | Operative strategies and early results concerning repair of Total Anomalous Pulmonary Venous Connection (TAPVC) are relatively well known. Less well defined data are available to evaluate the long-term outcome. We would therefore like to contribute our long-term data in this presentation.</AbstractText>Between 1958 and 1992 52 consecutive patients aged two days to 42 years (15 neonates, 16 infants, 9 children and 12 adults) with TAPVC were operated on. The data were collected retrospectively from the records. In 24 patients, a current follow-up study was performed, including clinical evaluation, echocardiography, and a twenty-four-hour ambulatory ECG.</AbstractText>Early mortality was 34.6% (n = 18). The postoperative follow-up period ranged from 4 months to 28 years (mean 10.7 years). There were 4 late deaths, yielding an overall long-term mortality of 7.7% (4/52). Causes of death were severe hypoplasia of central pulmonary veins in 1, ventricular fibrillation (2) and non-cardiac in one case. 80% of the operative survivors were available for assessment. Preoperatively, 11 of these patients were in NYHA functional class II, six in class III and seven in class IV. After treatment, 22 patients were in class I and two in class II. Ventricular function was evaluated by echocardiography and invasive catheterization. Only two of 24 patients (8%) showed an abnormal IVS-motion and enlargement of the right ventricle. Cardiac catheterization revealed a mean PA pressure of 26 mmHg, the peak systolic pressure in the RV was 34 mmHg. All 24 long-term survivors underwent assessment of cardiac rhythm by 24 h electrocardiogramm (ECG) monitoring. Significant arrhythmias were recorded in 11 of 24 cases (46%), including sinus node dysfunction in 3 patients. Multiform ventricular ectopic beats were evaluated in 9 cases. According to the Lown classification, 7 patients were class I while 2 cases were considered to be class IV.</AbstractText>A normal hemodynamic state can be achieved in most cases. Significant arrhythmias may exist in asymptomatic patients late after surgical correction of TAPVC, and therefore, long-term follow-up of these patients, including 24 h ECG monitoring, is recommended, even if they are asymptomatic.</AbstractText> |
3,958 | [Bouveret's tachycardia]. | In 1889, in an age preceding the invention of the electrocardiogram, a physician working in the hospitals of Lyon published a remarkable paper on essential paroxysmal tachycardia, of which Bristowe in England and Huppert in Germany had already spoken. The study described 12 cases (including 3 personal cases) of essential paroxysmal tachycardia and 6 secondary tachycardias. They were not all benign, there being 4 deaths out of the 12 cases. From this period on, the term "Bouveret's tachycardia" has been used in France and, with the advances in rhythmology, some have assimilated it to paroxysmal nodal tachycardia. In fact, many forms of paroxysmal essential tachycardia have been recognised at atrial (nodal tachycardia, accessory pathway tachycardia, idiopathic atrial flutter and fibrillation) and ventricular levels (benign or ventricular Bouveret's tachycardia). This is an occasion to review the variety of clinical medicine in the accuracy of a rhythmological diagnosis without forgetting that the electrocardiogram is essential when the recordings are analysable. The term of Bouveret's tachycardia should be retained but, before electrocardiographic analysis, it englobes all paroxysmal tachycardia occurring in healthy hearts, and not only paroxysmal nodal tachycardia. |
3,959 | [Arrhythmic cardiomyopathy]. | Arrhythmic cardiomyopathy (ACM) is a clinical entity which can be reproduced in experimental models and which corresponds to all myocardial changes induced by chronic tachycardia. It may affect the atria and/or ventricles and, in this case, occur with all types of arrhythmia. Arrhythmia complicating a cardiomyopathy is the differential diagnosis of ventricular ACM. Nevertheless, the potential deleterious haemodynamic changes of any chronic arrhythmia may aggravate pre-existing ventricular dysfunction and, therefore, should always be considered. The development of ACM is usually progressive and depends on the heart rate, but there may also be a myocardial predisposition in certain cases. ACM is an association of haemodynamic, electrophysiological, metabolic and histological changes. Regression, which is the rule, starts in the first days following control of the ventricular rhythm but continues clinically over several months. The physiopathological mechanisms of ACM are multiple and include essentially abnormal cellular calcium concentrations. The treatment is optimally the restoration and maintenance of sinus rhythm, or at least control of the ventricular rate. Because of its curative effects, selective radiofrequency ablation of the arrhythmogenic substrate is the treatment of choice when this is localised. In chronic atrial fibrillation, when sinus rhythm cannot be maintained, the control of the ventricular response at rest and on exercise depends on pharmacological treatment, and, when ineffective, on radiofrequency modification of atrioventricular conduction with optimisation of the pacing mode. |
3,960 | [Right ventricular dilatation and intraventricular septal motion after surgical closure of atrial septal defect]. | The persistence of right ventricular dilatation and paradoxical interventricular septal motion are two echocardiographic abnormalities rarely reported after surgical closure of atrial septal defects. The aim of this study was to identify the predictive factors of these abnormalities in the long-term and to study their functional consequences. One hundred and two patients aged 18 +/- 14 years (range 1-62 years) underwent closure of atrial septal defects. Thirty-five patients were under 10 years of age, 33 were 10 to 20 years of age and 34 were over 20. Fifty-six patients were female. The rhythm was sinus in the great majority of cases (97%). Three patients, all over 40 years of age, were in atrial fibrillation. Before surgery, right ventricular dilatation was observed in 95 patients (91.2%), paradoxical septal wall motion in 93 patients (91.2%), the ratio of pulmonary/systemic output was 2.7 +/- 0.6 (range 1.7 to 7.4) and over 2 in 90% of patients: pulmonary systolic pressure was 32.3 +/- 12 mmHg and over 40 mmHg in 18 patients (17.6%). Ninety-four patients were followed up regularly with a mean follow-up time of 5.5 +/- 3.6 years (1-14 years). The right ventricle remained dilated in 37 patients (39.4%) after surgery: the right ventricular dimension decreased from 36 +/- 1 to 27.8 +/- 6.2 mm (p = 0.001). The ratio of end diastolic right ventricular/left ventricular dimension also decreased from 1.07 +/- 0.31 to 0.56 +/- 0.12 (p = 0.0001). Multivariate analysis identified two predictive factors of persistent right ventricular dilatation: age > 40 years (p = 0.009) and a pulmonary/systemic flow ratio > 3 (p = 0.03). Interventricular septal wall motion remained paradoxical in 21 patients (22%). Multivariate analysis identified two predictive factors of persistent paradoxical septal motion: age > 40 years (p = 0.02) and systolic pulmonary pressures > 40 mmHg (p = 0.03). These abnormalities remained asymptomatic in all but two patients with persistent long-term hypertension and a residual atrial septal defect. The persistence of right ventricular dilatation and paradoxical septal motion was quite common, with older age at surgery, systolic pulmonary artery pressure > 40 mmHg and a ratio of pulmonary/systemic blood flow > 3, being predisposing factors. These abnormalities were clinically asymptomatic when isolated. |
3,961 | [Cardiovascular manifestations of hyperthyroidism. Clinical significance and preoperative preparation]. | More than 200 years ago, Caleb Parry described cardiological manifestations of hyperthyroidism. Interaction of thyroid hormones and sympathoadrenal system (responsible for rhythm disorders) and direct effect of thyroid hormones on the cardiac muscle (responsible for occurrence of hypertrophy and cardiac insufficiency) have been recognized as the pathophysiological basis of cardiovascular disorders of patients with hyperthyroidism. The aim of the study was to retrospectively analyze surgically treated patients with different types of hyperthyreosis, and establish the incidence and clinical significance of the left ventricular dysfunction related to duration and treatment of hyperthyreosis. Evaluation of left ventricular function was based on the ejection fraction during exercise. Signs of hypertrophy were echocardiographically, radiographically and electrocardiographicaly recorded. Over the period 1993-1997 at the Surgical Department of the institute of Endocrinology in Belgrade 423 patients with hyperthyreosis were operated: 293 (69.26%) patients had Graves-Basedow's disease, 74 (17.49%) toxic adenoma, and 58 (13.28%) toxic polynodal struma. The average duration of the disease in patients with Graves-Basedow's hyperthyreosis was 5 yrs, and the average age of patients was 29 yrs; the average duration of hyperthyreosis in patients with toxic adenoma was 1.2 yrs, and in cases of toxic polynodal struma 17 yrs. Pathological response of ejection fraction during exercise was recorded in 60% of patients. Signs of hypertrophy of the left chamber were recorded in 17% of subjects, and insufficiency of the left chamber with congestive stasis in the lungs in 4.6% of patients. The most common ECG changes were: synus tachycardia, higher voltage of P and T waves, elevated amplitude of QRS complex, prolonged P-Q and shortened Q-T intervals. In 20% of cases atrial fibrillation was evidenced. One patient had ECG signs of myocardial infarction. Clinical features of left ventricular dysfunction in hyperthyroidism include: occurrence in younger patients with history of hyperthyroidism, progressive course and occurrence of congestive cardiac failure as well as reversible nature of all cardiac changes after radical therapy of hyperthyreosis which can be medical, surgical or irradiation. |
3,962 | Congenital long QT syndromes and Brugada syndrome: the arrhythmogenic ion channel disorders. | Congenital long QT syndromes (LQTS) and Brugada syndrome are hereditary disorders of cardiac ion channels which result in life-threatening cardiac arrhythmias or sudden cardiac death in patients with anatomically normal hearts. The pathogenesis of these dramatic events has been partially elucidated with the identification of the individual ion channels involved and understanding of the effect of some disease-causing mutations on the membrane currents and action potential. The clinical spectrum of congenital LQTS is broader than previously thought and involves certain patients previously diagnosed with idiosyncratic drug-induced proarrhythmia. The initial treatment for congenital LQTS patients involves beta-blockers in most cases. Indications for implantable cardioverter-defibrillator (ICD) or pace-maker (PM) implantation in selected individuals continue to evolve. |
3,963 | Sympathetic nerve sprouting, electrical remodeling and the mechanisms of sudden cardiac death. | The purpose of this article is to review the nerve sprouting hypothesis of sudden cardiac death. It is known that sympathetic stimulation is important in the generation of sudden cardiac death. For example, there is a diurnal variation of sudden death rate in patients with myocardial infarction. Beta blockers, or drugs with beta blocking effects, are known to prevent sudden cardiac death. It was unclear if the cardiac nerves in the heart play only a passive role in the mechanisms of sudden death. To determine if nerve sprouting and neural remodeling occur after myocardial infarction, we performed immunocytochemical studies of cardiac nerves in explanted native hearts of transplant recipients. We found that there was a positive correlation between nerve density and a clinical history of ventricular arrhythmia. Encouraged by these results, we performed a study in dogs to determine whether or not nerve growth factor (NGF) infusion to the left stellate ganglion can facilitate the development of ventricular tachycardia (VT), ventricular fibrillation (VF), and sudden cardiac death (SCD). The results showed that augmented myocardial sympathetic nerve sprouting through NGF infusion plus atrioventricular (AV) block and MI result in a 44% incidence (four of nine dogs) of SCD and a high incidence of VT in the chronic phase of MI. In contrast, none of the six dogs (with AV block and MI) without NGF infusion died suddenly or had frequent VT episodes. Based on these findings, we propose the nerve sprouting hypothesis of ventricular arrhythmia and SCD. The hypothesis states that MI results in nerve injury, followed by sympathetic nerve sprouting and regional (heterogeneous) myocardial hyperinnervation. The coupling between augmented sympathetic nerve sprouting with electrically remodeled myocardium results in VT, VF and SCD. Modification of nerve sprouting after MI may provide a novel opportunity for arrhythmia control. |
3,964 | Late ventricular arrhythmias during acute regional ischemia in the isolated blood perfused pig heart. Role of electrical cellular coupling. | Acute ischemia comes with two phases of life-threatening arrhythmias, early (within 10 minutes, 1A) and late (after about 15 minutes, 1B). The mechanism of the latter is unknown and in this paper, we test the hypothesis that a phase of intermediate coupling between surviving epicardium and inexcitable midmyocardium underlies 1B arrhythmias.</AbstractText>Pig hearts (n=26) were retrogradely perfused with a blood Tyrode's mixture. The left anterior descending artery was occluded. We investigated (1) inducibility of ventricular fibrillation (VF) with programmed stimulation, (2) tissue impedance (Rt) heterogeneity within the ischemic zone, (3) multiple subepicardial and midmyocardial electrograms, (4) subepicardial lactate dehydrogenase (LDH) and glycogen content.</AbstractText>In nine of ten hearts, one--three premature stimuli caused VF between 14 and 53 min of ischemia. This typically happened when the Rt of the ischemic zone had increased up to 40% of its final value. More uncoupling terminated the period of VF inducibility. The excitability of the surviving subepicardial layer was depressed during the same period with partial uncoupling, but recovered when the uncoupling from the midmyocardium had progressed further.</AbstractText>We show that 1B-VF can be induced within a distinct time window and coincides with a distinct range of Rt rise. Subepicardium is electrically depressed, presumably through coupling with midmyocardium, complete uncoupling causes subepicardial recovery and terminates the substrate for 1B-VF. Hence, we suggest that the substrate for 1B-VF consists of intermediate coupling of subepicardium and midmyocardium.</AbstractText> |
3,965 | Cellular mechanism of reentry induced by a strong electrical stimulus: implications for fibrillation and defibrillation. | The objective of this review article is to describe the graded response hypothesis of reentry induced by a strong single electrical stimulus in the normal canine ventricular myocardium. It is shown that the graded responses (subthreshold depolarization during phase 3 of the action potential) induced at a site distant (S2) from the regular S1--S1 pacing site, propagate slowly over short distances (approximately 5 mm) and initiate a regenerative action potentials in recovered cells near the S1 site. Activation wave then blocks near the S2 site (unidirectional block) but reenters when the S2 site recovers it excitability. Super strong S2 currents do not induce reentry (upper limit of vulnerability). Since similar activation sequence and properties are shown to exist in intact canine hearts during induction of ventricular fibrillation with a similar S2 stimulus, the graded response hypothesis may have relevance to vulnerability to fibrillation. Furthermore, since the upper limit of vulnerability is closely related to defibrillation threshold, the graded response hypothesis might also be relevant to defibrillation mechanism. Other proposed mechanisms of fibrillation and defibrillation (critical point hypothesis, the progressive depolarization hypothesis and the hypothesis of phase singularity of defibrillation failure) are also discussed in this review paper and compared to the graded response hypothesis. |
3,966 | Mechanisms underlying ventricular tachycardia and its transition to ventricular fibrillation in the structurally normal heart. | Reentrant ventricular tachycardia (VT) is the most common sustained arrhythmia leading to ventricular fibrillation (VF). However, despite more than a century of research, the mechanism(s) of the conversion from reentrant VT to VF have not been elucidated. Based on their different electrocardiographic appearance, reentrant VT and VF have traditionally been thought of as resulting from two widely different mechanisms. Whereas VT is seen as a rapid but well organized process whereby the excitation wave rotates about a single well-defined circuit, fibrillation has been described as turbulent cardiac electrical activity, resulting from the random and aperiodic propagation of multiple independent wavelets throughout the cardiac muscle. Recently, the application of concepts derived from the theory of non-linear dynamics to the problem of wave propagation in the heart and the advent of modern high-resolution mapping techniques, have led some investigators to view VT and VF in terms of a single mechanism, whereby the self-organization of electrical waves forms 'rotors' that give rise to rapidly rotating spiral waves and results in either VT or VF, depending on the frequency of rotation and on the interaction of wave fronts with the cardiac muscle. As such, monomorphic VT is thought to result from a stationary rotor, whose frequency of rotation is within a range that allows 1:1 excitation of both ventricles. On the other hand, VF is thought to result from either a single rapidly drifting rotor, or a stationary rotor whose frequency of excitation is exceedingly high, thus resulting in multiple areas of intermittent block and giving rise to complex patterns of propagation with both deterministic and stochastic components. This article reviews the prevailing theories for the maintenance of VF, and discusses recently proposed mechanisms underlying transitions between VT and VF. |
3,967 | Concealed arrhythmogenic syndromes: the hidden substrate of idiopathic ventricular fibrillation? | In approximately 6--10% of survivors of cardiac arrest no cardiac abnormality can be identified despite extensive clinical evaluation. Autopsy data confirm that in a similar percentage of victims of sudden death no structural heart disease can be identified at post mortem evaluation. Occurrence of cardiac arrest in the absence of a substrate is defined 'idiopathic ventricular fibrillation' thus admitting that the cause for the arrhythmic event has remained unknown. We present data supporting the hypothesis that incompletely penetrant genetic defects may underlie at least some of these unexplained deaths. |
3,968 | Differences in the pharmacodynamics of epinephrine and vasopressin during and after experimental cardiopulmonary resuscitation. | Vasopressin has been investigated as a possible alternative to epinephrine during cardiopulmonary resuscitation (CPR). We tested the hypothesis that vasopressin, in comparison with epinephrine, would improve cerebral blood flow and metabolism during CPR as well as after restoration of spontaneous circulation (ROSC). A total of 22 anaesthetised piglets were subjected to 5 min of ventricular fibrillation followed by 8 min of closed-chest CPR. The piglets were randomly allocated to receive repeated boluses of either 45 microg/kg epinephrine or 0.4 U/kg vasopressin IV. Haemodynamic parameters, cerebral cortical blood flow and cerebral tissue pH and PCO(2) were continuously monitored during CPR and up to 4 h after ROSC. Cerebral oxygen extraction ratio was calculated. Cerebral cortical blood flow increased transiently after each bolus of epinephrine, while only the first bolus of vasopressin resulted in a sustained increase. The peak in cerebral cortical blood flow was reached approximately 30 s later with vasopressin. During the initial 5 min following ROSC, cerebral cortical blood flow was greater in the vasopressin group. In conclusion, there is a difference between epinephrine and vasopressin in the time from injection to maximal clinical response and the duration of their effect, but their overall effects on blood pressures and cerebral perfusion do not differ significantly during CPR. In contrast, vasopressin results in a greater cerebral cortical blood flow during a transient period after ROSC. |
3,969 | Is there a difference between women and men in characteristics and outcome after in hospital cardiac arrest? | To describe the characteristics and outcome among patients suffering from an in-hospital cardiac arrest in women and men.</AbstractText>All patients who suffered an in-hospital cardiac arrest during a 4 year period in Sahlgrenska Hospital Göteborg, Sweden, where the cardiopulmonary resuscitation (CPR) team was called, were recorded and described prospectively in terms of characteristics and outcome.</AbstractText>There were 557 patients suffering in-hospital cardiac arrest in whom the CPR-team was alerted. Among them, 217 (39%) were women. Women differed from men having a lower prevalence of earlier myocardial infarction, angina pectoris, renal disease and a higher prevalence of rheumatic disease. In terms of aetiology of the cardiac arrest, 47% men and 48% women were judged to have had a confirmed or possible AMI. More men than women were found in ventricular fibrillation/ventricular tachycardia (VF/VT) (57 vs. 41%; P<0.001), whereas more women were found in pulseless electrical activity (30 vs. 15%; P<0.0001). Cerebral performance categories (CPC)-score at discharge did not differ between men and women. Among women, 36.4% survived to discharge as compared with 38.0% among men (NS). Survival from VF/VT was 64.3% in women and 52.7% in men (NS). When correcting for dissimilarities at baseline, the adjusted odd ratio for being discharged alive from hospital among women as compared with men was 1.66 (95% confidence limit 1.06-2.62; P=0.028).</AbstractText>Thirty nine percent of patients suffering in-hospital cardiac arrest for whom the CPR-team was alerted, were women. Women were less frequently found in VF/VT than men. After correcting for dissimilarities at baseline, female gender was associated with a small improvement in survival.</AbstractText> |
3,970 | Patient outcomes following defibrillation with a low energy biphasic truncated exponential waveform in out-of-hospital cardiac arrest. | To determine the outcome of patients with out-of-hospital cardiac arrest and ventricular fibrillation as the presenting rhythm while using automated external defibrillators (AEDs) that delivered non-escalating, impedance-compensated low-energy (150 J) shocks.</AbstractText>AEDs delivering low-energy biphasic truncated exponential (BTE) shocks were employed in an emergency medical services (EMS) system in which first-arriving personnel - police, firefighters or paramedics - delivered the initial shocks. Patients were classified according to their response to shocks: restoration of sustained spontaneous circulation (ROSC) without need for epinephrine and other advanced life support (ALS) interventions; and ALS, those requiring epinephrine in all instances. The primary end-point was neurologically-intact discharge survival. Secondary end-points were ROSC with shocks only and the call-to-shock time interval.</AbstractText>Of 42 patients with VF arrest treated with BTE shocks, 35 were bystander-witnessed. Of these 35, 14 (38%) regained a sustained ROSC on-scene with shocks only, needing no epinephrine for ROSC. All 14 survived to discharge home. Of the remaining 21 patients needing ALS intervention, only two (9.5%) survived to discharge. Overall, 16/35 patients (46%) survived to discharge home, an outcome comparable to our experience with patients treated with escalating high-energy monophasic waveform shocks.</AbstractText>Low-energy (150 J) non-escalating biphasic truncated exponential waveform shocks terminate VF in out-of-hospital cardiac arrest with high efficacy; patient outcome is comparable with that observed with escalating high-energy monophasic shocks. Low-energy shocks, in addition to high efficacy, may confer the advantage of less shock-induced myocardial dysfunction, though this will be difficult to define in the clinical circumstance of long-duration VF provoked by a pre-existing diseased myocardial substrate.</AbstractText> |
3,971 | An evaluation of the impact of gender and age on QT dispersion in healthy subjects. | To determine if gender, age, and gender per age category, have an impact on QT and QTc dispersion in healthy volunteers.</AbstractText>This study was undertaken in 150 patients (50 per age group, 75 males, 75 females). The age groups included young (20-40 years), middle-aged (41-69 years) and elderly (> 70 years) subjects. The QT intervals on a 12 lead ECG were determined and Bazett's formula was used to derive the QTc intervals. The QT and QTc dispersion were determined by subtracting the shortest QTc interval from the longest on each 12-lead recording.</AbstractText>Males had higher QT dispersion than females (50 +/- 22 vs 42 +/- 18 ms, P = 0.017) but QTc dispersion was not significantly changed. No significant differences were seen among the different age categories for QT or QTc dispersion. In elderly subjects, males had higher QT and QTc dispersion than females (54 +/- 23 vs 42 +/-15 ms, P = 0.039 and 63 +/- 23.7 vs 48 +/- 21 ms, P = 0.032, respectively).</AbstractText>When evaluating the effect of gender in different age categories, elderly males have significantly greater QT and QTc dispersion than elderly female subjects. No other gender differences were noted for QT or QTc dispersion in the other two age categories. When evaluating a population of healthy volunteers, regardless of age, gender has an impact on QT dispersion but no significant interaction with QTc dispersion. Evaluating age without dividing the data by gender yields no significant differences in QT or QTc dispersion.</AbstractText> |
3,972 | Variability in the manifestation of pre-excited atrial fibrillation: its quantification, theoretical origin, and diagnostic potential. | Irregular broad complex tachycardia (BCT) may be due to atrial fibrillation (AF) occurring in the presence of ventricular pre-excitation (pre-excited AF) or bundle branch block (BBB-AF). While irregularity is a defining characteristic of AF, it is a common subjective impression that greater variability in manifestation exists for pre-excited AF than BBB-AF. This difference can potentially be exploited for distinguishing the two conditions if some means can be found to quantify it.</AbstractText>For each of 75 ECGs showing irregular BCT (41 pre-excited AF and 34 BBB-AF), a random sample of 10 distinct QRS complexes were selected for quantitative measurement of variability in manifestation, which included the standard deviation (SD) of the width, the SD of the axis, and the coefficient of variation (CV) of the amplitude of the QRS complex.</AbstractText>Pre-excited AF showed statistically significantly greater values than BBB-AF with respect to these measures, and receiver-operating characteristic curves showed that these differences could be useful for their discrimination. For the SD of QRS width, a cut-off value of 8 ms appeared optimal (sensitivity 1.00 and specificity 0.79). For the SD of QRS axis, a cut-off value of 2.5 degrees appeared optimal (sensitivity 0.84 and specificity 0.56). For the CV of QRS amplitude, a cut-off value of 0.10 appeared optimal (sensitivity 0.82 and specificity 0.76).</AbstractText>Pre-excited AF demonstrated greater variability than BBB-AF in manifestation. The measures of variability developed can potentially be useful for diagnosing irregular BCT in practice, especially in the context of automated computer-aided diagnosis.</AbstractText> |
3,973 | External cardioversion of atrial fibrillation: comparison of biphasic vs monophasic waveform shocks. | It is well established in transthoracic ventricular defibrillation that biphasic truncated waveform shocks are associated with superior defibrillation efficacy when compared with damped sine wave monophasic waveform shocks. The aim of this study was to explore whether biphasic waveform shocks were superior to monophasic waveform shocks for external cardioversion of atrial fibrillation (AF).</AbstractText>Fifty-seven patients in whom cardioversion of AF was indicated were randomized in this prospective study, to transthoracic cardioversion with either monophasic damped sine waveform shocks or biphasic impedance compensating waveform shocks. In the group randomized to monophasic waveform shocks (27 patients), a first shock of 150 J was delivered, followed (if necessary) by a 360 J shock. In the biphasic waveform group (30 patients), the first shock had an energy of 150 J and (if necessary) a second 150 J was delivered. All shocks were delivered in the anterolateral chest pad position. Sinus rhythm was restored in 16 patients (51%) with the first monophasic shock and in 27 patients (86%) with the first biphasic shock. The difference was statistically significant (P=0.02). After the second shock, sinus rhythm was obtained in a total of 24 patients (88%) with monophasic shocks and in 28 patients (93%) with biphasic shocks. No complication was observed in either group and cardiac enzymes (CK, CKmb, troponin I, myoglobin) did not show any significant changes.</AbstractText>This study suggests that at the same energy level of 150 J, biphasic impedance compensating waveform shocks are superior to monophasic damped sine waveform shocks cardioversion of atrial fibrillation.</AbstractText> |
3,974 | Low-energy internal cardioversion in patients with long-lasting atrial fibrillation refractory to external electrical cardioversion: results and long-term follow-up. | Low-energy internal cardioversion is a new electrical treatment for patients with persistent atrial fibrillation. This paper evaluates the efficacy and safety of low-energy internal cardioversion in patients with long-lasting atrial fibrillation refractory to external electrical cardioversion, and the clinical outcome of such patients.</AbstractText>The study population consisted of 55 patients [32 male, mean age 65 +/- 10 years, 48 (87%) with underlying heart disease] with long-lasting (mean 18 +/- 34 months) atrial fibrillation in whom external cardioversion had failed to restore sinus rhythm. Two custom-made catheters were used: one positioned in the right atrium and one in the coronary sinus or the left pulmonary artery. A standard catheter was inserted into the right ventricular apex to provide R wave synchronization. Sinus rhythm was restored in 52 patients (95%) with a mean defibrillating energy of 6.9 +/- 2.6 J (320 +/- 60 V). No complications were observed. During follow-up (mean 18 +/- 9 months), 16 patients (31%) suffered early recurrence (< or = 1 week) of atrial fibrillation and 20 patients (38%) had late recurrence (> 1 week, mean 3.5 +/- 3.6 months) of atrial fibrillation. Six patients with a late recurrence again underwent cardioversion and five of these maintained sinus rhythm. Therefore, a total of 21/52 patients (40%) were in sinus rhythm at the end of follow-up. No clinical difference was found between patients with and without recurrences.</AbstractText>Low-energy internal cardioversion is a useful means of restoring sinus rhythm in patients with long-lasting atrial fibrillation refractory to external electrical cardioversion. More than one-third of patients maintained sinus rhythm during long-term follow-up.</AbstractText> |
3,975 | Syncope in pharmacologically unmasked Brugada syndrome: indication for an implantable defibrillator or an unresolved dilemma? | A 30-year-old Caucasian male was referred for evaluation of a 2-year history of recurrent post-exertion lightheadedness and near syncopal spells in the setting of a family history of unexplained sudden cardiac death. Cardiac evaluation demonstrated normal heart structure, but the 12-lead surface ECG was suggestive of but not diagnostic of Brugada syndrome. An exercise stress test reproduced the patient's usual symptoms during the recovery period, and was consistent with a typical vasovagal faint. The same symptoms were observed during a head-up tilt table test. However, given the family history and ECG, pharmacological testing with procainamide, isoprenaline and metoprolol, as well as programmed ventricular stimulation, were undertaken. Pharmacological provocation further supported a diagnosis of Brugada syndrome, whereas programmed ventricular stimulation was considered non-diagnostic regarding ventricular tachyarrhythmia susceptibility. Consequently, despite ECG and pharmacological findings suggestive of Brugada syndrome, there appeared to be sufficient evidence to believe that this patient's symptoms were the result of neurally mediated syncope and not due to ventricular tachyarrhythmias. The patient was treated with midodrine, and has remained symptom-free for 16 months. Thus, given the frequency with which vasovagal syncope occurs in young patients, its occurrence is not unexpected in individuals with concomitant diagnoses such as Brugada syndrome. In as much as current recommendations favour implantable defibrillators in symptomatic Brugada syndrome, the identification of other causes of syncope in such patients poses an uncomfortable, and currently unsettled dilemma. |
3,976 | Indications for dual-chamber cardioverter defibrillators at implant and at 1 year follow-up: a retrospective analysis in the single-chamber defibrillator era. | This retrospective four-centre study assessed the current indications for dual-chamber implantable cardioverter defibrillators (ICDs) at implant and during a medium-term follow-up period in a group of patients treated by single-chamber ICD in the pre dual-chamber ICD era.</AbstractText>The study population consisted of 153 consecutive patients (127 males, mean age 58 +/- 6 years) treated by single-chamber ICD for ventricular tachycardia and/or ventricular fibrillation. Definite indications for having a dual-chamber ICD included the presence of sinus node dysfunction and of second- or third-degree atrioventricular (AV) block, while possible indications were represented by paroxysmal atrial fibrillation or flutter and first-degree AV block. At implant, dual-chamber ICD would appear definitely indicated in 10.5% of cases, and possibly indicated in an additional 17.5% of cases. During 12 +/- 10 months follow-up, such percentages remained stable (11 and 19.5%, respectively). Inappropriate ICD intervention was documented in five of 13 patients (38%), with episodes of paroxysmal atrial fibrillation or flutter.</AbstractText>In this non-selected study population, a dual-chamber ICD would have potentially benefited approximately 30% of the patients. During medium-term follow-up, there was no progression towards increasing dual-chamber ICD indications. The 15% cumulative incidence of paroxysmal atrial tachyarrhythmias justifies the activation of dedicated detection algorithms.</AbstractText> |
3,977 | Intravenous administration of class I antiarrhythmic drugs induced T wave alternans in a patient with Brugada syndrome. | A 71-year-old man who experienced aborted sudden death was referred to our hospital. Coronary artery disease and cerebral accident were ruled out by conventional tests. The 12-lead ECG obtained at rest showed a right bundle branch block pattern and ST segment elevation in leads V1 to V3. Double ventricular extrastimuli at coupling intervals >180 msec induced ventricular fibrillation (VF) twice during electrophysiologic study. Intravenous administration of procainamide accentuated ST segment elevation in leads V1 to V3, and visible T wave alternans was induced in leads V2 and V3 at a dose of 450 mg. Initiation of T wave alternans was not associated with changes of the cardiac cycle or development of premature beats. When procainamide infusion was discontinued, T wave alternans disappeared before the elevated ST segment returned to the control level. Pilsicainide also accentuated ST segment elevation and induced similar T wave alternans in leads V2 and V3. Class I antiarrhythmic drug-related T wave alternans has been reported rarely in Brugada syndrome, but it may represent enhanced arrhythmogenicity of VF. We need to monitor closely and study the clinical implications of T wave alternans in Brugada syndrome. |
3,978 | Reduction in atrial defibrillation threshold by a single linear ablation lesion. | This study investigated a hybrid approach to reduce the atrial defibrillation threshold (ADFT) by determining the effect of a single linear radiofrequency ablation (RFA) lesion on both the ADFT and activation patterns during atrial fibrillation (AF).</AbstractText>In 18 open chest sheep (45 to 57 kg), coil defibrillation electrodes were placed in a superior vena cava/right ventricular configuration. AF was induced by burst pacing and maintained with acetyl beta-methylcholine (2 to 42 microL/min). ADFTs were obtained before and after a linear RFA lesion was created in the left atrium (LAL; n = 6), right atrium (RAL; n = 6), or neither atrium as a control (n = 6). In animals receiving an LAL, a 504-unipolar-electrode plaque was sutured to the LA. For animals receiving an RAL, two 504-electrode plaques were placed, one each on the LA and RA. From each plaque, activations were recorded before and after ADFT shocks, and organizational characteristics of activations were analyzed using algorithms that track individual wavefronts. In sham-treated controls, the ADFT did not change. In contrast, LAL reduced ADFT energy 29%, from 4.5 +/- 2.3 J to 3.2 +/- 2.0 J (P < 0.05). RAL reduced ADFT energy 25%, from 2.0 +/- 0.9 J to 1.5 +/- 0.7 J (P < 0.05). AF activation was substantially more organized after RFA than before RFA for both the RAL- and LAL-treated animals.</AbstractText>A single RFA lesion in either the RA or LA reduces the ADFT in this sheep model. This decrease is associated with an increase in fibrillatory organization.</AbstractText> |
3,979 | Ventricular fibrillation sensing and detection by implantable defibrillators: is one better than the others? A prospective, comparative study. | We prospectively compared the performance of the sensing and detection systems of three leading defibrillator manufacturers: Medtronic, Guidant, and Ventritex.</AbstractText>Ventricular fibrillation signal was digitally recorded during defibrillator implantation and subsequently played back sequentially to a Medtronic Micro Jewel II 7223Cx, a Guidant MINI II 1762, and a Ventritex Cadet V-115C. The devices were programmed for single-zone detection, at nominal settings. Rate cutoff was set at 320 msec (185/min for the MINI). We analyzed 253 episodes from 47 patients. Median undersensing was 0%, 2.1%, and 5.3% for the Jewel, MINI, and Cadet, respectively (P < 0.001 for each paired comparison). Detection time was 4.1 +/- 1.6 seconds, 3.4 +/- 1.6 seconds, and 4.3 +/- 2.2 seconds for the Jewel, MINI, and Cadet, respectively (P < 0.001 between MINI-Jewel and MINI-Cadet; P < 0.01 between Jewel-Cadet). Delayed detection (detection time longer than the mean of all observations + 2 SD) occurred in 3 (1.2%), 7 (2.8%), and 18 (7.1%) episodes for the Jewel, MINI, and Cadet, respectively. Performance for all devices was worse when the short-separation integrated bipolar lead was used and when the episode followed a failed high-energy shock.</AbstractText>Statistically significant differences were seen in sensing and detection performance among the devices and device/lead combinations during ventricular fibrillation. These differences are related to specific features of the respective devices and should be taken into account during clinical practice, as well as in future device development.</AbstractText> |
3,980 | Catheter cryoablation of the atrioventricular node in patients with atrial fibrillation: a novel technology for ablation of cardiac arrhythmias. | Recent animal studies demonstrated the feasibility and safety of applying percutaneous catheter cryoablation technology for ablation of arrhythmogenic sites. The studies also showed that reversible "ice mapping" can be performed before creating permanent lesions. We investigated the feasibility and safety of applying this new technology in man.</AbstractText>Cryoablation of the AV node (AVN) using a 9-French quadripolar catheter with a 4-mm electrode tip was attempted in 12 patients (mean age 67.8 +/- 11.4 years) with refractory atrial fibrillation. Whereas technical issues prevented adequate tissue contact in two patients, complete AVN block was obtained in the remaining 10 patients after 4.8 +/- 1.9 cryoapplications lasting 5.5 +/- 0.2 minutes resulting in temperatures of -58.1 degrees +/- 5.4 degrees C. In all patients with sinus rhythm at the time of the procedure, cryomapping at warmer temperatures induced reversible AVN block and allowed confirmation of a successful site before definitive ablation. Intracardiac echocardiography was performed in three patients and allowed visualization of the cryocatheter-endocardial contact and cryolesion formation. No major procedural complications were reported. After 6 months of follow-up, 8 of 10 initially successful patients remained in complete block; 1 had partial recovery of AVN conduction manifested by atrial fibrillation with a slow ventricular response, and 1 fully recovered AVN conduction.</AbstractText>(1) Catheter cryoablation of the AVN can be performed safely in man. (2) Reversible cryomapping is feasible and may offer an advantage over radiofrequency ablation. (3) Cryocatheter-endocardial contact and cryolesion growth can be monitored with intracardiac echocardiography.</AbstractText> |
3,981 | Wolff-Parkinson-White syndrome mimicking acute anterior myocardial infarction in a young male patient--a case report. | A young male with Wolff-Parkinson-White syndrome whose electrocardiographic pattern was suggestive of acute anterior myocardial infarction is described. A 21-year-old male with a history of ventricular fibrillation after being successfully resuscitated was admitted to the coronary care unit. His electrocardiogram showed ST elevation in the precordial leads (V1-V6). This condition was erroneously interpreted as an acute myocardial infarction. At the fourth day, while ST elevations returned to baseline, short PR interval and delta waves were observed on the ECG. Myocardial infarction was excluded by biochemical tests, echocardiography, and coronary angiography. Electrophysiologic study confirmed Wolff-Parkinson-White syndrome with two accessory pathways. |
3,982 | [Hibernation--nature's model of resistance to ventricular fibrillation]. | During hibernation, animals lower their body temperature to a few degrees above 0 degree C. This means that when entering and emerging from hibernation their body temperature passes through the critical level of +20 degrees C, a temperature region at which non-hibernating mammals develop circulatory arrest, usually due to ventricular fibrillation (VF). The hibernator heart is resistant to VF, not only that caused by hypothermia, but also VF as induced by local application of aconitine on the epicardium, and also by other factors which ordinarily cause VF in non-hibernators. Several mechanisms may explain the resistance to VF observed in the hibernator heart. The factors of greatest importance seem to be contrasting patterns of adrenergic innervation, divergent physico-chemical properties with a lower solidification point of lipids in the hibernator, distinct enzyme temperature activity curves seen in the hibernator, and differences in the handling of intracellular calcium, resulting in protection against calcium overload in the hibernator heart as compared with the non-hibernator heart. |
3,983 | [Silent myocardial ischemia and exercise-induced arrhythmia detected by the exercise test in the total health promotion plan (THP)]. | We investigated the prevalence and characteristics of ischemic heart disease especially silent myocardial ischemia (SMI) and arrhythmia in need of careful observation in the exercise stress tests in the Total Health Promotion Plan (THP), which was conducted between 1994-96 for the purpose of measuring cardiopulmonary function. All workers (n = 4,918, 4,426 males) aged 18-60 yr old in an occupational field were studied. Exercise tests with an ergometer were performed by the LOPS protocol, in which the maximal workload was set up as a presumed 70-80% maximal oxygen intake, or STEP (original multistage protocol). ECG changes were evaluated with a CC5 lead. Two hundred and fifteen people refused the study because of a common cold, lumbago and so on. Of 4,703 subjects, 17 with abnormal rest ECG and 19 with probable anginal pain were excluded from the exercise tests. Of 4,667 who underwent the exercise test, 37 (0.79%) had ischemic ECG change, and 155 (3.32%) had striking arrhythmia. These 228 subjects then did a treadmill exercise test with Bruce protocol. Twenty-two (0.47% of 4,703) showed positive ECG change, 9 (0.19%) of 22 had abnormal findings on a 201Tl scan. 8 (0.17%) were diagnosed as SMI (Cohn I), in which the prevalence of hypertension, hyperlipidemia, diabetes mellitus, smoker and positive familial history of ischemic heart disease was greater than that of all subjects. In a 15-30 month follow up, none has developed cardiac accidents. Exercise-induced arrhythmia was detected in 11 (0.23%) subjects. Four were non-sustained ventricular tachycardia without any organic disease, 4 were ventricular arrhythmia based on cardiomyopathy detected by echocardiography, 2 were atrial fibrillation and another was WPW syndrome. It is therefore likely that the ergometer exercise test in THP was effective in preventing sudden death caused by ischemic heart disease or striking arrhythmia. |
3,984 | Effects of rhythm regularization and rate control in improving left ventricular function in atrial fibrillation patients undergoing atrioventricular nodal ablation. | To assess the relative contributions of rate control and rhythm regularization to left ventricular function in atrial fibrillation (AF) patients undergoing atrioventricular nodal ablation. This was performed by assessing the effect of ventricular rhythm regularization on left ventricular function during AF, and the effect of varying heart rate on left ventricular function after ablation.</AbstractText>Eleven patients with continuous AF and V/VI-R pacemakers undergoing therapeutic atrioventricular nodal ablation were studied. Preablation patients underwent two 30 min observation periods in a randomized, blinded fashion during which they were either in baseline AF (pacer set to default V/VI 50/min) or being paced using a rhythm stabilizing algorithm (RSA) designed to regularize rhythm without changing baseline ventricular rate. Six weeks after ablation, patients were again observed during the two following 30 min periods: pacing at a low clinically indicated rate (69+/-9 beats/min), and pacing at the rapid, mean preablation rate. During all observation periods, left ventricular function was measured continuously using a nuclear vest that provided validated measures of heart rate, ejection fraction, and normalized end-systolic volume (ESV) and end-diastolic (EDV) volume.</AbstractText>Before ablation, RSA successfully regularized rhythm, decreasing the coefficient of variation of interbeat intervals 20+/-5% to 10+/-4% (P<0.001). The heart rate with RSA (105+/-19 beats/min) was not significantly different from the baseline AF rate (102+/-21 beats/min). Increased rhythm regularity achieved by RSA significantly improved left ventricular function, decreasing ESV from 62+/-12 units to 57+/-11 units (P=0.03), and increasing the ejection fraction from 31+/-11% to 36+/-11% (P=0.03). After ablation, at the clinically indicated low pacing rate of 69+/-9 beats/min, a much greater improvement in ejection fraction was observed, increasing to 44+/-13% (P=0.005 compared with preablation). However, rapid regular pacing at the mean preablation rate of 110+/-18 beats/min eradicated this improvement, decreasing the ejection fraction to 31+/-8% (P=0.003), and increasing ESV from 53+/-13 units to 62+/-8 units (P=0.006).</AbstractText>Rhythm regularity achieved by a regularizing pacing algorithm can significantly, albeit modestly, improve left ventricular function in AF. However, more marked improvements in left ventricular function seen after ablation are primarily due to rate reduction alone.</AbstractText> |
3,985 | Defibrillation via the elimination of spiral turbulence in a model for ventricular fibrillation. | Ventricular fibrillation, the major reason behind sudden cardiac death, is turbulent cardiac electrical activity in which rapid, irregular disturbances in the spatiotemporal electrical activation of the heart make it incapable of any concerted pumping action. Methods of controlling ventricular fibrillation include electrical defibrillation as well as injected medication. Electrical defibrillation, though widely used, involves subjecting the whole heart to massive, and often counterproductive, electrical shocks. We propose a defibrillation method that uses a very low-amplitude shock (of order mV) applied for a brief duration (of order 100 ms) and over a coarse mesh of lines on our model ventricle. |
3,986 | NHE1-inhibitor cariporide prevents the transient reperfusion-induced shortening of the monophasic action potential after coronary ischemia in pigs. | During myocardial ischemia intracellular acid load increases as a consequence of anaerobic metabolism. Exchange of excessive protons for sodium via the sodium proton exchanger type 1 (NHE1) is supposed to cause intracellular sodium accumulation. The NHE1 inhibitor cariporide has been shown to inhibit ischemia and reperfusion-induced ventricular fibrillation (VF) but the mechanisms are not fully understood. During early reperfusion transient shortening of the action potential has been reported, which renders the heart susceptible to reentrant arrhythmias. In anesthetized pigs subjected to 10 min of left circumflex coronary artery (LCX) occlusion and reperfusion we have investigated whether NHE1 is involved in reperfusion-induced shortening of the monophasic action potential (MAP) taken with an epicardial probe over the ischemic area. In control pigs (n = 7) a moderate decrease in the duration of the MAP at 50 % repolarization (MAPD50) occurred during ischemia reaching 78.8 +/- 5.0% of the pre-ischemic duration at 5 min (p < 0.01) and 87.3 +/- 7.6 % after 10 min. An additional, transient but marked shortening occurred during the first 2 min of reperfusion, which fully recovered after 4 min. At 50 sec of reperfusion MAPD50 fell to 53.1 +/- 8.2 % of the pre-ischemic value corresponding to 90.1 +/- 20.2 msec of reperfusion-induced shortening. Cariporide, 3 mg/kg i.v. 5 min before occlusion (n = 6), totally prevented reperfusion-induced MAP shortening while having no effect on MAPD50 during ischemia. In conclusion, our data suggest that the immediate, transient, but strong action potential shortening during early reperfusion after 10 min of coronary ischemia is due to the activity of the NHE1. |
3,987 | Ventricular arrhythmias following coronary artery occlusion in rats: is the diabetic heart less or more sensitive to ischaemia? | Rhythm disorders are common complications in diabetic patients, due to their enhanced sensitivity to ischaemia. However, experimental studies are inconsistent, and both higher and lower vulnerability to injury has been reported. Our objectives were to compare susceptibility to ventricular arrhythmias in rats with prolonged duration of diabetes induced by streptozotocin (45 mg/kg, i.v.), utilising two different models. Following 8 weeks, either anaesthetised open-chest rats in vivo or isolated Langendorff-perfused hearts were subjected to 30 min regional zero-flow ischaemia induced by occlusion of LAD coronary artery. In addition, cardiac glycogenolysis and lactate production were measured. In open-chest rats, 90 % of the controls exhibited ventricular tachycardia (VT) which represented 55.4 % of total arrhythmias, whereby only 19.9 % of arrhythmias occurred as VT in 44 % of the diabetic rats (P < 0.05 vs controls). Duration of VT and ventricular fibrillation (VF) was reduced from 35.5 +/- 11.1 and 224.8 +/- 153.9 s in the controls to 4.8 +/- 2.5 and 2.2 +/- 0.2 s in the diabetics, respectively (P < 0.05). Accordingly, severity of arrhythmias (arrhythmia score, AS) was also lower in the diabetics (2.0 +/- 0.38 vs 3.3 +/- 0.3 in the controls; P < 0.05). In the isolated hearts, high incidence of VF was decreased in the diabetic hearts, and although VT occurred in almost all of the diabetic hearts, the duration of VT and VF was substantially shorter (61.5 +/- 14.5 and 5.5 +/- 0.5 s vs 221.5 +/- 37 and 398.5 +/- 55 s in the controls, respectively; P < 0.05). AS was reduced to 2.9 +/- 0.12 from 4.1 +/- 0.3 in the controls (P < 0.05). Postischaemic accumulation of lactate was lower in the diabetic than in the non-diabetic myocardium (20.4 +/- 1.9 vs 29.5 +/- 2.9 micromol/l/g w.wt.; P < 0.05). These results suggest that rat hearts with chronic diabetes, despite some differences in the arrhythmia profiles between the in vivo model and isolated heart preparation, are less sensitive to ischaemic injury and exhibit lower susceptibility to ventricular arrhythmias and reduced accumulation ofglycolytic metabolites. |
3,988 | Factors associated with sudden death of individuals requiring restraint for excited delirium. | The purpose of this article is to identify and rank factors associated with sudden death of individuals requiring restraint for excited delirium. Eighteen cases of such deaths witnessed by emergency medical service (EMS) personnel are reported. The 18 cases reported were restrained with the wrists and ankles bound and attached behind the back. This restraint technique was also used for all 196 surviving excited delirium victims encountered during the study period. Unique to these data is a description of the initial cardiopulmonary arrest rhythm in 72% of the sudden death cases. Associated with all sudden death cases was struggle by the victim with forced restraint and cessation of struggling with labored or agonal breathing immediately before cardiopulmonary arrest. Also associated was stimulant drug use (78%), chronic disease (56%), and obesity (56%). The primary cardiac arrest rhythm of ventricular tachycardia was found in 1 of 13 victims with confirmed initial cardiac rhythms, with none found in ventricular fibrillation. Our findings indicate that unexpected sudden death when excited delirium victims are restrained in the out-of-hospital setting is not infrequent and can be associated with multiple predictable but usually uncontrollable factors. |
3,989 | Dynamics of intramural and transmural reentry during ventricular fibrillation in isolated swine ventricles. | The intramural dynamics of ventricular fibrillation (VF) remain poorly understood. Recent investigations have suggested that stable intramural reentry may underlie the mechanisms of VF. We performed optical mapping studies of VF in isolated swine right ventricles (RVs) and left ventricles (LVs). Nine RV walls were cut obliquely in their distal edge exposing the transmural surface. Six LV wedge preparations were also studied. Results showed that intramural reentry was present. In RV, 28 of 44 VF episodes showed reentry; 15% of the activation pathways were reentrant. Except for 4 episodes, reentry was transmural, involving subendocardial structures as the papillary muscle (PM) or trabeculae. In LV, reentry was observed in 27 of 27 VF episodes; 23% of the activations were part of reentrant pathways (P<0.05 compared with RV). All LV reentrant pathways were truly intramural (confined to the wall) and were frequently located at the PM insertion. In both ventricles, reentry was spatially and temporally unstable. Histological studies showed abrupt changes in fiber orientation at sites of reentry and wave splitting. Connexin 40 immunostaining demonstrated intramyocardial Purkinje fibers at sites of reentry in the PM root and around endocardial trabeculae. Our results confirm that reentry is frequent-but unstable-in the myocardial wall during VF. In RV, reentry is mostly transmural and requires participation of subendocardial structures. The LV has a greater incidence of reentry and is intramural. Anisotropic anatomic structures played key roles in the generation of wave splitting and in the maintenance of reentry. |
3,990 | Effects of cavotricuspid isthmus catheter ablation on paroxysmal atrial fibrillation. | It has been demonstrated that successful cavotricuspid isthmus ablation of typical atrial flutter combined with atrial fibrillation (AF) sometimes influences the preablation history of paroxysmal AF. However, the effectiveness of only isthmus ablation on AF itself is unclear. Endocardial catheter mapping during induced AF was performed around the tricuspid annulus using duodecapolar clectrode catheters in 39 patients with drug-refractory paroxysmal AF. Isthmus ablation was performed in 16 patients (41%) in whom catheter mapping during AF showed an organized activation pattern around the tricuspid annulus. During a mean follow-up of 12.3 months, isthmus ablation was successful in preventing AF in 12 (75%) patients, 8 without medication and 4 with a previously ineffective drug. This success group had a significantly higher F wave amplitude in lead V1 (0.29+/-0.10 vs 0. 15+/-0.04 mV, p < 0.01), a higher left ventricular ejection fraction (74+/-9 vs 58+/-2%, p < 0.05), and a smaller left atrial dimension (35+/-6 vs 43+/-4 mm, p < 0.05) than the failure group. Isthmus ablation may be effective in preventing paroxysmal AF with an organized activation pattern around the tricuspid annulus. F wave amplitude, left ventricular ejection fraction, and left atrial dimension were significant predictors of success. |
3,991 | Use of automated external defibrillators in a Brazilian airline. A 1-year experience. | After the incorporation of automated external defibrillators by other airlines and the support of the Brazilian Society of Cardiology, Varig Airlines began the onboard defibrillation program with the initial purpose of equipping wide-body aircrafts frequently used in international flights and that airplanes use in the Rio - São Paulo route. With all flight attendants trained, the automated external defibrillation devices were incorporated to 34 airplanes of a total fleet of 80 aircrafts. The devices were installed in the baggage compartments secured with velcro straps and 2 pairs of electrodes, one or which pre-connected to the device to minimize application time. Later, a portable monitor was address to the resuscitation kit in the long flights. The expansion of the knowledge of the basic life support fundamentors and the corrected implantation of the survival chain and of the automated external defibrillators will increase the extense of recovery of cardiorespiratory arrest victims in aircrafts. |
3,992 | The old but reliable digitalis: persistent concerns and expanded indications. | Digitalis has been an old but reliable drug for 240 years. Concerns regarding its clinical indications and benefits still exist in the absence of a reduction in all-cause mortality. While intravenous digitalis is used without question in cases of atrial fibrillation, it is still controversial in sinus rhythm, despite the Digitalis Investigation Group (DIG) study showing a significant reduction in death and the need for hospitalisation for congestive heart failure in both diastolic and systolic dysfunction. The influence of digitalis in acute myocardial infarction, coronary artery disease and sudden cardiac death remains speculative. In cases of uncomplicated hypertension, it appears to prevent the onset of left ventricular dysfunction and myocardial infarction. Thus, digitalis can be a cost-effective agent with added benefits. |
3,993 | Factors modifying the effect of bystander cardiopulmonary resuscitation on survival in out-of-hospital cardiac arrest patients in Sweden. | To describe possible factors modifying the effect of bystander cardiopulmonary resuscitation on survival among patients suffering an out-of-hospital cardiac arrest.</AbstractText>A national survey in Sweden among patients suffering out-of-hospital cardiac arrest and in whom resuscitative efforts were attempted. Sixty per cent of ambulance organizations were included.</AbstractText>Prospective evaluation. Survival was defined as survival 1 month after cardiac arrest.</AbstractText>In all, 14065 reports were included in the evaluation. Of these, resuscitation efforts were attempted in 10966 cases, of which 1089 were witnessed by ambulance crews. The report deals with the remaining 9877 patients, of whom bystander cardiopulmonary resuscitation was attempted in 36%. Survival to 1 month was 8.2% among patients who received bystander cardiopulmonary resuscitation vs 2.5% among patients who did not receive it (odds ratio 3.5, 95% confidence interval 2.9-4.3). The effect of bystander cardiopulmonary resuscitation on survival was related to: (1) the interval between collapse and the start of bystander cardiopulmonary resuscitation (effect more marked in patients who experienced a short delay); (2) the quality of bystander cardiopulmonary resuscitation (effect more marked if both chest compressions and ventilation were performed than if either of them was performed alone); (3) the category of bystander (effect more marked if bystander cardiopulmonary resuscitation was performed by a non-layperson); (4) interval between collapse and arrival of the ambulance (effect more marked if this interval was prolonged); (5) age (effect more marked in bystander cardiopulmonary resuscitation among the elderly); and (6) the location of the arrest (effect more marked if the arrest took place outside the home).</AbstractText>The effect of bystander cardiopulmonary resuscitation on survival after an out-of-hospital cardiac arrest can be modified by various factors. Factors that were associated with the effect of bystander cardiopulmonary resuscitation were the interval between the collapse and the start of bystander cardiopulmonary resuscitation, the quality of bystander cardiopulmonary resuscitation, whether or not the bystander was a layperson, the interval between collapse and the arrival of the ambulance, age and the place of arrest.</AbstractText> |
3,994 | QT and JT dispersion in patients with monomorphic or polymorphic ventricular tachycardia/ventricular fibrillation. | The present study evaluates the repolarization abnormalities in patients with monomorphic sustained ventricular tachycardia (MVT) and polymorphic ventricular tachycardia/ventricular fibrillation (PMVT/VF) by measuring QT and JT dispersion on the surface electrocardiogram (ECG). QT dispersion is a predictor of ventricular arrhythmias in several clinical settings. However, the value of QT and JT dispersion in identifying patients at risk for PMVT/VF is controversial. Maximum QT (JT) interval duration and QT (JT) dispersion were compared between 20 healthy individuals, 12 patients with inducible MVT during programmed electrical stimulation and seven patients with PMVT/VF recorded during 24-hour ambulatory ECG or induced by programmed electrical stimulation. QT dispersion was 40 +/- 9 ms in the control group, 63 +/- 21 ms in the MVT group, and 79 +/- 31 ms in the PMVT/VF group. QT dispersion in both the MVT and PMVT/VF groups were significantly greater than in the control group (P <.001 and P <.0001, respectively); however, there was no significant difference between the MVT and PMVT/VF groups. JT dispersion was 41 +/- 14 ms in the control group, 69 +/- 14 ms in the MVT group and 103 +/- 37 ms in the PMVT/VF group. JT dispersion differed significantly between the study groups and was significantly increased in PMVT/VF group than in the control group or MVT groups (P <.0001 vs. the control group, P <.005 vs. the MVT group). Patients with PMVT/VF have a greater dispersion of ventricular repolarization time. Repolarization abnormalities are important for ventricular arrhythmogenesis and detectable on the surface ECG. |
3,995 | Electrical storm presages nonsudden death: the antiarrhythmics versus implantable defibrillators (AVID) trial. | Electrical storm, multiple temporally related episodes of ventricular tachycardia (VT) or ventricular fibrillation (VF), is a frequent problem among recipients of implantable cardioverter defibrillators (ICDs). However, insufficient data exist regarding its prognostic significance.</AbstractText>This analysis includes 457 patients who received an ICD in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial and who were followed for 31 +/- 13 months. Electrical storm was defined as > or = 3 separate episodes of VT/VF within 24 hours. Characteristics and survival of patients surviving electrical storm (n = 90), those with VT/VF unrelated to electrical storm (n = 184), and the remaining patients (n = 183) were compared. The 3 groups differed in terms of ejection fraction, index arrhythmia, revascularization status, and baseline medication use. Survival was evaluated using time-dependent Cox modeling. Electrical storm occurred 9.2 +/- 11.5 months after ICD implantation, and most episodes (86%) were due to VT. Electrical storm was a significant risk factor for subsequent death, independent of ejection fraction and other prognostic variables (relative risk [RR], 2.4; 95% confidence interval [CI], 1.3 to 4.2; P = 0.003), but VT/VF unrelated to electrical storm was not (RR, 1.0; 95% CI, 0.6 to 1.7; P = 0.9). The risk of death was greatest 3 months after electrical storm (RR, 5.4; 95% Cl, 2.4 to 12.3; P = 0.0001) and diminished beyond this time (RR, 1.9; 95% CI, 1.0 to 3.6; P=0.04).</AbstractText>Electrical storm is an important, independent marker for subsequent death among ICD recipients, particularly in the first 3 months after its occurrence. However, the development of VT/VF unrelated to electrical storm does not seem to be associated with an increased risk of subsequent death.</AbstractText> |
3,996 | Multicenter prospective nonrandomized study of long-term antiarrhythmic drug therapy in patients with tachyarrhythmias: Japanese Antiarrhythmics Long-Term Study-2 (JALT-2 Study). | Based on the results of the Cardiac Arrhythmia Suppression Trial (CAST), strategies for the treatment of tachyarrhythmias have changed rapidly. The Japanese Antiarrhythmics Long-Term (JALT) study was planned to investigate the present methods for choosing antiarrhythmic drugs, and the effects on long-term prognosis in patients with tachyarrhythmias in Japan. Following a 6-month preliminary study (JALT-1), there was a multicenter nonrandomized prospective study (JALT-2), with a 2-year follow-up, of patients with paroxysmal atrial fibrillation (PAF), sustained ventricular tachycardia (SVT) and nonsustained VT (NSVT). Four hundred fifty-five patients were registered, and 361 of them (79%) were analyzed. Cerebral infarction occurred in 10 of 193 patients (5.2%) with PAF. Transition to chronic AF was observed in 21 patients (10.9%), but in none of the patients receiving Ca antagonist therapy. Twenty-five patients died: 5 deaths were arrhythmic, 10 were because of pump failure, and 9 were noncardiac. The most significant difference in drug selection between JALT-1 and JALT-2 was the increase in the use of slow kinetic Na channel blockers for PAF and the decrease in the use of the same agents for VT in the JALT-2 study. A marked change of therapeutic strategy occurred in JALT-2 compared with JALT-1. Most patients with a poor prognosis had underlying heart diseases and heart failure, but the per annum rate of death by arrhythmia and pump failure in JALT-2 was less than that in JALT-1. |
3,997 | Effect of low-intensity warfarin therapy on left atrial thrombus resolution in patients with nonvalvular atrial fibrillation: a transesophageal echocardiographic study. | The presence of left atrial thrombus (LAT) is associated with an increased risk of embolic stroke. However, it has yet to be established definitively whether low-intensity warfarin therapy (INR: 1.5-2.0) can prevent LAT formation in patients with nonvalvular atrial fibrillation (NVAF). The present study analyzed the clinical and transesophageal echocardiography (TEE) features of 123 such patients to identify risk factors for LAT formation and the efficacy of prophylactic low-intensity warfarin therapy. Left atrial thrombi were found in 35 patients (28%) in whom systemic hypertension (49% vs 23%; p<0.01) and ischemic heart disease (17% vs 3%; p<0.01) were more frequent. Left ventricular ejection fraction (54+/-14% vs 60+/-11%; p<0.05), left ventricular end-diastolic dimension (51+/-7 mm vs 48+/-5 mm; p<0.05), spontaneous echo contrast (2.2+/-0.7 vs 1.4+/-0.9; p<0.01), left atrial diameter (50+/-6 mm vs 43+/-7 mm; p<0.01), left atrial appendage blood velocity (22.3+/-8.7 cm/s vs 37.2+/-21.5 cm/s; p<0.01) and the incidence of left ventricular hypertrophy (37% vs 15%; p<0.01) were also significantly different between the groups. Fourteen patients received continuous warfarin therapy (target INR: 1.5-2.0) and on the follow-up TEE study the left atrial thrombus resolved in 10 (71%). There were no thromboembolic events or major hemorrhagic complications in these patients, so it was concluded that low-intensity warfarin therapy is efficacious in treating LAT formation in patients with NVAF. |
3,998 | Safety and effectiveness of ibutilide in a community hospital. | To determine the safety and effectiveness of ibutilide, we conducted a retrospective study of patients in a community hospital from December 1997-January 2000, reviewing hospital and pharmacy records for 12 inpatients (aged 68+/-13 yrs) receiving ibutilide for atrial fibrillation or flutter. The cumulative conversion rate with ibutilide 0.012+/-0.004 mg/kg was 58%. Serious cardiovascular adverse events were documented in six patients; of those patients, five had baseline QTc intervals above 440 msec, two experienced ventricular fibrillation, and four experienced symptomatic bradycardia (range 49-60 beats/minute) requiring medical intervention. The effectiveness of ibutilide was similar to that found in previous studies. However, more complications were seen in this setting where ibutilide was used infrequently and without stringent patient selection criteria or standardized administration protocols. To ensure optimal patient care, institutions should consider implementing guidelines or education strategies to reduce the potential for serious adverse effects associated with improper screening, dosing, and monitoring of patients receiving ibutilide. |
3,999 | AV block and changes in pacing mode during long-term follow-up of 399 consecutive patients with sick sinus syndrome treated with an AAI/AAIR pacemaker. | This retrospective study included a large cohort of consecutive patients primarily implanted at Skejby University Hospital with an AAI/AAIR pacemaker because of sick sinus syndrome (SSS) from July 1981 to July 1999. The primary aim of the study was to analyze the risk of developing AV block during long-term follow-up. A secondary aim was to study the incidence and reasons for changes in pacing mode caused by other than AV block. A total of 399 patients (231 women, mean age 71 +/- 13.5 years) were identified. Mean follow-up was 4.6 +/- 3.4 years and occurred at death, reoperation with mode change, pacemaker explant, or end of study. During follow-up, 44 patients had a ventricular lead implanted with a mean delay of 2.8 +/- 3.1 years (range 1 day-10.4 years) after the primary implantation. A total of 30 patients received a ventricular lead because of AV block or AF with bradycardia (annual incidence 1.7%). Another 14 patients received a ventricular lead without having documented AV block or AF with pauses (annual incidence 0.8%). The present observational study documents that in patients with SSS treated with AAI/AAIR pacing, AV block requiring implantation of a ventricular lead occurs at a rate of 1.7% per year. It is considered that AAI/AAIR pacing is safe and reliable as treatment for patients with SSS and normal AV conduction. |
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