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4,000 | Risk factors associated with new onset tachyarrhythmias after cardiac surgery--a retrospective analysis. | Tachyarrhythmias (TA) represent a frequent and serious problem after cardiac surgery. We retrospectively analyzed 987 cardiac surgery patients admitted to a surgical intensive care unit between 1996 and 1999 to assess incidence and risk factors associated with development of postoperative TA in the intensive care unit.</AbstractText>TA (n=149) were defined as non-sinus rhythm with a heart rate (HR) > or =100 bpm in patients with preoperative sinus rhythm or as heart rate > or =130 bpm in patients with preoperative atrial fibrillation. A total of 787 patients served as controls (C). Demographic, premorbidity and perioperative data, admission SAPS and MODS-score, presence of clinical syndromes systemic inflammatory response syndrome (SIRS) and sepsis were univariately compared between groups. For prediction of independent risk factors for TA-development two multiple logistic regression models were finally established.</AbstractText>Concerning TA, atrial fibrillation and flutter (76%) were observed most frequently, followed by paroxysmal supraventricular tachycardia (15%) and ventricular tachycardia/fibrillation (11%). Age, a history or presence of congestive heart failure, development of SIRS and sepsis, severity of multiple organ dysfunction syndrome and in particular severity of cardiovascular failure proved to be independent risk factors for development of TA.</AbstractText>In cardiac surgery patients, age, a history or presence of congestive heart failure, postoperative development of a systemic inflammatory response syndrome or sepsis and the severity of multiple organ function syndrome were independent predictors for development of TA in the intensive care unit. The association of severity of cardiovascular dysfunction with TA strongly suggests a causal relationship between catecholamine therapy and TA-development.</AbstractText> |
4,001 | Spiral waves in excitable media with negative restitution. | We study numerically the dynamics of spiral waves in an excitable medium with negative restitution. For our study we use two models of the excitable medium: a cellular automaton and a reaction-diffusion model. There are no significant effects of negative restitution as long as the slope of the restitution curve is less steep than -1. In media with slopes steeper than -1, the dynamics of spiral waves can change significantly: (1) the average restitution time jumps to a value where the slope of the restitution curve is about -1; (2) spiral waves can break up into turbulent patterns. We discuss a possible connection between such instabilities and fibrillation in atrial tissue. |
4,002 | Implantation of cardioverter device in young children: the perirenal approach. | Placement of Implantable cardioverter devices in young children is complicated because of the relatively large size and heavy weight of these devices. A technique is described where the device is implanted in the left perirenal space while an endovascular lead is used instead of an epicardial patch electrode. |
4,003 | [Heart rupture during pre-discharge stress test after myocardial infarction]. | A 65-year-old man with a postero-lateral myocardial infarction, complicated by rapid atrial fibrillation was admitted to the Intensive Coronary Care Unit. He received thrombolytic treatment. Electrocardiography and laboratory analysis were suggestive of reperfusion; the rapid atrial fibrillation was converted to sinus rhythm using i.v. amiodarone. Two echocardiograms performed on days 1 and 6 revealed hypokinesis of the postero-lateral wall and a mild reduction in the left ventricular ejection fraction. On day 7, after pharmacological wash-out, he was submitted to a bicycle exercise test: soon after the beginning of the 75 W step, the patient presented cardiac arrest due to electromechanical dissociation and hemopericardium. Despite prolonged cardiopulmonary resuscitation maneuvers and drainage of a few milliliters of pericardial blood, the patient did not survive. At autopsy, a huge clot filling the pericardial space was detected together with two linear 3 cm tears of the left ventricular lateral wall. The authors stress the possibility of unpredictable deaths during a pre-discharge exercise testing; good clinical judgment should therefore be used in deciding which patients should undergo this procedure and appropriate information about its potential risks should be given. |
4,004 | [Heart arrest]. | Cardiac arrest is one of the leading causes of mortality in industrialized countries and is mainly due to ischemic heart disease. According to ISTAT estimates, approximately 45,000 sudden deaths occur annually in Italy whereas according to the World Health Organization, its incidence is 1 per 1000 persons. The most common cause of cardiac arrest is ventricular fibrillation due to an acute ischemic episode. During acute ischemia the onset of a ventricular tachyarrhythmia is sudden, unpredictable and often irreversible and lethal. Each minute that passes, the probability that the patient survives decreases by 10%. For this reason, the first 10 min are considered to be priceless for an efficacious first aid. The possibility of survival depends on the presence of witnesses, on the heart rhythm and on the resolution of the arrhythmia. In the majority of cases, the latter is possible by means of electrical defibrillation followed by the reestablishment of systolic function. An increase in equipment alone does not suffice for efficacious handling of cardiac arrest occurring outside the hospital premises. Above all, an adequate intervention strategy is required. Ambulance personnel must be well trained and capable of intervening rapidly, possibly within the first 5 min. The key to success lies in the diffusion and proper use of defibrillators. The availability of new generation instruments, the external automatic defibrillators, encourages their widespread use. On the territory, these emergencies are the responsibility of the 118 organization based, according to the characteristics specific to each country, on the regulated coordination between the operative command, the crews and the first-aid means. Strategies for the handling of these emergencies within hospitals have been proposed by the Conference of Bethesda and tend to guarantee an efficacious resuscitation with a maximum latency of 2 min between cardiac arrest and the first electric shock. The diffusion of external automatic defibrillators is a preventive measure. Such equipment has permitted early defibrillation by non-medical first-aid personnel. These instruments contain software capable of recognizing an arrhythmia which may be defibrillated and of instructing the operator whether and when to press the defibrillation button. The latest instruments deliver the shock by means of a biphasic wave necessitating a lesser amount of energy which can be provided by lighter condensers. Thus such equipment weighs just a couple of kilograms. As suggested by ILCOR, for reasons of priority, such instruments should not only be available within hospitals and in ambulances but also on the territory, in particular in more crowded places. The availability of external automatic defibrillators in such places should reduce the time latency before intervention and thus increase survival. The ILCOR guidelines have suggested the constitution of an itinerary team well equipped for defibrillation and composed of trained personnel of State Institutions such as the Municipal Police, Traffic Police and the Fire Brigades. With regard to the majority of arrhythmias amenable to defibrillation which occur at home or in less crowded places, other strategies, such as primary prevention and training programs for categories at increased risk, must be employed. Antiarrhythmic drugs have long been considered the best solution for the prevention and treatment of ventricular tachyarrhythmias. However, the approach to these pathologies has drastically changed during the last few years owing to accumulating evidence in favor of defibrillators which may be implanted for the primary and secondary prevention of malignant ventricular arrhythmias. For patients with previous cardiac arrest, randomized studies have proven the advantages of such an approach compared to medical therapy. On the basis of the above, the guidelines for the use of antiarrhythmic implants have been modified. In most western countries, the laws regarding this aspect of medicine have recently been renewed. In the United States, where there is the "Law of the Good Samaritan", in order to protect and acquit persons who give first-aid, many states have adopted new laws which promote the use of external automatic defibrillators. Following recent dispositions by the President of the United States that defibrillators should be present in all Federal properties and on civil aircraft, a new Federal Law is about to pass. Italy lacks legislation regarding the use of defibrillators: in order to rectify this position, which is still anchored to existing dispositions of the civil and penal codes including those regarding the omission of first-aid, a bill entitled "The definition and modalities of the use of the external cardiac defibrillator" has recently been presented. |
4,005 | The efficacy of the Cox/maze procedure combined with mitral valve surgery: a matched control study. | To evaluate the results of the maze procedure combined with mitral valve (MV) surgery in patients with chronic atrial fibrillation (AF).</AbstractText>From 1994--1999, 47 patients with chronic AF underwent the maze procedure combined with MV surgery (maze group). They were compared to 47 patients matched for age, sex, left ventricular function and type of MV surgery (non-maze group). The maze group had less severe symptoms but larger left atrium, and AF of longer duration than the non-maze group. One surgeon performed all operations in both groups of patients.</AbstractText>There were two early deaths in the maze group (4.5%) and one (2.2%) in the non-maze group. The duration of cardiopulmonary bypass (P=0.0001) and aortic crossclamping (P=0.0001) were greater in the maze group. Mean follow-up was 26+/-3 months in the maze group and 32+/-4 months in the non-maze group, and was 100% complete. Three-year survival was 96+/-3% for the maze group compared to 85+/-7% for the non-maze group (P=0.16). At the latest follow-up, 75% of the maze patients were in sinus rhythm compared to 36% of the non-maze patients (P=0.0004); 38% of the maze group were on coumadin postoperatively, compared to 69% in the non-maze group (P=0.003); and patients in the maze group were on fewer antiarrhythmic medications (P=0.0002). Three-year freedom from thromboembolic complications was 100% for the maze group compared to 83+/-7% for the non-maze group (P=0.03).</AbstractText>In this retrospective study the maze procedure did not seem to increase operative mortality of MV surgery, was effective in eliminating atrial fibrillation, and reduced the risk of thromboembolic complications and the need for long-term anticoagulation after mitral valve repair or replacement with a bioprosthesis.</AbstractText> |
4,006 | Psychosocial nursing therapy following sudden cardiac arrest: impact on two-year survival. | Although psychosocial therapy has been shown to reduce mortality after myocardial infarction, it is unknown whether the benefits of psychosocial therapy on mortality reduction extend to out-of-hospital sudden cardiac arrest, a main cause of cardiovascular mortality.</AbstractText>Describe efficacy of psychosocial therapy on two-year cardiovascular mortality in sudden cardiac arrest survivors.</AbstractText>Survivors of out-of-hospital ventricular fibrillation or asystole (N = 129), documented by electrocardiograms from registries of a citywide Medic One unit and two countywide emergency units, were randomized into a two group, experimental, longitudinal design. The intervention consisted of 11 individual sessions, implementing three components: physiologic relaxation with biofeedback training focused on altering autonomic tone; cognitive behavioral therapy aimed at self-management and coping strategies for depression, anxiety, and anger; and cardiovascular health education. The primary outcome measure was cardiovascular mortality.</AbstractText>Risk of cardiovascular death was significantly reduced 86% by psychosocial therapy, p = .03. Six of the seven cardiovascular deaths in the control group were caused by ventricular arrhythmias. The cardiovascular death in the therapy group was due to stroke. Controlling for depression, previous myocardial infarction, low ejection fraction, decreased heart rate variability, and ventricular ectopic beats had little impact on estimated treatment effect. The risk of all-cause mortality was reduced by 62% in the therapy group, p = .13. There were a total of three deaths in the therapy group and eight deaths in the control group.</AbstractText>Psychosocial therapy significantly reduced the risk of cardiovascular death in sudden cardiac arrest survivors.</AbstractText> |
4,007 | Giant negative T waves during interferon therapy in a patient with chronic hepatitis C. | Interferon-alpha (IFN-alpha) has been widely used for treatment of chronic hepatitis C in Japan. In general, cardiovascular adverse reactions are rare in association with IFN-alpha therapy. Here, a 64-year-old man with chronic active hepatitis C complained of fatigue, palpitation and depression, and developed atrial fibrillation with prominent negative T waves during IFN-alpha therapy. Echocardiogram showed septal and apical hypertrophy. Three days after discontinuation of IFN-alpha, subjective symptoms and atrial fibrillation subsided. It is unclear whether or not IFN-alpha induced the giant negative T waves with apical hypertrophy. We might observe the developing course of hepatitis C virus (HCV)-related myocardial hypertrophy by chance. Cardiovascular toxicity should be carefully monitored during IFN-alpha therapy even in patients with minor cardiac disease, such as premature ventricular contracture (PVC) and mild hypertension. |
4,008 | Validation of a clinical decision aid to discontinue in-hospital cardiac arrest resuscitations. | Most patients undergoing in-hospital cardiac resuscitation do not survive to hospital discharge. In a previous study, we developed a clinical decision aid for identifying all patients undergoing resuscitation who survived to hospital discharge.</AbstractText>To validate our previously derived clinical decision aid.</AbstractText><AbstractText Label="DESIGN, SETTING, AND PARTICIPANTS" NlmCategory="METHODS">Data from a large registry of in-hospital resuscitations at a community teaching hospital in Georgia were analyzed to determine whether patients would be predicted to survive to hospital discharge (ie, whether their arrest was witnessed or their initial cardiac rhythm was either ventricular tachycardia or ventricular fibrillation or they regained a pulse during the first 10 minutes of chest compressions). Data from 2181 in-hospital cardiac resuscitation attempts in 1987-1996 involving 1884 pulseless patients were analyzed.</AbstractText>Comparison of predictions based on the decision aid with whether patients were actually discharged alive from the hospital.</AbstractText>For 327 resuscitations (15.0%), the patient survived to hospital discharge. For 324 of these resuscitations, the patients were predicted to survive to hospital discharge (sensitivity = 99.1%, 95% confidence interval, 97.1%-99.8%). In 269 resuscitations, patients did not satisfy the decision aid and were predicted to have no chance of being discharged from the hospital. Only 3 of these patients (1.1%) were discharged from the hospital (negative predictive value = 98.9%), none of whom were able to live independently following discharge from the hospital.</AbstractText>This decision aid can be used to help physicians identify patients who are extremely unlikely to benefit from continued resuscitative efforts.</AbstractText> |
4,009 | Variability of the QRS signal in high-resolution electrocardiograms and magnetocardiograms. | The variability of electric and magnetic signals from the heart during the depolarization phase is investigated. A signal processing method is developed, which provides estimates for the beat-to-beat variability of the QRS-complex. The method is based on the decomposition of the depolarization signal into bandpass signals by means of the Morlet wavelet transform. The beat variability of the depolarization signal is estimated by normalized variances of the envelope and instantaneous frequency of bandpass signals. Time intervals of the bandpass filtered depolarization signals having a high signal-to-noise ratio are selected applying an analysis based on phase statistics. The method was tested by computer simulation and experimental data taken from electrocardiographic and magnetocardiographic measurements of healthy persons and patients prone to malignant ventricular tachycardia (VT) or ventricular fibrillation (VF). Results suggest that the calculated variance parameters permit the characterization of beat variable depolarization signals and distinguish VT/VF patients from healthy persons. |
4,010 | Beneficial effects of astringinin, a resveratrol analogue, on the ischemia and reperfusion damage in rat heart. | Oxidative stress plays an important role in the pathogenesis of myocardial ischemia and infarction. Antioxidants might then be beneficial in the prevention of these diseases. Astringinin (3,3',4',5-tetrahydroxystilbene), a resveratrol (3,4',5-trihydroxystilbene) analogue with considerably higher antioxidative activity and free radical scavenging capacity, was introduced to examine its cardioprotective effects in ischemia or ischemia-reperfusion (I/R) rats. In the present study, the left main coronary artery was occluded by the following procedures: (i) 30 min occlusion, (ii) 5 min occlusion followed by 30 min reperfusion, and (iii) 4 h occlusion. Animals were infused with and without astringinin before coronary artery occlusion. Mortality, and the severity of ischemia- and I/R-induced arrhythmias were compared. Pretreatment of astringinin dramatically reduced the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) during either ischemia or I/R period. Astringinin at 2.5 x 10(-5) and 2.5 x 10(-4) g/kg completely prevented the mortality of animals during ischemia or I/R. During the same period, astringinin pretreatment also increased nitric oxide (NO) and decreased lactate dehydrogenase (LDH) levels in the carotid blood. In animals subjected to 4 h coronary occlusion, the cardiac infarct size (expressed as a percentage of occluded zone) was reduced from 44.4 + or - 4.1% to 19.1 + or - 2.4% by astringinin (2.5 x 10(-4) g/kg). We conclude that, astringinin is a potent antiarrhythmic agent with cardioprotective activity in ischemic and ischemic-reperfused rat heart. The beneficial effects of astringinin in the ischemic and ischemic-reperfused hearts may be correlated with its antioxidant activity and upregulation of NO production. |
4,011 | Comparison of the effects on drug concentrations, electrophysiologic parameters, and termination of atrial fibrillation in dogs when procainamide and ibutilide are delivered into the right atrium versus intravenously. | We tested the hypothesis that right intra-atrial (i.a.) administration of antiarrhythmic drugs resulted in higher peak serum drug concentrations, greater electrophysiologic effects, and greater efficacy for termination of atrial fibrillation (AF) than intravenous (i.v.) drug delivery.</AbstractText>Eight dogs were treated with 9.7 mg/kg procainamide infusion and eight dogs with 0.02 mg/kg ibutilide infusion, injected over 5 minutes. Each dog had both an electrophysiologic (EP) and an AF termination study during i.a. and i.v. drug administration at > or = 2-day intervals (total four studies each). Right atrial pacing capture threshold, right atrial effective refractory period (ERP), right atrial and right ventricular monophasic action potential (MAP) durations at 70% and 90% of repolarization (MAPD70, MAPD90), AH, HV, and QT intervals, QRS width, intra-arterial systolic and diastolic blood pressures, and cardiac output were measured at different time-points. Blood samples were drawn from the coronary sinus and femoral vein for drug level determination. The right atrium was paced at 400-msec cycle length throughout the study. AF was induced by rapid right atrial pacing and maintained by methacholine infusion at 1.5 to 3 microg/kg/min. The sustained AF was allowed to persist for 10 minutes before starting the antiarrhythmic drug infusion. We found no significant difference between the procainamide concentrations in the coronary sinus and femoral vein during i.a. and i.v. drug delivery. The time course and extent of increase in right atrial ERP, MAPD70, MAPD90, and all the other measured EP parameters did not differ between the two routes of drug administration. No significant difference was found in termination of AF between i.v. (5/7 procainamide; 4/8 ibutilide) or i.a. (3/8 procainamide; 3/8 ibutilide) drug delivery or between drugs (8/15 procainamide; 7/16 ibutilide).</AbstractText>Our data do not support any beneficial effect of i.a. versus i.v. procainamide or ibutilide delivery.</AbstractText> |
4,012 | Breakthrough waves during ventricular fibrillation depend on the degree of rotational anisotropy and the boundary conditions: a simulation study. | The left ventricle (LV) and right ventricle (RV) are characterized by specific fiber orientation known as "rotational anisotropy." However, it remains unclear whether the LV and RV are different with regard to the effect of rotational anisotropy on the dynamics of scroll waves during ventricular fibrillation (VF). To resolve this issue, we used a computation-based model to study scroll wave behavior.</AbstractText>We composed an environment of simulated three-dimensional ventricular wall slabs, with optional ratios of fiber rotation to wall thickness (0 degrees, 6 degrees, and 12 degrees/mm thickness; LV 10 mm, RV 5 mm), using Luo-Rudy phase I equations. When rotational anisotropy was not incorporated into the LV wall slab (theta endo to approximately theta epi = 0 degrees), most scroll waves rotated around the filaments perpendicular to the tissue surface, with only a few accompanying breakthrough waves. In a twisted LV model (theta endo to approximately theta epi = 60 degrees and 120 degrees), the scroll waves were demonstrated as multiple wavelets scattered spatiotemporally, frequently accompanied by breakthrough waves that were promoted by rotational anisotropy. In a twisted RV model (theta endo to approximately theta epi = 30 degrees and 60 degrees), single scroll waves and/or figure-of-eight reentrant waves appeared, with comparatively few breakthrough waves, regardless of the degree of fiber twist.</AbstractText>The proportion of electrical effects of rotational anisotropy and tissue boundaries plays an important role in the genesis of breakthrough waves during VF, and the difference in wave propagating patterns and frequency spectrum of the ventricles may arise, in part, from the number of breakthrough waves promoted by rotational anisotropy.</AbstractText> |
4,013 | Acute and long-term effects of atrioventricular junction ablation and VVIR pacemaker in symptomatic patients with chronic lone atrial fibrillation and normal ventricular response. | The precise role of irregular ventricular response in atrial fibrillation (AF) has not been fully elucidated. This study examined the independent effects of rhythm regularity in patients with chronic AF.</AbstractText>This study included 50 patients who had chronic lone AF and a normal ventricular rate. Among these patients, 21 who underwent AV junction ablation and implantation of a VVIR pacemaker constituted the ablation group; the other 29 patients were the medical group. Acute hemodynamic findings were measured in 21 ablation patients before ablation (during AF, baseline) and 15 minutes after ablation (during right ventricular pacing). Compared with baseline data, ablation and pacing therapy increased cardiac output (4.7 +/- 0.8 vs 5.2 +/- 0.9 L/min; P = 0.05), decreased pulmonary capillary wedge pressure (16 +/- 5 vs 13 +/- 4 mmHg; P = 0.001), and decreased left ventricular end-diastolic pressure (14 +/- 4 vs 11 +/- 3 mmHg; P < 0.05). After 12 months, the ablation group patients showed lower scores in general quality of life (-20%; P < 0.001), overall symptoms (-24%; P < 0.001), overall activity scale (-23%; P = 0.004), and significant increase of left ventricular ejection fraction (44% +/- 6% vs 49% +/- 5%; P = 0.02) by echocardiographic examination.</AbstractText>AV junction ablation and pacing in patients with chronic AF and normal ventricular response may confer acute and long-term benefits beyond rate control by eliminating rhythm irregularity.</AbstractText> |
4,014 | Regulation of ventricular fibrillation by heme oxygenase in ischemic/reperfused hearts. | We have assessed the relationship between reperfusion-induced ventricular fibrillation (VF) and heme oxygenase (HO) mRNA expression using northern blotting, reverse transcription-polymerase chain reaction (RT-PCR), and enzyme activity in isolated working ischemic/reperfused rat hearts. Isolated hearts were subjected to 30 min of global ischemia followed by 120 min of reperfusion. Upon reperfusion with VF, cardiac function was registered (n = 6 in each group), and HO mRNAs and enzyme activities were measured at the end of reperfusion in hearts that showed VF or did not develop VF. The expression of HO-1 mRNA (about fourfold) was observed in ischemic/reperfused nonfibrillated myocardium in comparison with the nonischemic control hearts. In those hearts when VF was developed, the expression of HO-1 mRNA was not observed in comparison with the nonischemic control myocardium. The results measured by RT-PCR and enzyme analysis support the data obtained by northern blotting. In additional studies, we decided to approach the question from a different angle. Thus, the purpose of our work was also to study the role of HO expression and enzyme activity in electrically fibrillated hearts without the ischemic/reperfused protocol. To simulate the period of 10 min of reperfusion-induced VF, hearts were electrically fibrillated, then defibrillated, and perfused for an additional 110 min, and HO-1 mRNA expression and enzyme activities were determined. Thus, electrically induced VF resulted in about 60%, 60%, and 70% reduction in HO-1 mRNA expression, RT-PCR signal intensity, and enzyme activity, respectively, compared with the nonfibrillated ischemic/reperfused group. In conclusion, our data provide evidence that the development of reperfusion-induced VF inhibits HO-1 mRNA expression and enzyme activity in both electrically fibrillated myocardium and ischemic/reperfused fibrillated hearts. The results clearly show that HO-1 mRNA expression and enzyme activity were increased in ischemic/reperfused nonfibrillated myocardium, suggesting that interventions that are able to increase HO-1 mRNA expression and enzyme activity may prevent the development of VF. |
4,015 | Long-term survival after ablation of the atrioventricular node and implantation of a permanent pacemaker in patients with atrial fibrillation. | In patients with atrial fibrillation that is refractory to drug therapy, radio-frequency ablation of the atrioventricular node and implantation of a permanent pacemaker are an alternative therapeutic approach. The effect of this procedure on long-term survival is unknown.</AbstractText>We studied all patients who underwent ablation of the atrioventricular node and implantation of a permanent pacemaker at the Mayo Clinic between 1990 and 1998. Observed survival was compared with the survival rates in two control populations: age- and sex-matched members of the Minnesota population between 1970 and 1990 and consecutive patients with atrial fibrillation who received drug therapy in 1993.</AbstractText>A total of 350 patients (mean [+/-SD] age, 68+/-11 years) were studied. During a mean of 36+/-26 months of follow-up, 78 patients died. The observed survival rate was significantly lower than the expected survival rate based on the general Minnesota population (P<0.001). Previous myocardial infarction (P<0.001), a history of congestive heart failure (P=0.02), and treatment with cardiac drugs after ablation (P=0.03) were independent predictors of death. Observed survival among patients without these three risk factors was similar to expected survival (P=0.43). None of the 26 patients with lone atrial fibrillation died during follow-up (37+/-27 months). The observed survival rate among patients who underwent ablation was similar to that among 229 controls with atrial fibrillation (mean age, 67+/-12 years) who received drug therapy (P=0.44).</AbstractText>In the absence of underlying heart disease, survival among patients with atrial fibrillation after ablation of the atrioventricular node is similar to expected survival in the general population. Long-term survival is similar for patients with atrial fibrillation, whether they receive ablation or drug therapy. Control of the ventricular rate by ablation of the atrioventricular node and permanent pacing does not adversely affect long-term survival.</AbstractText> |
4,016 | Assessment of left ventricular function by real-time 3-dimensional echocardiography compared with conventional noninvasive methods. | Quantitative assessment of left ventricular ejection fraction is an essential component of cardiac evaluation. We performed real-time 3-dimensional echocardiography in 56 consecutive patients who underwent multigated radionuclide angiography. Thirteen patients were excluded for the following reasons: 5 for large size of left ventricle required for image acquisition, 5 for suboptimal image quality in real-time 3-dimensional echocardiography, and 3 for atrial fibrillation. Finally, we compared left ventricular ejection fraction assessed by real-time 3-dimensional echocardiography and conventional 2-dimensional echocardiography with that obtained by multigated radionuclide angiography in 43 patients. Left ventricular ejection fraction was determined by real-time 3-dimensional echocardiography with the use of parallel plane-disks and sector plane-disks summation methods. A good correlation was obtained between both real-time 3-dimensional echocardiography methods and multigated radionuclide angiography (r = 0.87 and 0.90, standard error of estimate = 3.7% and 4.2%), whereas the relation between the 2-dimensional echocardiography method and radionuclide angiography demonstrated a significant departure from the line of identity (P <.001). In addition, interobserver variability was significantly lower (P <.05) for the real-time 3-dimensional echocardiography methods than that by the 2-dimensional echocardiography method. Real-time 3-dimensional echocardiography may be used for quantification of left ventricular function as an alternative to conventional methods in patients with adequate image quality. |
4,017 | Can seizures be the only manifestation of transient ischemic attacks? A report of four cases. | Several studies have investigated the frequency of epileptic seizures following ischemic strokes and transient ischemic attacks (TIAs). Little attention has been paid to the possibility that seizures may be precipitated by TIAs. We examined if seizures can be the only symptom of a TIA and how often this might occur. We performed a retrospective analysis of clinical charts and electroencephalograms of 160 consecutive patients evaluated for a first-ever seizure from January 1997 to December 1999 at Belluno General Hospital. From January to May 2000, 19 more first-ever seizure patients were evaluated directly. Four patients (2%) had seizures in the presence of important risk factors for ischemic stroke (atrial fibrillation in two patients, atrial fibrillation and ventricular mural thrombus in one patient, hemodynamically significant left carotid stenosis in one patient). Seizures were not accompanied by other neurological deficits or brain lesions on CT or MRI. As risk factors for brain ischemia are frequent in the general population not developing seizures, our results do not prove that the occurrence of seizures was more than casual in these patients. Yet they indicate that in a small percentage of patients, seizures can occur in a context highly suggestive of TIA, with no other focal deficits. |
4,018 | Should patients with hypertension receive antithrombotic therapy? | The main complications of hypertension, i.e. coronary heart disease, ischaemic strokes and peripheral vascular disease (PVD), are usually related to thrombosis. Increasing evidence also suggests that hypertension fulfils the components of Virchow's triad, thus conferring a prothrombotic or hypercoagulable state, as evident by abnormalities of haemostasis, platelets and endothelial function. It therefore seems plausible that use of antithrombotic therapy may help prevent these thrombosis-related complications of hypertension. Indeed, hypertensive patients with an estimated 10-year CHD risk > or = 15% will have their cardiovascular risk reduced by 25% using antihypertensive treatment, but the addition of aspirin further reduces major cardiovascular events by 15%. Recent guidelines recommend the use of aspirin 75 mg daily for hypertensive patients who have no contraindication to aspirin, in one of the following categories: (i) secondary prevention - cardiovascular complications (myocardial infarction, angina, non-haemorrhagic stroke, peripheral vascular disease or atherosclerotic renovascular disease); and (ii) primary prevention - those with blood pressure controlled to < 150/90 mmHg and one of: (a) age > or = 50 years and target organ damage (e.g. LVH, renal impairment, or proteinuria); (b) a 10-year CHD risk > or = 15%; or (c) type II diabetes mellitus. However, some of the risks of aspirin administration, namely increased incidence of major bleeding events, may possibly outweigh the benefits, especially in low-risk individuals. |
4,019 | Limited response to cardiac arrest by police equipped with automated external defibrillators: lack of survival benefit in suburban and rural Indiana--the police as responder automated defibrillation evaluation (PARADE). | To assess the out-of-hospital cardiac arrest (OHCA) survival advantage after providing police with automated external defibrillators (AEDs) in rural and suburban Indiana.</AbstractText>An observational evaluation was conducted in six Indiana counties (population: 464,741) before (retrospective) and after (prospective) training and equipping police with AEDs. The primary outcome evaluated was survival to hospital discharge for all cases of ventricular tachycardia/ventricular fibrillation (VT/VF) OHCA. Other factors evaluated include age, gender, race, arrest location, witnessed arrest, bystander cardiopulmonary resuscitation, response intervals, and survival to discharge for all OHCAs. Results are reported using chi-square, Student's t-test, and logistic regression.</AbstractText>Police were equipped with 112 AEDs, increasing total defibrillator capability by 43.2%. During the study period, AED-equipped police responded prior to emergency medical services (EMS) in 26 of 388 cases (6.7%). The time intervals from 911 call-to-scene and 911 call-to-shock were shortened by 1.6 minutes (95% confidence interval [95% CI] = 0.0 to 3.1, p = 0.05) and 4.8 minutes (95% CI = 1.3 to 8.3, p = 0.008), respectively, with police response as compared with EMS response. Survival to hospital discharge for VT/VF OHCA was 15.0% (3/20) in cases in which police responded first and 10.0% (16/160) in cases in which EMS responded first (relative risk [RR] 0.63, 95% CI = 0.17 to 2.39, p = 0.45). Survival to hospital discharge for VT/VF OHCA did not improve from the prestudy period (16/204, 7.8%) to after police AED availability (19/180, 10.6%) (RR 0.72, 95% CI = 0.36 to 1.45, p = 0.38).</AbstractText>Out-of-hospital cardiac arrest survival in suburban and rural Indiana did not improve after police were equipped with AEDs, likely related to poor police response.</AbstractText> |
4,020 | [Ventricular fibrillation secondary to radiofrequency application in ventricular tachycardia ablation]. | Radiofrequency catheter ablation has become a first line therapy for several types of tachycardias because of its high efficacy and low complication rate. The development of proarrhythmic complications due to a direct effect of radiofrequency is very unusual. We describe a patient with previous myocardial infarction and well tolerated sustained monomorphic ventricular tachycardia who underwent catheter ablation of the tachycardia substrate. During two of the radiofrequency applications, ventricular fibrillation developed and external defibrillation was required. |
4,021 | The protective effects of high dose ascorbic acid and diltiazem on myocardial ischaemia-reperfusion injury. | In this study, we aimed to compare the myocardial protective effects of high dose ascorbic acid with the effects obtained by adding diltiazem to high dose ascorbic acid. We studied 30 elective cardiac surgery patients prospectively. In ascorbic acid group (group AA), ascorbic acid was given after induction and just before aortic declamping, 50 mg.kg-1 each time. In ascorbic acid + diltiazem group (group AA + D), diltiazem was added to ascorbic acid (0.3 mg.kg-1, i.v. after induction and then 2 micrograms.kg-1 min-1 i.v. infusion until declamping). Group C was the control group. There was no significant difference between groups in terms of cardiac enzyme levels. After declamping, the arterial and coronary sinus malondialdehyde levels, measured as a marker of lipid peroxidation, were increased significantly in the group C while remained stable in the other two groups. Ventricular fibrillation (VF) after declamping was positive in 3, 1 and 6 patients in the groups AA, AA + D and C respectively. In this study, we observed the prevention of lipid peroxidation in the group AA and group AA + D. The only positive result obtained by addition of diltiazem to high dose ascorbic acid was the decrease in the frequency of VF after declamping. We concluded that the prevention of lipid peroxidation in the groups AA and AA + D provided no measurable protection over myocardial ischaemia-reperfusion injury. |
4,022 | Non-valvular atrial fibrillation and stroke prevention. National Blood Pressure Advisory Committee of the National Heart Foundation. | Atrial fibrillation (AF) affects 5% of people older than 65 years. Among patients with AF, the risk of stroke averages about 5% per year. The risk of stroke increases cumulatively with increasing age, previous transient ischaemic attack or stroke, hypertension, diabetes, impaired left ventricular function and a large left atrium. Management aims to identify and treat the underlying cause, control the ventricular rate, restore and maintain sinus rhythm, and minimise the risk of stroke. Warfarin reduces the risk of stroke by about two-thirds, and aspirin by about one-fifth. The risk of anticoagulant-associated haemorrhage increases with serious concomitant disease, and with poorly controlled hypertension and poorly controlled anticoagulation. All patients with chronic AF should be considered for oral anticoagulant therapy, and the decision based on the balance between the risks of thromboembolism and bleeding. The recommended INR (international normalised ratio) is 2.0-3.0. Treating 1,000 "average" AF patients (ie, those with a 5% per year risk of stroke) with warfarin prevents about 30 strokes and causes at least two episodes of major haemorrhage each year. Treating 1,000 |
4,023 | Clinical features of dilated cardiomyopathy in Great Danes and results of a pedigree analysis: 17 cases (1990-2000). | To determine clinical features of dilated cardiomyopathy (DCM) in Great Danes and to determine whether DCM is familial in this breed.</AbstractText>Retrospective study.</AbstractText>17 Great Danes with DCM.</AbstractText>Medical records of Great Danes in which DCM was diagnosed on the basis of results of echocardiography (fractional shortening < 25%, end-systolic volume index > 30 ml/m2 of body surface area) were reviewed. Pedigrees were obtained for affected animals, as well as for other Great Danes in which DCM had been diagnosed.</AbstractText>Dilated cardiomyopathy appeared to be familial and was characterized by ventricular dilatation, congestive heart failure (left-sided or biventricular), and atrial fibrillation. Pedigree analysis suggested that DCM was inherited as an X-linked recessive trait, but the mode of inheritance could not be definitively identified.</AbstractText>Results suggest that DCM may be an X-linked recessive trait in Great Danes. Thus, dogs with DCM probably should not be used for breeding, and female offspring of affected dogs should be used cautiously. Male offspring of affected females are at an increased risk of developing DCM and should be evaluated periodically for early signs of disease. Results of pedigree analysis were preliminary and should be used only as a guide for counseling breeders, rather than as a basis for making breeding decisions.</AbstractText> |
4,024 | The newer unconventional indications of permanent pacemakers. | In recent years, the indications for permanent pacemakers have expanded. The interest has focussed on hypertrophic cardiomyopathy, dilated cardiomyopathy and a new entity called hypertensive hypertrophy with cavity obliteration (HHCO). Pacemaker therapy is establishing itself for the prevention of atrial fibrillation. Pacing for neurocardiogenic syncope with newer pacing mode has encouraging datas. Pacemaker for long QT syndrome, after cardiac transplant and for haemodynamic improvement in occasional cases of first degree atrio-ventricular block is getting attention. The AHA and ACC guidelines updated in 1998 for implantation of cardiac pacemakers, now include several of these newer indications. |
4,025 | [Ventricular pre-excitation: electrophysiopathology, criteria for interpretation and clinical diagnosis. References for geriatrics]. | The authors review the state-of-the-art on ventricular pre-excitation in medical and arrhythmological literature in order to facilitate the recognition of the various clinical forms, like classic and occult Wolff Parkinson withe syndrome and Lown Ganong Levine syndrome. A historical introduction reviews our electrophysiopathological knowledge of the electrical activation and conduction of ventricular pre-excitation compared to normal, starting from the anatomic discovery of conduction pathways to the possible use of transesophageal electrostimulation and endocavity mapping to study electric potentials. Avantgarde technologies have also been developed to eliminate anomalous pathways firstly by using a direct current dirscharge and secondly radiofrequency. Atrioventricular electric activation has been widely illustrated in normal subjects in order to create a model for comparison with pathological ventricular pre-excitation: the upper left portion of the septum is no longer the first zone to trigger the kinetic mechanism compared to the early fascicular fraying of the homonymous branch. Instead the upper right part of the septum is activated earlier owing to the anomalous fascia connected on this side to the right branch through their septal arborisations. As a result, this new conduction pathway activates the ventricular masses earlier through an anomalous route, given that there is no further contact with the atrioventricular nodes which act as a control. A similar situation is found in the left branch block where the ventriculogram is late with a normal PR, unlike pre-excitation when an early delta wave is present with a short PR. Electric conduction is also illustrated based on new knowledge of the circuit structures and the rings theory. Orthodromic tachycardia is distinguished from the antidromic form, double accessory pathway tachycardia, ectopic reciprocant atrial fibrillation tachycardia and occult bundle tachycardia which is studied using transesophageal stimulation with a time threshold of 70 ms for ventricular-atrial retrograde activation. The stimulation techniques using single or repeated extrastimulus are explained for this purpose, as well as those with serial extrastimulation and the physical characteristics of the circuit based on the ratio between voltage and resistance. The authors also report the practical aims of electrostimulation for determining the electric threshold of the anomalous circuit in terms of refractoriness, electric atrial stability, reciprocity and the occurrence of the macro re-entry. Lastly, the authors describe electric conduction by anomalous pathways based on the criterion of conduction and activation, both of which are analysed and compared on the basis of the intrinsicoid deflection morphology on the surface ECG: the aberrant qRs usually suggests an antidromic ventricular activation and retrograde conduction between atrium and ventricle, while normal intrinsicoid deflection demonstrates that the activation is orthodromic and the conduction anterograde, namely ventricle-atrial. Having been reproduced in a synoptic synthesis, these manifestations show a regular electrophysiological pattern because they are dissimilar from the behaviour of the monophasic bioelectric potential of the cardiac cells specialised in the conduction of the stimulus, whether they represent a normal or pathological electric pathway. The study is rounded off by the analysis of the reciprocant tachycardias and their re-entry varieties related to the type of the anomalous bundles. A number of types of re-entry can be identified: sinusal re-entry (micro re-entry), atrial re-entry, re-entry in the atrio-ventricular node, re-entry tachycardia and the so-called triggered type. The discussion of the electrophysiopathological aspects of pre-excitation is followed by the clinical forms of ventricular pre-excitation that can be divided into 3 main types. The different ECG clinical pictures are set out in the summary table, together with the type of shunt and activation and possible variants, following Rosenbaum s classic paint: the common type B, the rare type A and a last variant, the C type. This section also describes the positional peculiarities of the Kent-Paladino bundle, the left ventricular, septal (anterior and posterior) and the multiple-bundle ones. The authors also illustrate the criterion and meaning of endocavity mapping in the search for anomalous bioelectric potentials that identify the pathway or the location of the endocardiac bundle and/or foci to be eliminated. A new echocardiographic technique is described with a conventional M mode, digitalised 2D and tissular Doppler which has a comparable ability to identify the anomalous pathways of electric conduction using a non-invasive method. (ABSTRACT TRUNCATED) |
4,026 | [Atrial fibrillation and thromboembolic events prevention. State of the art]. | Atrial Fibrillation (AF) is a common cardiac arrhythmia and stroke is its most devasting complication. The rate of ischemic stroke among people with AF is approximately six times that of people without AF and varies importantely with coexistent cardiovascular diseases; therefore stratification of AF patients into those at high and low risk of thromboembolism has become a crucial determinant of optimal antithrombotic prophylaxis. Multivaria-te analyses of prospective studies consistently show prior TIA/stroke, diabetes, age, heart failure to be independently predictive of stroke; left ventricular dysfunction is also strongly associated with stroke risk. Several randomized clinical trials demonstrated that treatment with adjusted-dose warfarin reduces the risk of stroke in AF patients by about two thirds. The efficacy of aspirin for prevention of stroke is controversial, but supported by pooled results of 3 placebo-controlled trials yelding a 21% reduction in stroke. The inherent risk of stroke should be considered in selection of AF patients for lifelong anticoagulation. Patients with AF and a recent stroke or TIA or multiple risk factors for stroke are likely to benefit from anticoagulation therapy; at present a target INR 2,5 appears optimal for most patients, although INR closer to 2.0 may be safer for patients at increased risk for bleeding events. The addition of aspirin to low- dose warfarin regimen does not provide any significant benefits and should be avoided. Therapy with aspirin is appropriate for patients who are at low risk of stroke or are unable to receive anticoagulants. AF patients treated with aspirin, should be periodically evaluated for development of high-risk features favoring anticoagulation. |
4,027 | Ventricular fibrillation refractory to automatic internal cardiac defibrillator in Fabry's disease. Review of cardiovascular manifestations. | Fabry's disease is a disorder of glycosphingolipid metabolism leading to alpha-galactosidase deficiency with systemic sequelae. Clinical cardiac manifestations include dysrhythmias, structural abnormalities apparent on echocardiography, and histologic changes secondary to glycosphingolipid deposition. The introduction of automated internal cardiac defibrillators (AICD) has been shown to decrease the incidence of circulatory collapse in individuals with known terminal arrhythmias. We present a patient with Fabry's disease, who underwent coronary angiography without finding of obstructive disease. He returned after aborted sudden cardiac death necessitating the placement of an AICD. He again presented after an episode of ventricular fibrillation refractory to internal defibrillation necessitating advanced life support, and subsequently expired. We review the electrocardiographic, cardiovascular structural, and histologic manifestations of Fabry's disease. |
4,028 | Simultaneous sternothoracic cardiopulmonary resuscitation: a new method of cardiopulmonary resuscitation. | No existing device for cardiopulmonary resuscitation (CPR) is designed to exploit both the "cardiac pump" and the "thoracic pump" effect simultaneously. The purpose of this study was to measure the haemodynamic effect of a new simultaneous sternothoracic cardiopulmonary resuscitation (SST-CPR) device that could compress the sternum and constrict the thoracic cavity simultaneously in a canine cardiac arrest model. After 4 min of ventricular fibrillation, 24 mongrel dogs were randomized to receive standard CPR (n=12) or SST-CPR (n=12). SST-CPR generated a new pattern of the aortic pressure curve presumed to be the result of both sternal compression and thoracic constriction. SST-CPR resulted in significantly higher mean arterial pressure than standard CPR (68.9+/-16.1 vs. 30.5+/-10.0 mmHg, P<0.01). SST-CPR generated higher coronary perfusion pressure than standard CPR (47.0+/-11.4 vs. 17.3+/-8.9 mmHg, P<0.01). End tidal CO(2) tension was also higher during SST-CPR than standard CPR (11.6+/-6.1 vs. 2.17+/-3.3 mmHg, P<0.01). In this preliminary animal model study, simultaneous sternothoracic cardiopulmonary resuscitation generated better haemodynamic effects than standard, closed chest cardiopulmonary resuscitation. |
4,029 | Reducing CPR artefacts in ventricular fibrillation in vitro. | CPR creates artefacts on the ECG, and a pause in CPR is therefore mandatory during rhythm analysis. This hands-off interval is harmful to the already marginally circulated tissues during CPR, and if the artefacts could be removed by filtering, the rhythm could be analyzed during ongoing CPR. Fixed coefficient filters used in animals cannot solve this problem in humans, due to overlapping frequency spectra for artefacts and VF signals. In the present study, we established a method for mixing CPR-artefacts (noise) from a pig with human VF (signal) at various signal-to-noise ratios (SNR) from -10 dB to +10 dB. We then developed a new methodology for removing CPR artefacts by applying a digital adaptive filter, and compared the results with this filter to that of a fixed coefficient filter. The results with the adaptive filter clearly outperformed the fixed coefficient filter for all SNR levels. At an original SNR of 0 dB, the restored SNRs were 9.0+/-0.7 dB versus 0.9+/-0.7 dB respectively (P<0.0001). |
4,030 | "Probability of successful defibrillation" as a monitor during CPR in out-of-hospital cardiac arrested patients. | The frequency spectrum of the ECG in ventricular fibrillation (VF) correlates with myocardial perfusion and might predict defibrillation success defined as return of spontaneous circulation (ROSC). The predictive power increases when more spectral variables are combined, but the complex information can be difficult to handle during the intensity of CPR. We therefore developed a method for expressing this multidimensional information in a single reproducible variable reflecting the probability of defibrillation success. This is based on the highest performing predictor for ROSC after 883 shocks given to 156 patients with VF. This was a combination of two decorrelated spectral features based on a principal component analysis of an original feature set with information on centroid frequency, peak power frequency, spectral flatness and energy. The function "Probability of defibrillation success" (P(ROSC)(v)) was developed by a 2-dimensional histogram technique. P(ROSC)(v) discriminated between shocks followed by ROSC and No-ROSC (P<0.0001). The present methodology indicates a possible way to develop a CPR monitor. |
4,031 | Contribution of peroxynitrite to the beneficial effects of preconditioning on ischaemia-induced arrhythmias in rat isolated hearts. | We studied the effects of urate, a peroxynitrite scavenger, on ischaemia- and peroxynitrite-induced preconditioning in rat isolated hearts. Isolated hearts perfused with Krebs-Henseleit solution were preconditioned either by 3 min of coronary artery occlusion or by peroxynitrite administration (1 microM) for 3 min, followed by 10 min of reperfusion and 30 min of coronary artery occlusion. Both ischaemia and peroxynitrite produced a marked reduction in arrhythmias. Urate (1 mM) added to the perfusate 10 min prior to ischaemic preconditioning or peroxynitrite infusion and maintained until coronary artery occlusion, markedly reversed the beneficial effects in the ischaemic and peroxynitrite-treated groups. Urate administration in the peroxynitrite-treated group increased the incidence of ventricular tachycardia from 57% (n = 11) to 100% (n = 6) and total ventricular fibrillation from 0% (n=0) to 44% (n=4). Similarly, urate augmented the incidence of ventricular tachycardia from 47% (n=8) to 85% (n = 6) in the ischaemic preconditioning group. On its own, urate did not affect the severity of cardiac arrhythmias. Peroxynitrite infusion caused a marked increase in the effluent nitrate levels, from 0.05 +/- 0.1 microM (n = 5) to 0.4 +/- 0.2 microM (n = 6), and urate significantly decreased these levels to 0.08 +/- 0.03 microM (n = 9). These results suggest that peroxynitrite at low concentrations contributes to the beneficial effects of preconditioning on ischaemia-induced arrhythmias in rat isolated hearts. |
4,032 | Scaling exponent predicts defibrillation success for out-of-hospital ventricular fibrillation cardiac arrest. | -Defibrillator shocks often fail to terminate ventricular fibrillation (VF) in out-of-hospital cardiac arrest (OOHCA), and repeated failed shocks can worsen the subsequent response to therapy. Because the VF waveform changes with increasing duration of VF, it is possible that ECG analyses could estimate the preshock likelihood of defibrillation success. This study examined whether an amplitude-independent measure of preshock VF waveform morphology predicts outcome after defibrillation. Methods and Results-Clinical data and ECG recordings from an automated external defibrillator were obtained for 75 subjects with OOHCA in a suburban community with police first responders and a paramedic-based emergency medical system. An estimate of the fractal self-similarity dimension, the scaling exponent, was calculated off-line for the VF waveform preceding shocks. Success of the first shock was determined from the recordings. Return of pulses and survival were determined by chart review. The first shock resulted in an organized rhythm in 43% of cases, and 17% of cases survived to hospital discharge. A lower mean value of the scaling exponent was observed for cases in which the first defibrillation resulted in an organized rhythm (P:=0.004), for cases with return of pulses (P:=0.049), and for cases surviving to hospital discharge (P:<0.001). Receiver operator curves revealed the utility of the scaling exponent for predicting the probability of restoring an organized rhythm (area under the curve=0.70) and of survival (area under the curve=0.84).</AbstractText>-The VF waveform in OOHCA can be quantified with the scaling exponent, which predicts the probability of first-shock defibrillation and survival to hospital discharge.</AbstractText> |
4,033 | The effects of positive end-expiratory pressure during active compression decompression cardiopulmonary resuscitation with the inspiratory threshold valve. | The use of an inspiratory impedance threshold valve (ITV) during active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) improves perfusion pressures, and vital organ blood flow. We evaluated the effects of positive end-expiratory pressure (PEEP) on gas exchange, and coronary perfusion pressure gradients during ACD + ITV CPR in a porcine cardiac arrest model. All animals received pure oxygen intermittent positive pressure ventilation (IPPV) at a 5:1 compression-ventilation ratio during ACD + ITV CPR. After 8 min, pigs were randomized to further IPPV alone (n = 8), or IPPV with increasing levels of PEEP (n = 8) of 2.5, 5.0, 7.5, and 10 cm H(2)O for 4 consecutive min each, respectively. Mean +/- SEM arterial oxygen partial pressure decreased in the IPPV group from 150 +/- 30 at baseline after 8 min of CPR to 110 +/- 25 torr at 24 min, but increased in the PEEP group from 115 +/- 15 to 170 +/- 25 torr with increasing levels of PEEP (P <0.02 for comparisons within groups). Mean +/- SEM diastolic aortic minus diastolic left ventricular pressure gradient was significantly (P < 0.001) higher after the administration of PEEP (24 +/- 0 vs 17 +/- 1 mm Hg with 5 cm H(2)O of PEEP, and 26 +/- 0 vs 17 +/- 1 mm Hg with 10 cm H(2)O of PEEP), whereas the diastolic aortic minus right atrial pressure gradient (coronary perfusion pressure) was comparable between groups. Furthermore, systolic aortic pressures were significantly (P < 0.05) higher with 10 cm H(2)O of PEEP when compared with IPPV alone (68 +/- 0 vs 59 +/- 2 mm Hg). In conclusion, when CPR was performed with devices designed to improve venous return to the chest, increasing PEEP levels improved oxygenation. Moreover, PEEP significantly increased the diastolic aortic minus left ventricular gradient and did not affect the decompression phase aortic minus right atrial pressure gradient. These data suggest that PEEP reduces alveolar collapse during ACD + ITV CPR, thus leading to an increase in indirect myocardial compression.</AbstractText>Inspiratory impedance during active compression-decompression cardiopulmonary resuscitation improves perfusion pressures, and vital organ blood flow during cardiac arrest. Increasing levels of positive end-expiratory pressure during performance of active compression-decompression cardiopulmonary resuscitation with an inspiratory impedance valve improves oxygenation, and increases the diastolic aortic-left ventricular pressure gradient and systolic arterial blood pressure.</AbstractText> |
4,034 | The effect of insulin cardioplegia on atrial fibrillation after high-risk coronary bypass surgery: a double-blinded, randomized, controlled trial. | Atrial fibrillation after coronary bypass (CABG) surgery is an important cause of morbidity and increased resource utilization. Insulin-enhanced cardioplegia may reduce postoperative arrhythmias by improving aerobic myocardial metabolism and mitigating the deleterious effects of ischemia. We performed a double-blinded, randomized, controlled clinical trial to determine if insulin-enhanced cardioplegia decreases the risk of post-CABG atrial fibrillation in a high-risk patient population. We randomized 501 patients undergoing urgent CABG to receive insulin-enhanced (Humulin R 10 IU/L, Insulin group, n = 243) or standard (Control group, n = 258) blood cardioplegia during cardiopulmonary bypass. Patients were monitored by using continuous electrocardiography for a minimum of 3 days postoperatively. All standard cardiac medications, including beta-adrenergic blockers, were continued postoperatively. Insulin-enhanced cardioplegia did not result in a significant reduction in postoperative atrial fibrillation. Furthermore, we failed to detect a difference in the incidence of conduction defects, ventricular tachycardia, or pacemaker requirements between insulin and placebo patients. Atrial fibrillation was the most common arrhythmia, occurring in 31% of all patients. Independent predictors of atrial fibrillation were elderly age, preoperative atrial fibrillation, and renal insufficiency. Right bundle branch block was the most common conduction abnormality. Predictors of right bundle branch block were elderly age, female sex, and circumflex coronary artery disease. The incidence of postoperative ventricular tachycardia, left bundle branch block, and permanent pacemaker requirement was small. We conclude that insulin-enhanced cardioplegia does not reduce the incidence of postoperative atrial fibrillation in high-risk CABG patients.</AbstractText>We conducted a double-blinded, randomized, placebo-controlled trial of insulin-enhanced cardioplegia in 501 patients undergoing urgent coronary bypass surgery. Insulin did not decrease the incidence of postoperative atrial fibrillation when compared with placebo. We also failed to demonstrate a difference in the incidence of other postoperative arrhythmias between the two groups of patients.</AbstractText> |
4,035 | Current approaches to evaluation and management of patients with ventricular arrhythmias. | The clinical manifestations of ventricular arrhythmias encompass a broad spectrum, from complete absence of symptoms to sudden death. Although our understanding of the pathophysiology and natural history of these arrhythmias has advanced significantly over the past decade, large gaps in our knowledge remain, especially in patients with heart failure not due to coronary artery disease. We have learned much about the appropriate roles of antiarrhythmic drugs and implantable defibrillators in the prevention of sudden death. Studies performed over the past decade have made clear that the primary treatment for patients at high risk for life-threatening ventricular arrhythmias should be the implantable defibrillator. However, specific syndromes causing ventricular tachyarrhythmias are being recognized, and care must be individualized. Although hospital mortality from acute myocardial infarction has decreased as a result of newer therapies, sudden death after hospital discharge remains an important problem, causing at least 30% of post-infarction deaths, even in patients who have received thrombolytic therapy. Two independent studies have confirmed that patients with asymptomatic non-sustained ventricular tachycardia in the presence of left ventricular ejection fraction < .40 after myocardial infarction who have sustained ventricular tachycardia inducible by electrophysiologic study are at significant risk for sudden death. This risk is significantly reduced by ICD, but not pharmacologic, antiarrhythmic therapy. Our major challenge at this time is not how best to treat high risk patients, but how best to identify them prior to events. Finally, physicians should be aware that many symptomatic ventricular tachycardias are now curable at low risk, using catheters to deliver radiofrequency energy. |
4,036 | Sotalol vs metoprolol for ventricular rate control in patients with chronic atrial fibrillation who have undergone digitalization: a single-blinded crossover study. | To compare the effects of sotalol and metoprolol on heart rate, during isotonic (ITE) and isometric (IME) exercise and daily activities, in digitalized patients with chronic atrial fibrillation.</AbstractText>The study had a randomized, single-blinded, crossover design. Twenty-three patients with chronic atrial fibrillation received placebo for 4 weeks, followed by a 4-week period of treatment with sotalol and metoprolol in random order. At the end of each period, the patients were assessed with 24-h ECG monitoring, a cardiopulmonary exercise test and a handgrip manoeuvre. Both agents produced a lower heart rate than placebo at rest and at all levels of isotonic exercise (P < 0.001) without affecting oxygen uptake. Sotalol produced a lower heart rate than metoprolol only at submaximal exercise (116 +/- 9 bpm for sotalol vs 125 +/- 11 bpm for metoprolol, P < 0.001). During isometric exercise, sotalol produced a lower maximum heart rate than did metoprolol (113 +/- 22 vs 129 +/- 18 bpm, respectively). Both agents produced a lower mean heart rate than placebo over 24 h (P < 0.001 for all), while sotalol produced a lower mean heart rate than metoprolol during the daytime (P < 0.01).</AbstractText>Sotalol is a safe and effective agent for control of heart rate in digitalized patients with atrial fibrillation. Sotalol is superior to metoprolol at submaximal exercise, resulting in better rate control during daily activities.</AbstractText> |
4,037 | Inactivation of a ventricular tachycardia preventive algorithm during automatic mode switching for atrial tachyarrhythmia. | A patient with a dual chamber implantable defibrillator and pause dependent VT in whom a rate smoothing algorithm failed to operate during automatic mode switching due to device idiosyncrasy is reported. Preventive measures are discussed. |
4,038 | Unipolar defibrillator? | An unusual case of "unipolar" pacing and myopotential over-sensing leading to an inappropriate ICD shock in a patient with an implanted defibrillator is reported. The reasons for unipolar behavior in a system using a committed bipolar device are discussed. |
4,039 | Inappropriate shock therapy in a heart failure defibrillator. | A 63-year-old male with dilated cardiomyopathy underwent implantation of a "heart failure" defibrillator capable of biventricular pacing. He received an inappropriate shock 5 hours after the procedure. Stored electrograms revealed that during each sinus beat the ventricular channel recorded up to three separate events. These resulted from far-field atrial sensing by the coronary venous lead, appropriate right ventricular sensing, then delayed left ventricular sensing (the result of left bundle branch block). As a consequence of far-field left atrial sensing the two subsequent ventricular electrograms fell within the VF zone. Following an atrial premature beat, VF detection criteria were satisfied and shock therapy delivered. Although coronary venous lead repositioning eliminated far-field atrial sensing, double counting of the widely split right and left ventricular electrograms still occurred during sinus rhythm. Shortening the programmed AV delay resulted in constant biventricular pacing with a single electrogram. |
4,040 | Discrimination between ventricular and supraventricular tachycardia by dual chamber cardioverter defibrillators: importance of the atrial sensing function. | Although the addition of atrial sensing in dual chamber ICDs may improve the ability of the device to discriminate between supraventricular (SVT) and ventricular tachycardia (VT), atrial sensing errors may also negatively affect tachycardia classification. This prospective study evaluated the incidence of atrial sensing errors in a dual chamber ICD and their impact on VT/SVT discrimination. In 145 patients, a dual chamber ICD (Defender) was implanted. Analysis of 1,241 tachycardia episodes stored during a mean follow-up of 14+/-8 months revealed atrial sensing errors in 817 (66%) episodes. Upon expert review, device-based classification was confirmed in 509 (98%) of 522 SVT episodes. No false device-based SVT classification was related to atrial sensing errors. Of 719 episodes classified as VT by the device, 645 (90%) were confirmed. There were 74 episodes of false-positive VT detection. Of these, 63 were related to atrial sensing errors: atrial undersensing in 58 (92%) and atrial oversensing in 5 (8%) episodes. Atrial sensing errors led to incorrect VT/SVT discrimination in 51 (4%) of 1,241 episodes. Only the occurrence of paroxysmal atrial fibrillation and abdominal site of device implantation showed a significant influence on false VT/SVT discrimination. Atrial sensing errors are frequently encountered in dual chamber ICDs. Due to the VT/SVT discrimination algorithm, atrial sensing errors only led to misclassification in 4 % of all episodes, mainly due to atrial undersensing. No VT underdetection due to atrial oversensing occurred. |
4,041 | Thrombolysis and antithrombotic therapy for coronary artery disease. | Aspirin in a dose of 160 to 325 mg should be administered on day 1 of an acute MI and continued indefinitely on a daily basis. Thrombolytic therapy should be administered within 6 to 12 hours after the onset of an acute MI with ST segment elevation or with left bundle branch block. Primary coronary angioplasty when available should be used rather than thrombolytic therapy in the treatment of older persons with acute MI who are poor candidates for thrombolytic therapy. Intravenous heparin should be given in persons with acute MI undergoing primary coronary angioplasty or surgical coronary revascularization and in persons with acute MI at high risk for systemic embolization. Long-term oral warfarin should be given after MI for the secondary prevention of MI in post-MI persons unable to tolerate daily aspirin, in post-MI persons with persistent atrial fibrillation, and in post-MI persons with left ventricular thrombus. Platelet GP IIb/IIIa inhibitors should be administered along with aspirin and enoxaparin in the acute phase of management of persons with unstable angina pectoris or non-Q wave MI. Aspirin should be administered daily indefinitely to persons after MI, to persons with unstable angina pectoris, to persons with stable angina pectoris, and to persons undergoing coronary revascularization. Aspirin plus ticlopidine or aspirin plus clopidogrel should be used in persons undergoing coronary artery stenting. Platelet GP IIb/IIIa inhibitors should be used at the time of coronary angioplasty, coronary atherectomy, or coronary stenting. Aspirin, 160 to 325 mg daily, is recommended in older men and postmenopausal women who are at high risk for developing coronary events in addition to treating their coronary risk factors. |
4,042 | Antithrombotic therapy in atrial fibrillation. | Atrial fibrillation is a common condition affecting elderly individuals; as many as 10% of people older than age 80 years have AF. AF is also a potent risk factor for ischemic stroke, raising the risk of stroke fivefold. A set of consistent randomized controlled trials has demonstrated that long-term anticoagulation can largely reverse the risk of stroke attributable to AF. In these trials, anticoagulation generally proved quite safe, raising the risk of intracranial hemorrhage by less than 0.5% per year. The anticoagulation target for AF is INR 2 to 3 with INR 2.5 as the specific goal. The trials were much less consistent about the efficacy of aspirin, although it seems that aspirin has a small stroke-preventive effect. The recommended dose of aspirin is 325 mg per day. Because it raises the risk of hemorrhage and adds the burden of frequent monitoring of INR values, anticoagulation is recommended for those patients with AF at higher risk of stroke. Such higher risk is conferred by the following risk factors: (1) a history of a prior stroke, TIA, or other systemic embolic event; (2) a history of hypertension; (3) diabetes mellitus; (4) left ventricular dysfunction; (5) mitral stenosis; and (6) older age. The exact age threshold conferring sufficiently increased risk is uncertain, with some research indicating the threshold should be age 65 years, and other research indicating the threshold should be age 75 years. For lower-risk patients, aspirin is recommended. Future research should focus on the oldest patients with AF. These individuals face the highest risk of ischemic stroke without anticoagulation and the highest risk of major hemorrhage with anticoagulation. Only small numbers of such elderly patients were included in the randomized trials. Future research should also focus on improved risk stratification, allowing better targeting of anticoagulation. Discoveries of new antithrombotic agents and new drugs and devices for preservation of sinus rhythm could radically improve stroke-preventive strategies for AF. |
4,043 | Initial experience with an autocapture pacemaker system. | Autocapture management aims to extend pacemaker longevity without compromising on patient safety by automatically monitoring the pacing threshold and adjusting the pacemaker output for consistent capture. This paper describes our initial experience with the Pacesetter Regency pacemaker with autocapture management.</AbstractText>Nineteen patients were implanted with single chamber pacemakers with autocapture management. Autocapture was programmed "ON" the day after implantation if Evoked Response (ER) amplitude was at least 2.8 mV. The patients were followed up at 2 weeks, 2 months and 6 months. At each visit, pacing threshold and lead impedance were measured. Autocapture was turned "ON" during follow-up if it had not been done previously.</AbstractText>In 16 out of 19 patients, autocapture could be turned "ON" the day after implantation. One patient had an ER signal that was less than 2.8 mV and 2 patients were in fast atrial fibrillation of more than 120 beats per minute which precluded ER signal testing. These patients could not have autocapture programmed "ON".</AbstractText>The benefits of autocapture management can only be realised if an ER signal of at least 2.8 mV is obtained. This requires intraoperative testing of the ER signal. Since there is no commercially available pacing system analyser presently that can measure this, modification of the standard implantation procedure with some prolongation of procedure time is needed.</AbstractText> |
4,044 | Oral amiodarone for prevention of atrial fibrillation after open heart surgery, the Atrial Fibrillation Suppression Trial (AFIST): a randomised placebo-controlled trial. | Beta-blockers and amiodarone reduce the frequency of atrial fibrillation after open-heart surgery but the effectiveness of oral amiodarone in older patients already receiving beta-blockers is unknown. We have assessed the efficacy of oral amiodarone in preventing atrial fibrillation in patients aged 60 years or older undergoing open-heart surgery.</AbstractText>We did a randomised, double-blind placebo-controlled trial in which patients undergoing open-heart surgery (n=220, average age 73 years) received amiodarone (n=120) or placebo (n=100). Patients enrolled less than 5 days before surgery received 6 g of amiodarone or placebo over 6 days beginning on preoperative day 1. Patients enrolled at least 5 days before surgery received 7 g over 10 days beginning on preoperative day 5.</AbstractText>Patients on amiodarone had a lower frequency of any atrial fibrillation (22.5% vs 38.0%; p=0.01; absolute difference 15.5% [95% CI 3.4-27.6%]), and there were significant differences in favour of the active drug for symptomatic atrial fibrillation (4.2% vs 18.0%, p=0.001), cerebrovascular accident (1.7% vs 7.0%, p=0.04), and postoperative ventricular tachycardia (1.7% vs 7.0%, p=0.04). Beta-blocker use (87.5% amiodarone vs 91.0% placebo), nausea (26.7% vs 16.0%), 30-day mortality (3.3% vs 4.0%), symptomatic bradycardia (7.5% vs 7.0%), and hypotension (14.2% vs 10.0%) were similar.</AbstractText>Oral amiodarone prophylaxis in combination with beta-blockers prevents atrial fibrillation and symptomatic fibrillation and reduces the risk of cerebrovascular accidents and ventricular tachycardia.</AbstractText> |
4,045 | Radiofrequency ablation: a cure for tachyarrhythmias. | Radiofrequency (RF) ablation is a new modality of pennanently curing patients with various tachycardias using radiofrequency energy, a technique evolved in the past decade. RF ablation was performed on 913 patients with different tachyarrhythmias from April, 1994 to July, 1999. There were 491 men and 422 females aged 42 +/- 34 years (range 1 to 76 years). Supraventricular tachycardia (SVT) was present in 462 patients, accessory pathway mediated atrioventricular re-entrant tachycardia (AVRT) in 355 patients (377 accessory pathways) and idiopathic ventricular tachycardia (VT) in 96 patients. Amongst the patients with SVT, 402 had atrioventricular nodal re-entrant tachycardia (AVNRT), 22 had atrial flutter, 20 had ectopic atrial tachycardia and 18 had atrial fibrillation. RF successfully abolished the tachycardia in 400/402 patients (99.5%) with AVNRT, 330/377 (87.5%) accessory pathways in patients with AVRT, 14/22 patients (63.6%) of atrial flutter, 18/20 patients (90%) of atrial tachycardia and 79/96 patients (82.3%) with idiopathicVT. Successful AV nodal ablation with pacemaker implantation was done in 10/18 patients with chronic atrial fibrillation with fast ventricular rate and tachycardia induced cardiomyopathy. AV nodal modulation for atrial fibrillation was tried in the remaining 8 patients and was successful in 4 (4/8). The overall success rate for all arrhythmias was 93.6%, and there was no mortality. At a follow-up of 6.8 +/- 5.4 months, there was a recurrence in 34/420 patients (8%), in whom successful re-ablation was performed. One patient with AVNRT and another with a parahisian pathway developed complete heart block and were given pacemakers. One patient developed inferior wall infarction on the next day post RF. There were 4 patients who had pericardial tamponade necessitating pericardiocentesis and 2 patients developed deep vein thrombosis, which was treated conservatively. Thus RF ablation is an effective, safe and curative therapy for various arrhythmias. |
4,046 | Cellular and ionic mechanisms responsible for the Brugada syndrome. | The Brugada syndrome is characterized by ST-segment elevation in the right precordial leads, V1-V3 (unrelated to ischemia or structural disease), normal QT intervals, RBBB pattern, and sudden cardiac death, particularly in men of Asian origin. An autosomal dominant mode of inheritance with variable penetrance is generally observed. The only gene mutations thus far linked to the Brugada Syndrome appear in the alpha subunit of the gene that encodes for the cardiac sodium channel, SCN5A. An outward shift in the balance of currents contributing to phase 1 of the right ventricular action potential is thought to underline to electrocardiographic manifestation of the syndrome. Strong sodium channel block, among other modalities, can accentuate the action potential notch in right ventricular epicardial cells, eventually leading to loss of the action potential dome. This results in the development of a large dispersion of repolarization within epicardium as well as between epicardium and endocardium, providing the substrate for the development of phase 2 and cirus movement reentry, which underline VT/VF. Therapy is directed at restoring the balance of current via inhibition of the transient outward current, Ito, and/or stimulation of inward calcium using beta adrenergic agonists, among several strategies. |
4,047 | Evidence of heterogeneous remodeling in canine atrial fibrillation. | Although electrophysiologic changes occur during atrial remodeling, little is known how remodeling affects atrial fibrillation (AF) organization. We hypothesized that, in animals with long-term rapid atrial rates and a rapid ventricular response, AF would be more disorganized than in animals with rapid atrial rates only. In 8 dogs, chronic AF was created by 6 weeks of continuous rapid atrial pacing. In this group, the ventricular response to AF was spontaneous and unaltered. Twenty-one epochs of AF were epicardially mapped from the right and left atria. In 6 dogs, chronic AF was also created with rapid atrial pacing, however, the AV node was ablated and the ventricles were VVI paced at 80 BPM. Only 1 epoch of AF per dog was mapped. Atrial cycle length (CL) and spatial organization were compared. In chronic AF with a spontaneous ventricular rate, left atrial CL (96+/-14 ms) averaged 24 ms shorter than right atrial CL (121+/-18 ms) (P < .0001). With VVI pacing, AF CL was longer than in the dogs with the spontaneous ventricular rate. However, the left atrial CL (109+/-30 ms) was still significantly shorter than the right atrial CL (145+/-43 ms) (P < .001). Spatial organization values showed that during chronic AF with a spontaneous ventricular rate, the left atrium is more disorganized (2593+/-497) than the right atrium (2052+/-732) (P < .0001). With VVI pacing, the left atrium (2202+/-597) is still more disorganized than the right (1620+/-936) (P < .05). However, with VVI pacing, both atria appear less disorganized than dogs with VVI pacing. Atrial remodeling caused by heart failure that is superimposed on the remodeling due to rapid atrial rates causes the atria to be more disorganized than remodeling due to rapid atrial rates alone. However, in either case the left atrium is faster and more disorganized than the right atrium. Atrial fibrosis caused by the heart failure may increase the disorganization of AF activation. |
4,048 | Genetics of brugada, long QT, and arrhythmogenic right ventricular dysplasia syndromes. | This article outlines the up-to-date understanding of the molecular basis of primary ventricular arrhythmias. Two disorders have recently been well described at the molecular level, the long QT syndromes and Brugada syndrome, and this article reviews the current scientific knowledge of each disease. A third disorder, arrhythmogenic right ventricular dysplasia, which is on the cusp of understanding, will also be described. |
4,049 | Electrocardiographic features of inherited diseases that predispose to the development of cardiac arrhythmias, long QT syndrome, arrhythmogenic right ventricular cardiomyopathy/dysplasia, and Brugada syndrome. | Analysis of the 12-lead electrocardiogram (ECG) provides important diagnostic and prognostic information in the long QT syndrome. The clinical diagnosis of long QT syndrome is determined by the presence of a QTc > or = 0.44 sec. A normal QTc does not exclude a family member from being a genetic carrier. The ECG patterns of depolarization, the ST segment and shape of the T-wave can provide important clues as to the affected gene, particularly in conjunction with clinical information as to the precipitating causes of syncope or cardiac events. In arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D), the typical ECG pattern consists of T-wave inversion beyond lead V1. Evidence of right ventricular parietal block is manifest by a QRS duration in V1 > or = 110 msec and a longer QRS duration in the right then left precordial leads. Evidence of slow fractionated conduction is present as epsilon waves. The signal averaged ECG may show exceedingly long and low late potentials. Information regarding the risk of sudden death may also be obtained from the ECG. The ECG changes alone or in combination can provide strong evidence for the diagnosis of ARVC/D and helps to differentiate ARVC/D from right ventricular outflow tract (RVOT) tachycardia. The typical pattern of the ECG in the Brugada syndrome is ST segment elevation in the right precordial leads. This abnormality can be dormant and elicited by administration of drugs that cause Na channel blockade, such as ajmaline or type 1a or 1C antiarrhythmic drugs. Individuals who do not have the Brugada ECG findings at baseline but have this pattern induced by antiarrhythmic drugs are also at risk for sudden death. Further risk stratification may be obtained in the asymptomatic patients if ventricular fibrillation is induced at electrophysiological study. |
4,050 | Predicting response to carvedilol for the treatment of heart failure: a multivariate retrospective analysis. | Carvedilol has been shown to decrease the progression of heart failure and improve left ventricular function and survival in patients with a left ventricular ejection fraction (LVEF) less than 35%. However, not all patients respond uniformly to this therapy. We proposed to identify variables that could, potentially, be used to predict response to carvedilol therapy as measured by the change in LVEF after treatment (Delta LVEF), and to identify pretreatment variables associated with hospitalization for heart failure after carvedilol therapy.</AbstractText>A retrospective analysis of 98 patients treated with open-label carvedilol for a mean period of 16 months was performed by using bivariate and step-wise multivariate analyses. Bivariate analysis showed a positive correlation of Delta LVEF with heart rate at baseline (P =.001). There was a negative correlation of Delta LVEF with baseline LVEF (P <.01), diabetes mellitus (P =.04), and ischemic cardiomyopathy (P =.0002). Multivariate analysis showed a positive correlation of Delta LVEF with heart rate at baseline (P =.01) and a negative correlation with initial LVEF (P =.02) and ischemic cardiomyopathy (P =.006). Variables associated with hospitalization after initiation of carvedilol therapy were New York Heart Association (NYHA) classification (P =.001), lower extremity edema (P =.001), presence of an S3 (P =.02), hyponatremia (P =.02), elevated blood urea nitrogen (BUN) (P =.002), atrial fibrillation (P =.001), diabetes mellitus (P =.02), and obstructive sleep apnea (P =.009).</AbstractText>Heart failure patients with the lowest LVEF or the highest heart rate at baseline had the greatest gain in LVEF after treatment with carvedilol. Patients with ischemic cardiomyopathy derived less benefit. Patients with clinical evidence of decompensated heart failure were at greater risk for hospitalization after initiation of carvedilol therapy.</AbstractText> |
4,051 | Pause-dependent polymorphic ventricular tachycardia during long-term treatment with dofetilide: a placebo-controlled, implantable cardioverter-defibrillator-based evaluation. | To compare the incidence of pause-dependent polymorphic ventricular tachycardia (PVT) in patients with implantable cardioverter-defibrillators (ICDs) randomly assigned to the QT-prolonging antiarrhythmic dofetilide or placebo.</AbstractText>Drug-related torsade de pointes (TdP) is usually recognized within days of initiating therapy, but its incidence during long-term therapy is unknown.</AbstractText>We assessed the frequency of TdP and ICD electrograms compatible with TdP in a multicenter study that randomized ICD patients to placebo (n = 87) or dofetilide (n = 87). As reported elsewhere, the number of patients with a primary trial end point (ICD intervention for VT or ventricular fibrillation) was similar in the two groups. For this analysis, a qualifying event was TdP (on electrocardiogram) or an intracardiac electrogram showing pause-dependent PVT.</AbstractText>A total of 620 electrograms obtained in 131 patients were analyzed blindly by prospectively defined criteria for episodes of pause-dependent polymorphic VT. These were identified in 15/87 (17%) patients receiving dofetilide and 5/87 (6%) patients on placebo (p < 0.05). Five of these episodes were early (<3 days), all of which were TdP on dofetilide. There were 15 late events, 10 on dofetilide and five on placebo (p = 0.29). The median time to a late event was 22 days (range 6 to 107 days) for dofetilide and 99 days (range 34 to 207 days) for placebo.</AbstractText>Pause-dependent PVT was more common among patients receiving dofetilide, although total VT incidence was similar in the two groups. These data suggest that in ICD patients either long-term dofetilide therapy is associated with an increased risk of TdP or the drug alters VT morphology.</AbstractText> |
4,052 | Patients at lower risk of arrhythmia recurrence: a subgroup in whom implantable defibrillators may not offer benefit. Antiarrhythmics Versus Implantable Defibrillator (AVID) Trial Investigators. | The goal of this study was to identify subgroups of arrhythmia patients who do not benefit from use of the implantable cardiac defibrillator (ICD).</AbstractText>Treatment of serious ventricular arrhythmias has evolved toward more common use of the ICD. Since estimates of the cost per year of life saved by ICD therapy vary from $25,000 to perhaps $125,000, it is important to identify patient subgroups that do not benefit from the ICD.</AbstractText>Data for 491 ICD patients enrolled in the Antiarrhythmics Versus Implantable Defibrillators Study were used to create a hazards model relating baseline factors to time to first recurrent arrhythmia. The model was used to predict the hazard for recurrent arrhythmia among all trial patients. A priori cut points provided lower and higher recurrent arrhythmia risk strata. For each stratum the incremental years of life due to ICD versus antiarrhythmic drug therapy were calculated.</AbstractText>Factors that predicted recurrent arrhythmia were: ventricular tachycardia as the index arrhythmia, history of cerebrovascular disease, lower left ventricular ejection fraction, a history of any tachyarrhythmia before the index event and the absence of revascularization after the index event. Survival times (over a follow-up of three years) were identical in each arm of the lowest risk sextile (survival advantage 0.03 +/- 0.12 [se] years), while the survival advantage for patients above the first sextile was 0.27 +/- 0.07 (se) years (two-sided p = 0.05).</AbstractText>Patients presenting with an isolated episode of ventricular fibrillation in the absence of cerebrovascular disease or history of prior arrhythmia who have undergone revascularization or who have moderately preserved left ventricular function (left ventricular ejection fraction > 0.27) are not likely to benefit from ICD therapy compared with amiodarone therapy.</AbstractText> |
4,053 | Predictive value of systolic and diastolic function for incident congestive heart failure in the elderly: the cardiovascular health study. | We sought to assess the ability of echocardiographic indices of systolic and diastolic function to predict incident congestive heart failure (CHF).</AbstractText>Noninvasive indices of subclinical systolic and/or diastolic dysfunction that can be used to identify patients in a transition phase between normal cardiac function and clinical CHF would be valuable. Though midwall shortening and Doppler mitral inflow patterns are seemingly well suited to predict subsequent CHF, the predictive value of these indices has not been investigated.</AbstractText>We studied 2,671 participants in the Cardiovascular Health Study who were free of coronary heart disease, CHF or atrial fibrillation. Clinical and quantitative echocardiographic data were obtained in all participants.</AbstractText>At a mean follow-up of 5.2 years (range 0 to 6 years), 170 participants (6.4% of the cohort) developed CHF. Although 96% of these participants had normal or borderline ejection fraction (EF) at baseline, only 57% had normal or borderline EF at the time of hospitalization. In multivariate modeling, fractional shortening at the endocardium (relative risk [RR] 1.85 per 10-unit decrease, confidence interval [CI] 1.27 to 2.39), fractional shortening at the midwall (RR 1.29 per five-unit decrease, 95% CI 1.11-1.51) and peak Doppler peak E (RR 1.15 for each 0.1 M/s increment; CI 1.02 to 1.21) independently predicted incident CHF. Both high and low Doppler E/A ratios were predictive of incident CHF.</AbstractText>Roughly half the occurrences of CHF in this population are associated with normal or borderline EF. Echocardiographic findings suggestive of subclinical contractile dysfunction and diastolic filling abnormalities are both predictive of subsequent CHF. The standard (FSendo) and refined (FSmw) parameters of systolic function performed similarly in this regard, though subjects with left ventricular hypertrophy and depressed FSmw are at particularly high risk for subsequent CHF.</AbstractText> |
4,054 | Prognostic implications of right atrial ischemic dysfunction in patients with biventricular inferior infarction: transesophageal echocardiographic analysis. | In order to determine the effect of right atrial dysfunction on clinical outcome, six patients with inferior myocardial infarction with extension to right ventricle and right atrium involving only obstructions of the right coronary artery were examined with transesophageal echocardiography (TEE) at the time of the event. Five of the patients were reexamined 15 to 55 months later. Two patients underwent thrombolysis and maintained ratios of right-to-left ventricular diameters of less than 1, as well as normal convexity of the interatrial septum. One patient had spontaneous reperfusion of the right coronary artery, reduction in right ventricular diameter, and normalization of interatrial septum. Another patient underwent delayed angioplasty and manifested a diminished wall movement score (WMS) in the follow-up echocardiogram. One patient died during his first hospitalization with significant right ventricular dilatation, inverted convexity of the interatrial septum, and right atrial thrombosis. The last patient died during follow-up with right ventricular dilatation, increased WMS, right atrial akinesis, and inverted interatrial convexity. Serial TEE examination of patients with infarction of the left ventricular inferior wall is a safe technique for determining the degree of the extension of the ischemic process to the right chambers. |
4,055 | ECG of the month. Shades of evil. Inferolateral myocardial infarction. | The tracings shown below, 12-lead ECG and rhythm strip (lead II), belong to a 74-year-old man, and were recorded on his eighth hospital day. On admission, he gave a history of a "heart attack" about 11 days earlier. |
4,056 | [The best in 2000 on heart stimulation]. | In the last twelve months many important articles have been published in the field of cardiac pacing. The authors analyse 5 of them in this review: the Canadian CTOPP, which compared dual and single chamber pacing in patients with a classical indication for pacing, and concluded that the results were identical in the two modes but not without serious criticism about the validity of this conclusion. A second Canadian trial analysed the effects of atrial stimulation in the prevention of atrial fibrillation but without apparent benefit. In 1999, vaso-vagal syncope had already been studied in a randomised trial; a second one was published in 2000 with concordant results in favour of pacing but reserved for a very selected population. Finally, two articles were devoted to "left heart" pacing in cardiac failure. The MUSTIC trial was the first randomised protocol and its results were favourable for this type of pacing. A physiopathological study reported by a Baltimore group, provided fundamental information: the increase of left ventricular contractility (DP/Dt) occurs without any increase in myocardial oxygen consumption. |
4,057 | [The best in 2000 on echocardiography]. | The advances in Doppler echocardiography, like last year, concern the technology, the indications and the description of the natural history of cardiovascular diseases. The year 2000 will be remembered for the development of portable echocardiographs with two-dimensional and Doppler capabilities but without M mode, pulsed or continuous Doppler. These instruments weigh less than 3 kg and may be used at the bedside; however, problems of training personnel, reimbursement and availability of equipment remain. Myocardial contrast echocardiography has been the subject of many publications which validate continuous intravenous infusion of different contrast agents, which, coupled with techniques of image processing, suggest that quantification of regional myocardial perfusion at rest or during physiological or pharmacological stress may not be far off. The indications of stress echocardiography have increased: in addition to diagnostic and prognostic information in coronary artery disease, the applications of exercise and pharmacological inotropic stress echo extend to asymptomatic valvular regurgitation to detect infraclinical myocardial dysfunction before the usual Doppler echocardiographic parameters show significant changes. The value of Doppler tissue imaging in the assessment of regional myocardial function has been demonstrated: analysis of diastolic function with pulsed Doppler at the mitral annulus, quantification of regional myocardial function in different pathologies such as ischaemic heart disease and cardiomyopathy, validation of indices during stress echocardiography with the hope of a quantitative as well as a qualitative assessment, much improved since the introduction of harmonic imaging. Finally, Doppler haemodynamic evaluation has continued to substitute for cardiac catheterisation, now providing accurate indices of quantification of valvular regurgitation and description of the natural history of cardiac diseases, especially mitral regurgitation irrespective of its cause and aortic stenosis including cases with low output states. The continuing progress of ultrasound technology is therefore confirmed and provides an outlook into the third millennium: development of portable equipment, improved probe technology, use of instruments of quantification and extension of real time three-dimensional reconstruction, systems of image stocking and transmission and better orientation of its usage with the recommendations of scientific societies. |
4,058 | [The best in 2000 on arrhythmia]. | The two major problems of rhythmology in the year 2000 were mainly therapeutic: on the one hand, the treatment of atrial fibrillation and, on the other hand, the treatment of sudden arrhythmic death. These two subjects should not mask the fermentation of ideas, techniques, and diagnostic and therapeutic suggestions which have made up one year of scientific literature in this field. However, simple analysis of the articles published in the leading clinical review, the New England Journal of Medicine, shows that these two subjects are the main items. In the treatment of atrial fibrillation, Canadian investigators in the CTAF study, showed that amiodarone was more effective than Sotalol or Propafenone for the prevention of recurrences of atrial fibrillation in a population of 403 patients followed up for an average of 16 months. There were 35% of recurrences in the amiodarone group compared with 63% in the Sotalol and Propafenone group. Two articles demonstrated the value of automatic external defibrillation in the prevention of sudden arrhythmic death, especially when used in a relatively confined space such as an aeroplane or a casino. These two American Publications showed the value of this approach for a rapid recovery after ventricular fibrillation, the rapidity being the only guarantee of a high survival rate after hospital discharge, about 40% in this series. These various studies should be placed in the perspective of the general changes in treatment of these two pathologies: the treatment of atrial fibrillation is becoming progressively more hybrid, the same patient being considered at different moments for pharmacological antiarrhythmic therapy, ablation or pacing: arrhythmic sudden death is of increasing concern, either with curative treatment by external automatic defibrillation or by preventive therapy with the implantable defibrillator, the trend being towards "prophylactic" indications in patients in whom the high risk of sudden death has been determined. |
4,059 | The nitroderivative of aspirin, NCX 4016, reduces infarct size caused by myocardial ischemia-reperfusion in the anesthetized rat. | NCX 4016, a nitro-ester of aspirin endowed with antithrombotic activity, appears to have clinical potential in treating cardiac complications related to coronary insufficiency. This compound has been shown to improve postischemic ventricular dysfunction and to reduce myocardial infarct size in the rabbit. The cardioprotection conferred by NCX 4016 (10, 30, and 100 mg/kg) and aspirin (ASA, 54 mg/kg) was evaluated in anesthetized rats subjected to 30 min of myocardial ischemia followed by 120 min of reperfusion (MI/R). Drugs were given orally for 5 consecutive days. NCX 4016 displayed remarkable cardioprotection in rats subjected to MI/R as was evident in the reduction of ventricular premature beats and in the incidence of ventricular tachycardia and fibrillation; they were reduced dose dependently and correlated with survival of all rats treated with the higher dose of NCX 4016. In these animals, infarct size was restricted proportionally to the dose of NCX 4016 associated with diminution of both plasma creatine phosphokinase and cardiac myeloperoxidase activities. ASA showed only a minor degree of protection against MI/R damage. Rats treated with N(G)-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg) demonstrated aggravated myocardial damage in terms of arrhythmias, mortality, and infarct size. Supplementation of nitric oxide (NO) with NCX 4016 (100 mg/kg) greatly reduced the worsening effect caused by L-NAME. The beneficial effects of NCX 4016 appear to derive in large part from the NO moiety, which modulates a number of cellular events leading to inflammation, obstruction of the coronary microcirculation, arrhythmias, and myocardial necrosis. |
4,060 | Effects of diaspirin cross-linked hemoglobin (DCLHb) during and post-CPR in swine. | The purpose of the study was to test the hypothesis that diaspirin cross-linked hemoglobin (DCLHb) can produce improved resuscitation during cardiac arrest. DCLHb, a derivative of human hemoglobin, has previously been demonstrated to produce a vasopressor response that is associated with increased blood flow to vital organs. In addition, it is an oxygen carrier. These effects may be beneficial to extreme low flow states, such as that during cardiac arrest and cardiopulmonary resuscitation (CPR). Experimental cardiac arrest and CPR were carried out in 32 anesthetized immature pigs. In each animal, ventricular fibrillation was induced for 5 min, followed by 10 min of standard CPR with a pneumatic device and room air ventilation. High (15 ml/kg) and low (5 ml/kg) doses of DCLHb or equivalent volume of normal saline were infused at the beginning of CPR in a random and blind manner. Cardiac output, organ blood flow, aortic pressure, coronary perfusion pressure, blood gases, and lactate concentrations were obtained before and during CPR. Following the 10-min CPR, the animals were defibrillated and the return of spontaneous circulation (ROSC) determined. DCLHb treatment achieved 75% ROSC compared with 25% in the saline group (p < 0.05). In addition, a better (p < 0.05) myocardial O(2) delivery, venous blood O(2) content, and myocardial and cerebral perfusion pressure were observed in the DCLHb group. DCLHb treatment during cardiac arrest and CPR significantly improves ROSC. This is most likely related to its improvement in coronary perfusion and myocardial oxygen delivery. |
4,061 | [A new dual-chamber defibrillation system: duration, frequency and circadian variation of recurrent supraventricular tachyarrhythmias]. | The treatment of concomitant atrial tachyarrhythmias in patients with malignant ventricular tachyarrhythmias is a major challenge for new defibrillator devices. Atrial fibrillation is not only responsible for inappropriate ventricular therapies, but also reduced left ventricular performance, especially in patients with heart failure and severely depressed left ventricular function. Furthermore, it is a strong risk factor for the development of thromboembolism.</AbstractText>A new dual-chamber implantable defibrillator is capable of tiered atrial therapies for both regular and irregular atrial tachyarrhythmias. In first investigations a high sensitivity and specificity could be shown as well as a promising therapy efficacy of atrial antitachycardia ramp and burst pacing for the treatment of atrial tachycardias. Atrial ramp pacing has shown to be successful for regular atrial tachyarrhythmias in up to 60 to 70% of all episodes. The results have supported a programming of a high first shock energy for treatment of atrial fibrillation. The incidence of atrial fibrillation in patients with a history of atrial fibrillation or without is much higher in the present investigated patient populations than expected.</AbstractText>The more complicated and subtle new dual-chamber detection algorithm has proven to be safe and effective both for the detection of ventricular tachycardia but also in terms of an increase of specificity and a reduction of inappropriate ventricular therapies for atrial tachyarrhythmias.</AbstractText> |
4,062 | [Usefulness of a VDD defibrillation electrode in recording atrial electrograms during atrial flutter and atrial fibrillation]. | Monitoring of atrial signals improves the accuracy in identifying supraventricular tachyarrhythmias to prevent inappropriate therapies in patients with implantable cardioverter-defibrillators (ICD). Since complications due to the additional atrial lead were found in dual chamber ICD systems with 2 leads, we designed a single-pass VDD-lead for use with dual chamber ICDs.</AbstractText>After promising animal experiments in a German multicenter study a prototype VDD lead (single-coil defibrillation electrode with 2 additional fractally coated rings for bipolar sensing in the atrium) was temporarily used in 20 patients. Atrial and ventricular signals were recorded during sinus rhythm, atrial flutter, atrial fibrillation and ventricular tachycardia or ventricular fibrillation. Terminations of ventricular arrhythmias were performed by internal DC shock.</AbstractText>The implantation of the electrode was successful in 18 of 20 patients. Mean atrial pacing threshold was 2.45 +/- 0.9 V/0.5 ms, mean atrial impedance was 215 +/- 31 Ohm. Atrial amplitudes were greater during sinus rhythm (2.7 +/- 1.6 mV) than during atrial flutter (1.36 +/- 0.28 mV, p < 0.05) or atrial fibrillation (0.92 +/- 0.29 mV, p < 0.01). During ventricular fibrillation atrial "sinus"-signals had significantly (p < 0.01) lower amplitudes than during sinus rhythm. Mean ventricular sensing was 13.3 +/- 7.9 mV, mean ventricular impedance was 577 +/- 64 Ohm. Defibrillation was successful with 20 J shock. 99.6% of P waves could be detected in sinus rhythm and 85 +/- 9.9% of flutter waves during atrial flutter. During atrial fibrillation 55% of atrial signals could be detected without modification of the signal amplifier.</AbstractText>A new designed VDD dual chamber electrode provides stable detection of atrial and ventricular signals during sinus rhythm and atrial flutter. For reliable detection of atrial fibrillation modifications of the signal amplifier are necessary.</AbstractText> |
4,063 | [Mode-switching algorithms: programming and usefulness]. | Automatic mode switching is defined as the ability of a pacemaker to reprogram itself from tracking to non-tracking mode in response to atrial tachyarrhythmias, and to regain tracking mode as soon as the tachyarrhythmia terminates. In contrast to upper rate behavior, mode switching does not only limit atrial tracking at a certain rate but actively drives the ventricular pacing rate back to lower rate or sensor rate as long as the atrial tachyarrhythmia persists. In contrast to DDD with mode switch, AV synchrony may be lost in DDIR mode if the sinus rate exceeds the sensor rate. DDD pacing with mode switching represents a valuable option in patients with AV block and paroxysmal atrial tachyarrhythmias. It may prevent the transition from paroxysmal to permanent atrial fibrillation after AV node ablation to a higher extent than VVI(R) pacing. On the other hand, patients with sinus node disease and normal AV conduction may benefit from DDIR mode with long AV interval. Mode switching should provide a rapid, sensitive and specific detection of atrial tachyarrhythmias, fast switch to non-tracking mode without ventricular pacing at the upper rate limit, adequate ventricular rate during the atrial tachyarrhythmia, rapid, sensitive and specific detection of conversion to sinus rhythm and fast switch back to tracking mode. In addition, oscillations between DDD and DDI mode with sudden ventricular rate changes should be avoided. MODE-SWITCHING ALGORITHMS: To achieve these aims, different mode-switching algorithms have been developed which all show specific disadvantages: reliable but slow response to atrial tachyarrhythmias, fast but unspecific switch to non-tracking mode, mode oscillations, inclination to inadequate mode-switching due to ventricular far-field sensing, failure to perform modeswitching during atrial flutter or intermittent atrial undersensing. Some of these problems can be avoided by careful atrial lead implantation providing atrial signals above 2 mV and avoiding ventricular far-field signals. Programming of mode-switching related parameters (e.g. atrial rate and number of fast beats required for mode switch), atrial blanking times, and atrial sensitivity can solve some of the problems with mode switching. Clinical results show a strong influence of device programming and atrial undersensing on mode-switching performance. Some data suggest a superiority of fast mode-switching algorithms with regard to clinical symptoms. However, loss of AV synchrony during sinus rhythm due to premature or inadequate mode switching may limit the benefit of fast mode switching.</AbstractText>Improved performance may be achieved by a combination of different mode-switching algorithms (e.g. one algorithm for detection of atrial fibrillation, another one for detection of atrial flutter). In addition, programmability of several algorithms (e.g. mean atrial rate, beat-to-beat, x out of y) within the same device and atrial cycle-dependent sensitivity adjustment similar to automatic gain control in implantable defibrillators may further increase the clinical use of automatic mode switching.</AbstractText> |
4,064 | Lidocaine and surgical modification reduces mortality in a rat model of cardiac failure induced by coronary artery ligation. | Coronary artery ligation in the rat provides a useful experimental model of cardiac failure; however, this procedure carries with it a high mortality rate (50%). In this study, we used lidocaine (10 mg/kg, i.m.) before coronary artery ligation and 2 h after surgery to minimise the incidence of ventricular fibrillation (VF) that leads to sudden death in this model. We found that coronary artery ligation, using lidocaine in conjunction with a modified surgical procedure, had a mortality rate of 15%, much lower than reported in previous studies using this model. These modifications allow for the production of larger infarcts with 29% of animals having an infarct size > 50% of the epicardial surface. Infarct size in our myocardial infarction (MI) group varied between 5% and 75% of the left ventricular (LV) surface area resulting in a mean infarct size of 41.3 +/- 1.3% for the epicardial surface and 40.0 +/- 1.3% for the endocardial surface. |
4,065 | Symptomatic atrial arrhythmias in hemodialysis patients. | <AbstractText Label="BACKGROUND/AIMS" NlmCategory="OBJECTIVE">Cardiac arrhythmias are frequent in hemodialysis patients and can interrupt treatment. However, the frequency and risk factors have remained unclear because previous reports of arrhythmias in dialysis patients have usually been continuous-monitoring studies that looked at all cardiac ectopy regardless of its seriousness.</AbstractText>We reviewed retrospectively only symptomatic atrial arrhythmias in a population of 106 maintenance hemodialysis patients over three years, in order to estimate their actual frequency and any risk factors.</AbstractText>Ten patients, seven men and three women, required treatment for atrial arrhythmias (9.4%): four for supraventricular tachycardia, three for atrial flutter, and three for atrial fibrillation. Their mean age was 53.7 +/- 6.1 years; five of them were < or = 40 years. Seven arrhythmias were new, three were recurrences. All but one occurred between 3 and 4 hours of hemodialysis, and dialysis had to be stopped in nine instances. There was no pattern of hypotensive episodes preceding the arrhythmias. Mean serum K+ drawn at the time of the arrhythmias was 3.8 +/- 0.2 mEq/L. Mean plasma intact parathormone was 1128 +/- 417 pg/mL, compared to 454 +/- 58 pg/mL for our entire hemodialysis population (p = .0036). Subsequent echocardiograms showed abnormalities in 9/10 patients: five had left ventricular hypertrophy, six had left atrial enlargement, five had valvular lesions (four mitral regurgitation; one aortic incompetence), and three had ejection fractions <50%. There were four deaths in these patients over the next 14 months, but probably only one was cardiac.</AbstractText>Serious atrial arrhythmias are common in a hemodialysis population. Risk factors for symptomatic atrial arrhythmias in hemodialysis patients may include hyperparathyroidism and echocardiographic findings of chamber enlargement, valvular lesions, or ventricular dysfunction.</AbstractText> |
4,066 | [How I treat...persistent atrial fibrillation, by internal cardioversion, in a patient with exreme obesity]. | An ethylic hypertensive patient with a BMI of 51.4 developed persistent atrial fibrillation with high ventricular rates. External electrical cardioversion was attempted, but failed in spite of high energy shocks (350 joules). Sinus rhythm was restored by internal cardioversion (12 joules). The value and indications of the techniques are briefly discussed. |
4,067 | Spontaneous conversion to sinus rhythm of recent (within 24 hours) atrial fibrillation. | The purpose of the study was to determine the likelihood of spontaneous conversion of recent onset (< 24 hr) paroxysmal atrial fibrillation (Af) to sinus rhythm and to define clinical and echocardiographic characteristics which may predict it.</AbstractText>One hundred fifty-three consecutive adult patients admitted to the hospital with recent onset Af (< 24 hr) were studied. In each patient history, complete physical examination, 12-lead electrocardiogram, chest X-ray, routine hematological studies, serum electrolytes, troponin, thyroid function studies and a complete echocardiographic evaluation were performed. Patients hemodynamically unstable, with recent myocardial infarction, unstable angina, average ventricular rate > 150 beats/min, hyperthyroidism, congestive heart failure, left ventricular hypertrophy, valvular heart disease, and on antiarrhythmic drugs at the time of admission, were excluded. Patients were monitored without antiarrhythmic therapy for at least 24 hr from the onset of Af.</AbstractText>Spontaneous conversion to sinus rhythm occurred in 109 patients (71.2%); among patients with spontaneous conversion 73.4% converted in the first 12 hr. Age, gender, other clinical characteristics, left ventricular dimensions and performance did not separate patients with or without spontaneous conversion. Left atrial size was significantly greater in patients without compared to patients with spontaneous conversion (p < 0.03); likewise increased left atrial size (> 40 mm) was seen more often in patients without compared to patients with spontaneous conversion (45% vs 22%, p < 0.05).</AbstractText>Spontaneous conversion to sinus rhythm occurred in 71% of patients with recent onset (< 24 hr) Af. Left atrial size was the only predictor of spontaneous conversion in this highly selected group of patients.</AbstractText> |
4,068 | Warfarin therapy for an octogenarian who has atrial fibrillation. | In North America, atrial fibrillation is associated with at least 75 000 ischemic strokes each year. Most of these strokes occur in patients older than 75 years of age. The high incidence of stroke in very elderly persons reflects the increasing prevalence of atrial fibrillation that occurs with advanced age, the high incidence of stroke in elderly patients, and the failure of physicians to prescribe antithrombotic therapy in most of these patients. This failure is related to the increased risk for major hemorrhage with advanced age, obfuscating the decision to institute stroke prophylaxis with antithrombotic therapy. This case-based review describes the risk and benefits of prescribing antithrombotic therapy for a hypothetical 80-year-old man who has atrial fibrillation and hypertension, and it offers practical advice on managing warfarin therapy. After concluding that the benefits of warfarin outweigh its risks in this patient, we describe how to initiate warfarin therapy cautiously and how to monitor and dose the drug. We then review five recent randomized, controlled trials that document the increased risk for stroke when an international normalized ratio (INR) of less than 2.0 is targeted among patients with atrial fibrillation. Next, we make the case that cardioversion is not needed for this asymptomatic patient with chronic atrial fibrillation. Instead, we choose to leave the patient in atrial fibrillation and to control his ventricular rate with atenolol. Later, when the INR increases to 4.9, we advocate withholding one dose of warfarin and repeating the INR test. Finally, when the patient develops dental pain, we review the analgesic agents that are safe to take with warfarin and explain why warfarin therapy does not have to be interrupted during a subsequent dental extraction. |
4,069 | The defibrillation system of basic emergency medical technicians in Japan: a comparison with other systems from a 14-year review of out-of-hospital cardiac arrest reports. | Although seven years have passed after basic emergency medical technician (EMT) defibrillation system was introduced in Japan, the overall survival for out-of-hospital cardiac arrest (OHCA) remains poor. We investigated factors leading to such an unanticipated result in Japan by comparing the data of OHCA in Japan with those in other countries. We obtained population-based OHCA data from three communities in Japan. We also performed a comprehensive literature and manual search to identify reports that included rates for incidence and survival or provided sufficient data for the calculation of these rates of OHCA. Statistical analysis was performed to compare survival and incidence rates between the communities. We identified 36 articles from 16 countries by a comprehensive literature search. There was no significant difference in incidence and survival rates among communities in Japan. Although the incidence rate of collapse-witnessed OHCA with ventricular fibrillation (VF) was much lower in Japan than western countries, the proportions of survival from it were comparable to those. Basic-EMT defibrillation system in Japan has yielded excellent result in terms of the survival of VF cases. However, much lower proportion of VF to all cases is responsible for lower overall rates of survival from OHCA in Japan. |
4,070 | Bias of QT dispersion. | Prolonged QT dispersion (QTD) is associated with an increased risk of arrhythmic death but its accuracy varies substantially between otherwise similar studies. This study describes a new type of bias that can explain some of these differences.</AbstractText>One dataset (DiaSet) consisted of 356 subjects: 169 with diabetes, 187 nondiabetic control persons. Another dataset (ArrSet) consisted of 110 subjects with remote myocardial infarction: 55 with no history of arrhythmia and 55 with a recent history of ventricular tachycardia or fibrillation.</AbstractText>12-lead surface ECGs were recorded with an amplification of 10 mm/mV at a paper speed of 50 mm/s. The QT interval was measured manually by the tangent-method. The bias depends on the magnitude of the measurement errors and the measurable part of the bias increases with the number of the repeated measurements of QT.</AbstractText>The measurable bias was significant for both datasets and decreased for increasing QTD in the DiaSet (P < 0.001) and in the ArrSet (P = 0.11). The bias was 2.5 ms and 1.9 ms at QTD = 38 ms and 68 ms, respectively, in the ArrSet, and 7.5 ms and 2.8 ms at QTD = 19 ms and 55 ms, respectively, in the DiaSet.</AbstractText>This study shows that random measurement errors of QT introduces a type of bias in QTD that decreases as the dispersion increases, thus reducing the separation between patients with low versus high dispersion. The bias can also explain some of the differences in the mean QTD between studies of healthy populations. Averaging QT over three successive beats reduces the bias efficiently.</AbstractText> |
4,071 | Relation of ventricular fibrillation threshold to heart rate during normal ventilation and hypoventilation in female Wistar rats: a chronophysiological study. | The aim of our study was to verify the relationship between heart rate (HR) and ventricular fibrillation threshold (VFT) during different types of ventilation in female Wistar rats from the circadian point of view. The experiments were performed under pentobarbital anesthesia (40 mg/kg i.p., adaptation to a light-dark cycle 12:12 h, open chest experiments) and the obtained results were averaged independently of the seasons. The VFT measurements were performed during normal ventilation (17 animals) and hypoventilation (10 animals). The HR was recorded immediately before the rise of ventricular arrhythmias. Results are expressed as arithmetic means -/+ S.D. and differences are considered significant when p<0.05. The basic periodic characteristics were calculated using single and population mean cosinor tests. The results from our experiments have demonstrate that 1) the VFT and HR respond identically to hypoventilation by a decrease in the light and also in the dark phases, and 2) hypoventilation changes the 24-h course of the VFT without a change in the 24-h rhythm of the HR. It is concluded that the HR and VFT behave as two independent functional systems without apparent significant circadian dependence during both types of ventilation. |
4,072 | Prognostic value of an abnormal signal-averaged electrocardiogram in patients with nonischemic dilated cardiomyopathy. | The usefulness of an abnormal signal-averaged ECG (SAECG) for the risk stratification of patients with dilated cardiomyopathy was studied prospectively in 76 patients. Multiple analysis showed that an abnormal SAECG predicted cardiac mortality (p = 0.0046), sudden cardiac death, and the need for resuscitation (p = 0.003); however, it did not predict death from heart failure and heart transplantation. |
4,073 | The distribution of refractory periods influences the dynamics of ventricular fibrillation. | The spatial and dynamic properties of ventricular fibrillation (VF) may be random or related to cellular electrical properties of the normal heart. Local activation intervals (AIs) in VF may depend on the local refractory period (RP), and sustained VF may require a steep action potential (AP) restitution curve. In guinea pig hearts, AP durations (APDs) and RPs on the epicardium are shorter at the apex and progressively longer toward the base, producing gradients of RPs that may influence the spatial organization of VF. In the present study, the influence of APDs on VF dynamics is investigated in perfused guinea pig hearts stained with a voltage-sensitive dye by comparing APD gradients to the dynamics of VF elicited by burst pacing. In VF, AIs had no clear periodicity, but average AIs were shorter at the apex (57.5+/-8.1 ms) than the base (76.1+/-1.5 ms, n=6, P<0.05) and had gradients similar to APD gradients (correlation coefficient 0.71+/-0.04). Analysis of local velocity vectors showed no preferential directions, and fast Fourier transform (FFT) power spectra were broad (10 to 24 Hz) with multiple peaks (n=6). However, the selective inhibition of delayed K(+) rectifying currents, I(Kr) (E4031; 0.5 micromol/L, n=3), shifted FFT spectra from complex to a lower dominant frequency (10 Hz) and altered repolarization but retained the correlation between mean AIs and RPs. Thus, VF dynamics are consistent with a multiple wave-make and wave-break mechanism, and the local RP influences VF dynamics by limiting the range of VF frequencies and AIs at each site. The full text of this article is available at http://www.circresaha.org. |
4,074 | Case report: adenosine induced ventricular fibrillation in a patient with stable ventricular tachycardia. | Adenosine is frequently used in emergency departments and intensive care units for the termination of narrow complex tachycardias. Recently its utility in terminating wide complex tachycardias has been reported in the literature. Adenosine is generally felt to be a safe medication even though its proarrhythmic effects in the setting of narrow complex or supraventricular tachycardias have been well documented. Herein, we describe the first case to our knowledge of adenosine inducing ventricular fibrillation in a patient with a stable wide complex tachycardia that was subsequently proven to be ventricular tachycardia at electrophysiologic study. |
4,075 | Effect of different location of atrial lead position on nearfield and farfield electrograms in dual chamber pacemaker-defibrillators. | The normal functioning of dual chamber pacemaker-cardioverter defibrillator (AV pacer/ICD) may be affected by oversensing of the farfield R wave (FFRW) by the atrial channel. This study aimed to investigate whether placement of the AV pacer/ICD's atrial lead at a lateral (LAT) wall location compared to a medial (MED) location i.e. the appendage of the right atrium, would reduce the amplitude of FFRWs but not the nearfield atrial electrograms (AEGMs) during sinus rhythm (SR) and ventricular fibrillation (VF). In 17 patients, real time electrograms were recorded during SR and induced VF through the atrial lead initially at the MED and subsequently at the LAT location. In 10 patients the electrograms in SR were also recorded on a computerized data acquisition and recording system at different band-pass filter settings. Although FFRWs were recorded both at MED and LAT locations, they were much smaller, 3.5+/-4.1mm during SR and 1.7+/-2.2mm during VF at the LAT location. At 30-500Hz band-pass filter, lower amplitudes of FFRWs 0.14+/-0.09 mV were recorded at the LAT location. The V/A ratios of the amplitudes of FFRWs and AEGMs were smaller at the LAT location during SR and VF. The nearfield AEGMs were of similar amplitudes at the MED and LAT locations. These data indicate that lower amplitudes of FFRWs are recorded by placement of the atrial lead at the lateral wall of the right atrium. Oversensing of FFRWs may be prevented to improve functioning of the AV pacer-ICD. |
4,076 | Effects of simulated ischemia on spiral wave stability. | Regional hyperkalemia during acute myocardial ischemia is a major factor promoting electrophysiological abnormalities leading to ventricular fibrillation (VF). However, steep action potential duration restitution, recently proposed to be a major determinant of VF, is typically decreased rather than increased by hyperkalemia and acute ischemia. To investigate this apparent contradiction, we simulated the effects of regional hyperkalemia and other ischemic components (anoxia and acidosis) on the stability of spiral wave reentry in simulated two-dimensional cardiac tissue by use of the Luo-Rudy ventricular action potential model. We found that the hyperkalemic "ischemic" area promotes wavebreak in the surrounding normal tissue by accelerating the rate of spiral wave reentry, even after the depolarized ischemic area itself has become unexcitable. Furthermore, wavebreak and fibrillation can be prevented if the dynamical instability of the normal tissue is reduced significantly by targeting electrical restitution properties, suggesting a novel therapeutic approach. |
4,077 | Doppler echocardiography reliably predicts pulmonary artery wedge pressure in patients with chronic heart failure even when atrial fibrillation is present. | In patients with chronic congestive heart failure a high pulmonary artery wedge pressure (PAWP) is associated with poor prognosis, severe symptoms and low exercise tolerance. When atrial fibrillation is present the non-invasive prediction of PAWP by Doppler echocardiography is generally considered to be not reliable.</AbstractText>In 51 consecutive patients with chronic heart failure, due to either ischemic and non-ischemic dilated cardiomyopathy, and atrial fibrillation simultaneous Doppler echocardiographic and hemodynamic studies were used to estimate PAWP. The power of the obtained multivariate equation was compared with that of previously developed equations and was then prospectively tested in a group of 15 patients.</AbstractText>The deceleration rate (DR) of early diastolic mitral flow, the left ventricular iso-volumic relaxation time (IVRT) and the systolic fraction of pulmonary venous flow (SF) were independent predictors of PAWP and the following multivariable equation was derived: PAWP=24.04 + 1.23 x DR- 0.089 x IVRT - 0.175 x SF. The correlation between invasive PAWP and the PAWP non-invasively estimated by this equation in the testing group was 0.91 (standard error of estimate=3.2 mmHg). The mean difference was 0.93 and the standard error of differences was 2.7 mmHg.</AbstractText>In patients with chronic heart failure due to dilated cardiomyopathy who are in atrial fibrillation a relatively accurate estimation of PAWP can be obtained by Doppler echocardiography of mitral and pulmonary venous flow.</AbstractText> |
4,078 | Improvement of defibrillation efficacy and quantification of activation patterns during ventricular fibrillation in a canine heart failure model. | Little is known about the effects of heart failure (HF) on the defibrillation threshold (DFT) and the characteristics of activation during ventricular fibrillation (VF).</AbstractText>HF was induced by rapid right ventricular (RV) pacing for at least 3 weeks in 6 dogs. Another 6 dogs served as controls. Catheter defibrillation electrodes were placed in the RV apex, the superior vena cava, and the great cardiac vein (CV). An active can coupled to the superior vena cava electrode served as the return for the RV and CV electrodes. DFTs were determined before and during HF for a shock through the RV electrode with and without a smaller auxiliary shock through the CV electrode. VF activation patterns were recorded in HF and control animals from 21x24 unipolar electrodes spaced 2 mm apart on the ventricular epicardium. Using these recordings, we computed a number of quantitative VF descriptors. DFT was unchanged in the control dogs. DFT energy was increased 79% and 180% (with and without auxiliary shock, respectively) in HF compared with control dogs. During but not before HF, DFT energy was significantly lowered (21%) by addition of the auxiliary shock. The VF descriptors revealed marked VF differences between HF and control dogs. The differences suggest decreased excitability and an increased refractory period during HF. Most, but not all, descriptors indicate that VF was less complex during HF, suggesting that VF complexity is multifactorial and cannot be expressed by a scalar quantity.</AbstractText>HF increases the DFT. This is partially reversed by an auxiliary shock. HF markedly changes VF activation patterns.</AbstractText> |
4,079 | Increased wave break during ventricular fibrillation in the epicardial border zone of hearts with healed myocardial infarction. | The action potential duration (APD) restitution hypothesis of wave break during ventricular fibrillation (VF) in the epicardial border zone (EBZ) of hearts with chronic myocardial infarction is unknown.</AbstractText>VF was induced by rapid pacing, and the EBZ with the two adjoining sites (right ventricle and lateral left ventricle) were sequentially mapped in random order in 7 open-chest anesthetized dogs 6 to 8 weeks after left anterior descending artery occlusion and in 4 control dogs. At each site, 3 seconds of VF was mapped with 477 bipolar electrodes 1.6 mm apart. The number of wave fronts and approximate entropy were significantly (P:<0.01) higher in the EBZ than all other sites in both groups independent of the rate of invasion of new wave fronts and epicardial breakthroughs. The higher wavelet density in the EBZ was caused by increased (P:<0.01) incidence of spontaneous wave breaks. There was no difference between the two groups in either reentry period (80 episodes) or VF cycle length. Reentry in the EBZ had a smaller core perimeter, slower rotational speed, and a small or no excitable gap (P:<0.01), often causing termination after one rotation. The dynamic monophasic action potential duration restitution curve in the EBZ had longer (P:<0.01) diastolic intervals, over which the slope was >1. Connexin43-positive staining was significantly (P:<0.01) and selectively reduced in the EBZ.</AbstractText>A selective increase in wave break and alteration of reentry occur in the EBZ during VF in hearts with healed myocardial infarction. Increased wave break in the EBZ is compatible with the action potential duration restitution hypothesis.</AbstractText> |
4,080 | Cost-effectiveness of the implantable cardioverter-defibrillator: results from the Canadian Implantable Defibrillator Study (CIDS). | In the Canadian Implantable Defibrillator Study (CIDS), we assessed the cost-effectiveness of the implantable cardioverter-defibrillator (ICD) in reducing the risk of death in survivors of previous ventricular tachycardia (VT) or fibrillation (VF).</AbstractText>Healthcare resource use was collected prospectively on the first 430 patients enrolled in CIDS (n=212 ICD, n=218 amiodarone). Mean cost per patient, adjusted for censoring, was computed for each group based on initial therapy assignment. Incremental cost-effectiveness of ICD therapy was computed as the ratio of the difference in cost (ICD minus amiodarone) to the difference in life expectancy (both discounted at 3% per year). All costs are in 1999 Canadian dollars (C$1 approximately US$0.65). Over 6.3 years, mean cost per patient in the ICD group was C$87 715 versus C$38 600 in the amiodarone group (difference C$49 115; 95% CI C$25 502 to C$69 508). Life expectancy for the ICD group was 4.58 years versus 4.35 years for amiodarone (difference 0.23, 95% CI -0.09 to 0.55), for incremental cost-effectiveness of ICD therapy of C$213 543 per life-year gained. ICD benefit was greater in patients with low left ventricular ejection fraction (<35%), and cost-effectiveness in this group was more attractive (C$108 484). Alternative extrapolations of survival benefit and costs to 12 years indicated cost-effectiveness in the range of C$100 000 to C$150 000 per life-year gained.</AbstractText>At C$213 543, the value for the money offered by ICD therapy is not attractive by currently accepted standards. Further research is warranted to identify the indications and patient subgroups for whom ICDs are a cost-effective use of resources.</AbstractText> |
4,081 | Acute heart failure after allogeneic blood stem cell transplantation due to massive myocardial infiltration by cytotoxic T cells of donor origin. | A 17-year-old male with AML FAB M4 relapsed 4 months after myeloablative conditioning and peripheral blood stem cell transplantation (PBSCT) from an HLA-identical unrelated donor. A second PBSC harvest was infused 2 days after completion of cytoreductive therapy with mitoxantrone 7 mg/m(2)/day i.v. for 3 days (total dose 21 mg/m(2)), fludarabine 30 mg/m(2)/day i.v. for 6 days (total dose 180 mg/m(2)) and Ara-C 125 mg/m(2)/day i.v. for 5 days (total dose 625 mg/m(2)). Neutrophil recovery occurred on day +10 and was associated with GVHD grade III of the skin which was treated with cyclosporin A (CsA) and prednisone. Because of fever of unknown origin and progressive fatigue combined with hypotension on day +15 after second PBSCT, echocardiography was performed which revealed a dramatic decrease in systolic function compared to the status pre-transplant. On the same day acute heart failure with consecutive ventricular fibrillation occurred. Although resuscitation was performed immediately the patient died. The autopsy revealed massive infiltration by donor CD8-positive lymphocytes with concomitant extensive damage of the heart tissue. Acute myocarditis of viral origin was excluded by in situ hybridization and nested PCR techniques. In this patient, myocardial involvement by acute GVHD seems to have triggered a fatal arrhythmia and heart failure. |
4,082 | Restoration of normal ventricular electrophysiology in renovascular hypertensive rabbits after treatment with losartan. | Left ventricular hypertrophy (LVH) is associated with abnormal ventricular electrophysiology. We have shown complete regression of LVH and normalization of ventricular electrophysiology in renovascular hypertensive rabbits treated with captopril. To determine if angiotensin II type 1 receptor (AT1) blockade produces the same benefit, we treated hypertensive rabbits with losartan for 3 months. LVH was evaluated by heart-to-body weight ratio (HW/BW). Vulnerability to ventricular arrhythmia was assessed by ventricular fibrillation threshold (VFT) and dispersion of effective refractory period (ERP). The electrical properties of single left ventricular myocytes were characterized by action potential duration at 90% repolarization (APD90) and inward rectifier K+ current (I(K1)) density. Hypertensive rabbits treated with vehicle (LVH/Vehicle) had higher mean arterial pressure (MAP, 81+/-2 vs. 60+/-2 mm Hg) and HW/BW (2.71+/-0.07 vs. 1.97+/-0.04 g/kg), lower VFT (20+/-1 vs. 39+/-2 mA), larger dispersion of ERP (34+/-3 vs. 14+/-3 ms), longer APD90 (187+/-6 vs. 162+/-6 ms) and lower I(K1) density compared with control rabbits. Hypertensive rabbits treated with losartan (LVH/Losartan) had HW/BW (2.36+/-0.06 g/kg) between those of LVH/Vehicle and control rabbits, whereas MAP (65+/-2 mm Hg), VFT (34+/-2 mA), dispersion of ERP (19+/-1 ms), APD90 (160+/-6 ms), and I(K1) density were significantly different from LVH/Vehicle but similar to control. We conclude that AT1 blockade in renovascular hypertensive rabbits normalizes ventricular electrophysiology. |
4,083 | Does acute-phase beta blockade reduce left atrial appendage function in patients with chronic nonvalvular atrial fibrillation? | To investigate whether acute-phase beta-blocker therapy has a harmful effect on left atrial appendage (LAA) function in patients with chronic nonvalvular atrial fibrillation by transesophageal echocardiography (TEE), we evaluated 21 patients with normal left ventricular systolic function and a poorly controlled ventricular rate, despite the use of digoxin. Baseline parameters that were obtained included heart rate, blood pressure, LAA emptying velocities, and left atrial spontaneous echo contrast intensity. Then, each patient was given a bolus dose of 5 mg metoprolol. Ten minutes later, a second set of assessments was performed. After the first TEE studies, each patient began treatment with metoprolol (50 mg orally twice daily for 1 week). A second TEE study was performed after 1 week of continuous oral metoprolol therapy at maintenance dose, and values were again determined. The average resting apical heart rate was 91 +/- 7 bpm. As expected, beta-blocker therapy showed a marked decrease in heart rate at 10 minutes (79 +/- 6 bpm, P <.001) and at 1 week (71 +/- 4 bpm, P <.001). Beta-blocker therapy caused a significant reduction in systolic and diastolic blood pressures (144 +/- 16 / 93 +/- 6 mm Hg at baseline, 137 +/- 16 / 87 +/- 9 mm Hg at 10 minutes, and 135 +/- 12 / 86 +/- 8 mm Hg at 1 week, P <.001). With the beta-blocker therapy, the baseline transesophageal Doppler parameter of LAA emptying velocities (at baseline 24 +/- 7 cm/s) fell significantly at 10 minutes (19 +/- 7 cm/s, P <.001) and at 1 week (17 +/- 6 cm/s, P <.001) after initiation of beta-blocker therapy. After a bolus of metoprolol, spontaneous echo contrast intensity did not change in any patients, but 1 week later, it increased in 1 patient. In 2 patients who had not been found to have an LAA thrombus at baseline TEE study, the second TEE examination demonstrated new thrombi in the LAA. In conclusion, our findings suggest that in patients with chronic nonvalvular atrial fibrillation who have normal left ventricular systolic function and a poorly controlled ventricular rate despite the use of digoxin, acute-phase beta blockade may have a harmful effect on LAA function. |
4,084 | A placebo controlled evaluation of the antifibrillatory effects of carvedilol. | This article evaluates the antifibrillatory effects of carvedilol 5 mg/kg and vehicle (dimethyl-formamide) over time. Sprague-Dawley rats were anesthetized and intubated. They underwent baseline ventricular fibrillation threshold (VFT) determination and then received 1 of the 2 treatments (n = 10/group) over 8 minutes. VFT and determinations were performed at 2, 7, 15, 30, 45, and 60 minutes postinfusion. Carvedilol significantly increased the VFT at 2, 7, 15, 30 minutes versus baseline and the vehicle control group. Carvedilol significantly reduced the heart rate and the mean arterial pressure at every evaluable time point versus baseline and vehicle control. Carvedilol showed significant antifibrillatory effects versus baseline and vehicle for the first 30 minutes but not thereafter, even though the heart rate and mean arterial pressure remain significantly reduced. |
4,085 | Effects of implantable cardioverter defibrillator implantation and shock application on biochemical markers of myocardial damage. | Implantable cardioverter defibrillator (ICD) implantation is a common approach in patients at high risk of sudden cardiac death. To check for normal function, it is necessary to test the ICD. For this purpose, repetitive induction and termination of ventricular fibrillation by direct current shocks is required. This may lead to minor myocardial damage. Cardiac troponin T (cTnT) and I (cTnI) are specific markers for the detection of myocardial injury. Because these proteins usually are undetectable in healthy individuals, they are excellent markers for detecting minimal myocardial damage. The objective of this study was to evaluate the effect of defibrillation of induced ventricular fibrillation on markers of myocardial damage.</AbstractText>This study included 14 patients who underwent ICD implantation and intraoperative testing. We measured cTnT, cTnI, creatine kinase MB (CK-MB) mass, CK activity, and myoglobin before and at definite times after intraoperative shock application.</AbstractText>Depending on the effectiveness of shocks and the energy applied, the cardiac-specific markers cTnT and cTnI, as well as CK-MB mass, showed a significant increase compared with the baseline value before testing and peaked for the most part 4 h after shock application. In contrast, the increases in CK activity and myoglobin were predominantly detectable in patients who received additional external shocks.</AbstractText>ICD implantation and testing leads to a short release of cardiac markers into the circulation. This release seems to be of cytoplasmic origin and depends on the number and effectiveness of the shocks applied.</AbstractText> |
4,086 | Does early repolarization in the athlete have analogies with the Brugada syndrome? | To re-examine the prevalence and presentation of early repolarization in athletes and to compare it with electrocardiographic abnormalities observed in patients with the Brugada syndrome.</AbstractText>Electrocardiograms of 155 male athletes and 50 sedentary controls were studied. Early repolarization was considered present if at least two adjacent precordial leads showed elevation of the ST segment > or =1 mm. Amplitude and morphology of ST elevation, the leads where it was present and the lead in which it showed its maximum value were analysed together with QRS duration, the presence of right ventricular activation delay, QT and QTc duration. Data were compared with those obtained by electrocardiograms of 23 patients with the Brugada syndrome.</AbstractText>Early repolarization was found in 139 athletes (89%) and 18 controls (36%, P< or =0.025), being limited to right precordial leads in 42 (30%) athletes and 13 (72%) controls (P< or =0.001). Only 12 (8.6%) athletes and one control (5.5%) with early repolarization had an ST elevation 'convex toward the top' in right precordial leads, similar to that seen in the Brugada syndrome. In athletes the maximum ST elevation was greater (2.3+/-0.6 mm) than in the controls (1.2+/-0.8 mm; P< or =0.004) but significantly lower than in patients with the Brugada syndrome (4.4+/-0.7 mm; P< or =0.0001). Patients with the Brugada syndrome also had a greater QRS duration (0.11+/-0.02 s) than athletes (0.090+/-0.011 s; P< or =0.0001) with early repolarization.</AbstractText>Early repolarization is almost always the rule in athletes but it is also frequent in sedentary males. Tracings somewhat simulating the Brugada syndrome were observed in only 8% of athletes without a history of syncope or familial sudden death. Significant differences exist between athletes with early repolarization and patients with the Brugada syndrome as regards the amplitude of ST elevation and QRS duration.</AbstractText> |
4,087 | [Symptoms of primary endocardial fibroelastosis in a young adult]. | A 21-year-old woman with known endocardial fibroelastosis diagnosed when aged 3 months was admitted because of progressive dyspnoea. The physical examination revealed symptoms of heart failure, with pulmonary rales, mild hepatomegaly, and tachyarrhythmia.</AbstractText>The electrocardiogram showed atrial fibrillation, complete right bundle branch block and right ventricular hypertrophy. Echocardiography indicated hypertrophy and dilatation of the right ventricle (61 mm) with tricuspid regurgitation and hypoplasia of the left ventricle. Heart catheterization confirmed pulmonary hypertension (60/46 mmHg) as well as dilatation and hypokinesia of the right ventricle. Right ventricular biopsy showed severe myocardial hypertrophy resulting from secondary pulmonary hypertension, while no evidence of myocarditis or idiopathic dilated cardiomyopathy was found.</AbstractText>Symptoms of heart failure improved under medical treatment with digitalis, angiotensin-converting enzyme inhibitor and diuretics.</AbstractText>Primary endocardial fibroelastosis of the contracted type must be included in the differential diagnosis of heart failure occurring in young adults.</AbstractText> |
4,088 | [Study of combined anticoagulant (fluindione)-aspirin therapy in patients with atrial fibrillation at high risk for thromboembolic complications. A randomized trial (FFAACS)]. | A combination of low-dose aspirin (A) and anticoagulation (AC) may provide better protection against thromboembolic events compared with AC alone in high-risk patients with atrial fibrillation (AF).</AbstractText>We performed a multicentric placebo-controlled double blind-trial to test the preventive efficacy against thromboembolic events of the addition of aspirin (A) (100 mg) or placebo (P) to anticoagulant treatment in patients with high-risk atrial fibrillation. A total of 157 patients were included, with atrial fibrillation and previous thromboembolic event or older than 65 years with either a history of hypertension, a recent episode of heart failure or a left ventricular dysfunction. All patients received fluindione (F) and P or F and A, with an INR target between 2 and 2.6. The primary endpoint was a combined endpoint of stroke (ischaemic or haemorrhagic), myocardial infarction, systemic arterial emboli or vascular death.</AbstractText>The study had to be stopped prematurely owing to a too low recruitment rate. During follow-up (0.84 years) 3 non-fatal thromboembolic events were recorded (1P, 2A) and 6 patients died (3P, 3A), none of them from a thromboembolic complication. However, 3 deaths were secondary to severe haemorrhagic complications (1P, 2A). Non-fatal haemorrhagic complications occurred more often in group A (n = 10, 13.1 pour cent) compared with group P (n = 1, 1.2 pour cent), p = 0.003.</AbstractText>The FFAACS study was not able to show any therapeutic benefit from the addition of aspirin to anticoagulant in patients with high-risk AF. Such a combination increased the incidence rate of bleeding complications, which therefore greatly reduces its potential overall benefit.</AbstractText> |
4,089 | [Prophylactic value of automatic implantable defibrillators: a case report of a patient with asymptomatic Brugada syndrome]. | The authors report the case of an asymptomatic 32 year old man with no family history of sudden death but with ECG changes suggesting Brugada's syndrome. He underwent implantation of an automatic defibrillator after inducible syncope ventricular fibrillation had been demonstrated during electrophysiological investigation. The later occurrence of three episodes of ventricular fibrillation treated by the defibrillator confirmed a posteriori the logic of this therapeutic approach. |
4,090 | [Operative risk factors and polyvalvular cardiac surgery]. | The aim of this study was to identify risk factors for morbidity and mortality in cardiac valvular surgery. Two hundred and fifty-four patients underwent polyvalvular surgery between May 1996 and December 1998. The mean age was 36.8 years (range 4-66 years) and the group comprised 148 women. Two subgroups were defined: the first (184 patients), characterised by associated mitral and tricuspid valve disease: the second (70 patients), characterised by associated mitral and aortic valve disease with a tricuspid lesion in about half the cases. The risk factors of morbidity and mortality analysed were: Clinical: previous history of cardiac failure, NYHA classification, atrial fibrillation and cardiothoracic index. Doppler echocardiographic: left ventricular end systolic dimension > 50 mm, left ventricular and diastolic dimension > 70 mm, fractional shortening < 28%, ejection fraction < 40%: systolic pulmonary artery pressure > 30 mmHg. Haemodynamic: capillary wedge pressure > 20 mmHg, systolic pulmonary artery pressure > 30 mmHg. The authors identified three statistically significant risk factors for operative morbidity and mortality in polyvalvular cardiac surgery: Previous history of one or more episodes of cardiac failure NYHA functional Classes III or IV fractional shortening < 28%. The morbidity and mortality were lower when patients were operated before these poor prognostic factors were observed. |
4,091 | [Comparative incidence of protrusive atheromatous plaques of the thoracic artery in patients with atrial fluter and atrial fibrillation]. | Although it has been demonstrated recently that in patients with atrial fibrillation, protrusive atheromatous plaques of the thoracic aorta (thickness 4 mm) and left atrial abnormalities such as thrombosis, spontaneous contrast and low atrial blood flow velocities carry an additional embolic risk, this has not yet been studied in atrial flutter. Out of 2493 patients undergoing transoesophageal echocardiography between September 1993 and December 1997, 271 consecutive patients in atrial flutter (N = 41) or fibrillation (N = 230) for over 48 hours, underwent transoesophageal echocardiography before cardioversion. Patients with atrial flutter were compared with those with atrial fibrillation. Their characteristics were comparable with respect to age (68 +/- 13 and 67 +/- 12 years respectively, p = 0.628), sex ratio (men 66 and 54% respectively, p = 0.212), previous thromboembolic disease (5 and 15% respectively, p = 0.126). The incidence of protrusive aortic atheroma (12 and 11% respectively, p = 0.919), of spontaneous contrast in the thoracic aorta (15 and 14% respectively, p = 0.847) were identical in both groups. The left atrium was significantly smaller (3.1 +/- 0.7 and 6 +/- 3 cm2 respectively, p = 0.001), spontaneous atrial contrast less frequent (17 and 37% respectively, p = 0.024) and the velocities of atrial emptying higher (47 +/- 10 and 30 +/- 10 cm/s respectively, p = 0.030) in patients with flutter compared with atrial fibrillation. There was no difference in left ventricular fractional shortening (30 +/- 10 and 33 +/- 13% respectively, p = 0.630), the presence of rheumatic valvular disease (5 and 12%, p = 0.301), left atrial diameter (43 +/- 7 and 45 +/- 8, p = 0.134), right atrial surface area (16 +/- 4 and 17 +/- 6 cm2, p = 0.384) or in intraatrial thrombosis (2 and 3%, p = 0.888) respectively. These results show a high prevalence of protrusive atheroma of the thoracic aorta both in atrial flutter and in atrial fibrillation, and fewer left atrial abnormalities in patients with flutter. |
4,092 | Do current dual chamber cardioverter defibrillators have advantages over conventional single chamber cardioverter defibrillators in reducing inappropriate therapies? A randomized, prospective study. | Supraventricular tachyarrhythmias are the main cause of inappropriate therapies in patients with conventional single chamber implantable cardioverter defibrillators (VVI-ICD). It was anticipated that dual chamber cardioverter defibrillators (DDD-ICD), with their capacity to analyze atrial and ventricular rhythm, could substantially reduce inappropriate therapies.</AbstractText>Our prospective study included 92 patients (87 men; mean age 61 +/- 12.7 years) who were randomly assigned to a VVI-ICD (45 patients) or a DDD-ICD (47 patients). Both groups were followed for 7.5 +/- 3.5 and 7.6 +/- 4.1 months, respectively. During the follow-up period, overall 725 ventricular tachycardia (VT)/ventricular fibrillation (VF) episodes were recorded in 45 (49%) of 92 patients. Of these episodes, 404 (56%) occurred in the VVI-ICD group and 321 (44%) episodes occurred in the DDD-ICD group. Twenty-three (51%) patients in the VVI-ICD group and 22 (47%) patients in the DDD-ICD group (P = 0.8) developed VT/VF. Overall, 73 (10%) of 725 treated episodes were inappropriate in 6 (13%) patients in the VVI group and in 10 (21%) patients in the DDD-ICD group (P = 0.2). There were 22 (31%) inappropriately treated episodes in the VVI-ICD group and 51 (69%) in the DDD-ICD group. Thirty-two of the 51 inappropriate episodes in the DDD-ICD patients resulted from intermittent atrial sensing problems that led to failure of the respective dual chamber algorithms. Nonfatal complications occurred in 6 (13%) patients in the VVI-ICD group and in 3 (6%) patients in the DDD-ICD group (P = 0.7).</AbstractText>We conclude that the implanted DDD-ICD and conventional VVI-ICD are equally safe and effective for therapy of life-threatening ventricular tachyarrhythmias. Although DDD-ICDs allow better rhythm classification, the applied detection algorithms do not offer benefits in avoiding inappropriate therapies during supraventricular tachyarrhythmias.</AbstractText> |
4,093 | Sustained atrial arrhythmias in adults late after repair of tetralogy of fallot. | We determined the prevalence of sustained atrial tachyarrhythmia (AT) in adults late after repair of tetralogy of Fallot (ToF) and examined its impact on subsequent heart failure, reoperation, and mortality. Ventricular arrhythmias are associated with increased morbidity and mortality in patients with repair of ToF. The clinical impact of AT in this population has not been established. A retrospective cohort study of 242 patients with repaired ToF identified 29 patients (prevalence of 12%) with sustained episodes of AT. Patients with repaired ToF but without sustained arrhythmia (n = 213) constituted a comparison group. Baseline characteristics and clinical outcomes in the 2 groups were compared. An echocardiographic analysis compared 15 patients with AT and 15 matched for age at operation and timing of echocardiography. The development of AT was associated with substantial morbidity including congestive heart failure, reoperation, subsequent ventricular tachycardia, stroke, and death (combined events, 20 of 29 patients [69%]). The rate of combined events (congestive heart failure, stroke, and deaths) in the 213 "arrhythmia-free" patients was 30% (64 of 213 patients). Event-free survival after repair was 18 +/- 2 years for the AT group and 28 +/- 1 years for the arrhythmia-free group (p < 0.001). Patients with AT were older at surgical repair (25 +/- 16 vs 10 +/- 9 years, p = 0.001), and at most recent assessment were aged 48 +/- 12 vs 32 +/- 10 years (p = 0.001). The AT group had a higher mean right atrial volume and proportion of significant pulmonary regurgitation than matched controls. The development of AT in the adult late after ToF repair identifies patients at risk and is associated with older age at repair, a higher frequency of hemodynamic abnormalities, and increased morbidity. |
4,094 | Safety, feasibility, and diagnostic accuracy of accelerated high-dose dipyridamole stress echocardiography. | Protocols for dipyridamole stress testing have evolved in the last 16 years in the neverending quest of optimal diagnostic accuracy and user friendliness. Higher dipyridamole dose in a shorter infusion time provides higher sensitivity, but concern over safety is still controversial. An accelerated high-dose (0.84 mg/kg in 6 minutes without atropine) dipyridamole stress test was performed on 1,295 patients in 2 echocardiographic laborotories: Institute of Clinical Physiology of Pisa and Niguarda Hospital of Milan. During testing, there were no deaths and no patients had ventricular fibrillation. Major adverse reactions occurred in 3 cases (1 every 431 studies): 1 myocardial infarction, 1 brief cardiac asystole, and 1 transient ischemic attack. Overall feasibility was 97%. In 66 patients with normal function at rest who were evaluated off therapy, with coronary angiography performed independently of test results, the accelerated high-dose protocol showed a sensitivity of 85% (confidence interval [CI] 73% to 92%) and a specificity of 93% (CI 83% to 97%) for angiographically assessed coronary artery disease (quantitatively assessed diameter reduction > or = 50%). Diagnostic accuracy of the accelerated high dose was 89% (CI 79% to 95%). Thus, accelerated high-dose dipyridamole stress echocardiography was reasonably safe and well tolerated. This protocol is especially appealing for its excellent diagnostic accuracy coupled with the short imaging time and no need for drug cocktails. |
4,095 | Antiarrhythmic effects of adenosine on ischemia-induced ventricular fibrillation. | The antiarrhythmic efficacy of adenosine during states of AV-nodal reentrant tachycardias is well known and clinically established. Adenosine is also able to reduce ventricular arrhythmias when applied before coronary ligation in rats. Hypoxia or ischemia leads to an increased production of adenosine by cardiac myocytes. The purpose of this study was to evaluate if adenosine also has a direct antiarrhythmic effect on ischemia-induced ventricular fibrillation.</AbstractText>In this study, the antiarrhythmic effects of adenosine on ventricular fibrillation during global (low flow) ischemia were evaluated in isolated guinea pig hearts perfused by the method of Langendorff.</AbstractText>Adenosine showed a dose-dependent prolongation of the peak to peak interval of the ventricular ECG signal during ventricular fibrillation until ventricular flutter or tachycardia occurred at a concentration of 2 mmol/L. At a concentration of 20 mmol/L, adenosine converted ventricular fibrillation into ventricular tachycardia with intermittent periods of asystole. This conversion of ventricular fibrillation to asystole was antagonised by 200 micromol/L theophylline.</AbstractText>Adenosine appears to have an antiarrhythmogenic effect both in supraventricular and ventricular rhythm disturbances. During myocardial infarction, where huge amounts of adenosine are present in ischemic regions, asystole may respond to adenosine antagonists.</AbstractText> |
4,096 | Mortality after coronary artery occlusion in different models of cardiac hypertrophy in rats. | Chronic treatment with minoxidil induces cardiac trophic and sympathetic responses, which may increase the propensity for lethal arrhythmias. To test this hypothesis, acute coronary artery occlusion was performed in conscious normotensive rats treated for 2 or 5 weeks with minoxidil with the use of a 2-stage approach to cause a myocardial infarction. For comparison, rats with aortocaval (A-V) shunts and spontaneously hypertensive rats (SHR) were studied. Minoxidil increased left ventricular and right ventricular weights by 15% to 20%, and the A-V shunt increased these weights by 30% to 40%. In SHR, left ventricular weight was increased by 50%, and right ventricular weight was increased by 25%. In rats treated with minoxidil for 5 weeks, coronary artery occlusion caused a rapid and marked mortality, and 4 hours after myocardial infarction, only 18% of these rats were alive versus 61% of the control rats. In rats with the A-V shunt, coronary artery occlusion was also associated with increased mortality, and after 6 hours, 33% were still alive compared with 59% of the control rats. In contrast, SHR with marked hypertension and cardiac hypertrophy showed only a minor increase in mortality (survival rates were 53% versus 60% in SHR versus Wistar-Kyoto rats, respectively). Mortality was preceded by high arrhythmia scores, and ventricular fibrillation was the cause of death. Discontinuation of minoxidil for 1 week, sympathetic blockade with nadolol or clonidine, or blockade of the renin-angiotensin system with enalapril or losartan did not improve minoxidil-induced excess mortality. We conclude that ventricular stretch and other mechanisms (eg, cardiac vagal activity) in rats appear to be more potent than hypertension-induced left ventricular hypertrophy in predisposing for lethal arrhythmias in the setting of acute ischemia. |
4,097 | Transvenous low energy internal cardioversion for atrial fibrillation: a review of clinical applications and future developments. | Low energy internal atrial cardioversion can be performed by delivering biphasic shocks between transvenous catheters positioned within the cardiac chambers or great vessels. Delivery of shocks results in effective cardioversion at energies < 6-10 J and the procedure can be effective even when external cardioversion has failed. Shock induced discomfort varies from patient to patient, but the procedure can be usually performed without general anesthesia and eventually under mild sedation. Nevertheless, tolerability has to be improved by obtaining a substantial reduction in defibrillating thresholds. With regard to safety, delivery of shocks for defibrillating the atria implies a potential risk of inducing ventricular fibrillation; to minimize this risk, shock delivery must be synchronous to the QRS and should be avoided during rapid RR cycles (< 300 ms). Presently, transvenous low energy cardioversion is an investigational procedure, but a widening of indications is expected in the near future. The cost of the procedure, which remains invasive and requires a brief hospital stay, must be balanced with the benefit of restoring sinus rhythm and the possibility of maintaining sinus rhythm for the medium- to long-term. Experimental and clinical investigations of low energy internal cardioversion have resulted in the development of devices for atrial defibrillation whose clinical role and cost-benefit ratio is currently under evaluation. |
4,098 | Prospective randomized comparison of 50%/50% versus 65%/65% tilt biphasic waveform on defibrillation in humans. | It is unknown if there is a single optimal biphasic waveform for defibrillation. Biphasic waveform tilt may be an important determinant of defibrillation efficacy. The purpose of this study was to compare acute defibrillation success with a three-electrode configuration in humans using 50%/50% versus 65%/65% tilt truncated exponential, biphasic waveforms delivered through a 110-microF capacitor. Acute DFTs for biphasic waveforms with 50%/50% versus 65%/65% tilt were measured in random order in 60 patients using a binary search method. The electrode configuration consisted of a RV coil as the cathode, and a SVC coil plus a pectoral active can emulator (CAN) as the anode. The waveforms were derived from an external voltage source with 110-microF capacitance, and the leading edge voltage of phase 2 was equal to the trailing edge voltage of phase 1. Stored energy DFT (9.2 +/- 5.7 [50%/50%] vs 10.8 +/- 6.4 [65%/65%] J, P = 0.007), current DFT (10.9 +/- 4.0 [50%/50%] vs 12.0 +/- 4.4 [65%/65%] A, P = 0.002) and voltage DFT (391 +/- 118 [50%/50%] vs 424 +/- 128 [65%/65%] V, P = 0.004) were significantly lower for the 50%/50% tilt waveform versus the 65%/65% tilt waveform using this three-electrode configuration and a 110-microF capacitor. For an RV(-)/SVC plus CAN(+) electrode configuration and a 110-microF capacitor, a 50%/50% tilt biphasic waveform results in a 15% reduction in energy DFT, 9% reduction in current DFT, and 8% reduction in voltage DFT versus a 65%/65% tilt biphasic waveform. |
4,099 | Paroxysmal tachycardia in children and teenagers with normal sinus rhythm and without heart disease. | The purpose of this study was to evaluate the value of esophageal programmed stimulation in children and teenagers with normal sinus rhythm ECG and normal noninvasive studies, having palpitations and syncope, and no documented tachycardias. Paroxysmal tachycardias are frequent in children and are often related to accessory connection. These tachycardias are sometimes difficult to prove. Transesophageal atrial pacing was performed at rest and during infusion of isoproterenol in 31 children or adolescents aged 9-19 years (16 +/- 3 years) with normal sinus rhythm ECG and suspected or documented episodes of paroxysmal tachycardia. Sustained tachycardia was induced in 27 patients, at rest in 13 patients, and after isoproterenol in 14 remaining patients. Atrioventricular nodal reentrant tachycardia was found as the main cause of paroxysmal tachycardia (22 cases). Six patients were followed by a vagal reaction and dizziness. These patients had spontaneous tachycardia with syncope. In three other patients, atrial fibrillation was also induced. Concealed accessory pathway reentrant tachycardia was identified in three patients. In two patients, a regular wide tachycardia with right bundle branch block morphology was induced; the diagnosis of verapamil-sensitive ventricular tachycardia was made in a second study by intracardiac study. In conclusion, atrioventricular nodal reentrant tachycardia was found as the main cause of symptoms in children with normal sinus rhythm ECG. Syncope is frequently associated and provoked by a vagal reaction. This diagnosis could be underestimated in adolescents frequently considered as hysterical because noninvasive studies are negative. |
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