Antiarrhythmic drugs versus implantable defibrillators: the need for a randomized controlled study

Recognition and Management of Cardiac Arrhythmias: Part II. Ventricular Arrhythmias and Bradyarrhythmias

This review discusses the treatment of ventricular arrhythmias and bradyarrhythmias. Recent studies addressing the management of nonsustained ventricular arrhythmias in patients with congestive heart failure and those recovering from myocardial infarction are discussed. Determination of the origin of wide QRS complex tachycardia is usually possible at the bedside and the diagnostic criteria are provided. Therapy to prevent recurrent ventricular tachycardia or ventricular fibrillation is difficult and controversial. A widely accepted approach based on electrophysiologic testing and implantable defibrillators appears to be the most effective. Recognition and management of common bradyarrhythmias including the indications for pacemakers are discussed.

Implantable devices versus antiarrhythmic drug therapy in recurrent ventricular tachycardia and ventricular fibrillation

The implantable cardioverter defibrillator (ICD) protects patients from sudden cardiac death due to ventricular tachyarrhythmias. The capability of an improved overall survival of high-risk patients in comparison to the best pharmacologic therapy has been evaluated over the last few years in prospective randomized trials. In patients with a history of resuscitated ventricular fibrillation (VF) or unstable ventricular tachycardia (VT), the ICD was superior to therapy with amiodarone in 3 large trials involving 2,024 patients. At 2-year follow-up, ICD therapy was associated with a relative reduction in the risk of death of 20% to 30%. With respect to primary prevention of arrhythmogenic death, data are less convincing. The Multicenter Automatic Implantable Defibrillator (MADIT) study proved superiority of ICD therapy over medical treatment in coronary patients with depressed left ventricular function, nonsustained VT, and inducible but not suppressible sustained VT/VF. The second trial, the Coronary Artery Bypass Graft (CABG)-Patch trial, failed to show a similar superiority in 900 patients with an ejection fraction of < or = 35% and an abnormal signal-averaged electrocardiograph undergoing coronary artery bypass grafting. Thus, the role of device therapy for primary prevention of sudden death has not been established. Future prospective studies are needed to clarify this issue.

Causes of death in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial

OBJECTIVES

This study analyzed the causes of death in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial.

BACKGROUND

Both implantable cardioverter-defibrillators (ICDs) and antiarrhythmic drugs (AADs) are used as mainstays of treatment for life-threatening ventricular arrhythmias in patients who have survived either ventricular fibrillation or sustained ventricular tachycardia with hemodynamic compromise and serious symptoms. The AVID Trial compared the effectiveness of these two therapies. Survival was better with the ICD. Assessment of the cause of death should help to determine the mechanism of improvement in survival with the ICD.

METHODS

Of 1,016 patients enrolled in the AVID Trial, 202 patients died. The mode of death was determined by the unblinded Principal Investigator and independently by an Events Committee, which reviewed materials meticulously blinded with respect to treatment. Deaths were classified as cardiac or noncardiac. Cardiac deaths were further classified as arrhythmic or nonarrhythmic, and causes of noncardiac death were identified.

RESULTS

Deaths were more frequent in patients treated with an AAD (n = 122), compared with patients treated with the ICD (n = 80), unadjusted p < 0.001, p = 0.012 adjusted for sequential monitoring. In AVID, 157 deaths were cardiac, and 79 were arrhythmic. The major effect of the ICD was to prevent arrhythmic death (AAD = 55, ICD = 24, nominal unadjusted p < 0.001). Nonarrhythmic cardiac deaths were equal (AAD = 39, ICD = 39). Patients treated with an AAD had a slightly greater incidence of noncardiac deaths (28 vs. 17, p = 0.053), primarily due to pulmonary and renal causes.

CONCLUSIONS

The ICD is more effective than an AAD in reducing arrhythmic cardiac death, while nonarrhythmic cardiac death is unchanged. Of note, apparent arrhythmic death still seems to constitute 38% of all cardiac deaths despite treatment with an ICD. However, the ICD remains superior to an AAD in prolonging survival after life-threatening arrhythmias.

Could implantable cardioverter defibrillators provide a human model supporting the learned helplessness theory of depression?

Affective symptoms were examined retrospectively in 25 patients following placement of implantable cardioverter defibrillators (ICD) which can produce intermittent shocks without warning in response to cardiac ventricular arrhythmias. The number of ICD random, uncontrollable discharge shocks and pre-ICD history of psychological distress (i.e., depression and/or anxiety) were documented in all patients using a demographics questionnaire and a standardized behavioral/psychological symptoms questionnaire (i.e., Symptom Checklist-90 Revised). ICD patients were dichotomized into two groups: those without a history of psychological distress prior to ICD (n = 18) and those with a history of psychological distress prior to ICD (n = 7). In ICD patients without a prior history, results indicated that quantity of ICD discharge shocks was significantly predictive of current reported depression (r = 0.45, p = 0.03) and current reported anxiety (r = 0.51, p = 0.02). Conversely, in patients with a reported history of psychological distress, there was no significant relationship found between quantity of discharge shocks and current reported depression or anxiety. This study may provide evidence in support of a human model of learned helplessness in that it supports the notion that exposure to an unavoidable and inescapable aversive stimulus was found to be related to patients' reported depression. Further studies may wish to prospectively consider a larger sample as well as a more comprehensive assessment of premorbid psychological symptoms.

Health-related quality-of-life assessment of patients with life-threatening ventricular arrhythmias

The purpose of this study was to determine whether treatments for life-threatening ventricular arrhythmias are associated with quality-of-life (QOL) and psychological distress. Multidimensional measures of QOL and psychological distress were used to cross-sectionally compare patients with ICDs to patients treated with antiarrhythmic drugs and patients without serious cardiac conditions. The sample consisted of 157 patients: 35 patients treated with antiarrhythmic medication only, 24 patients treated with ICD only, 25 patients treated with ICD and antiarrhythmic medication, and 73 controls. Patients completed the Medical Outcomes Study SF-36 health survey, the Brief Symptom Inventory, and background questionnaires. There were no significant differences in self-reported QOL and psychological distress between patients with or without ICD, and the occurrence of defibrillator shocks was unrelated to QOL and psychological distress. However, patients treated with antiarrhythmic drugs reported greater QOL impairment in physical functioning, vitality, emotional role limitations, and sleep, as well as greater psychological distress than patients not treated with antiarrhythmics. These limitations may be attributed to adverse effects arising from antiarrhythmic pharmacotherapy. Results of the present investigation suggest that QOL and psychological distress are maintained among ICD patients, whereas treatment with antiarrhythmic drugs are associated with a diminished QOL and greater psychological distress. These findings may assist cardiologists to select the optimal treatment for life-threatening ventricular arrhythmias that minimizes disturbances in health-related QOL and psychological distress and increases patient compliance.

Feasibility of a noncontact catheter for endocardial mapping of human ventricular tachycardia

BACKGROUND

Catheter ablation of ventricular tachycardia (VT) is limited by difficulty in identifying suitable sites for ablation. This study assesses use of a system capable of simultaneous endocardial mapping of the human left ventricle to map and guide radiofrequency (RF) catheter ablation of VT.

METHODS AND RESULTS

A catheter-mounted noncontact multielectrode array was used to reconstruct 3360 electrograms, superimposed onto a computer-simulated endocardial model. Of 24 patients studied, 20 had ischemic heart disease. Exit sites were demonstrated by the noncontact system in 80 (99%) of 81 VTs, with complete VT circuits traced in 17 (21%). In another 37 VTs, 36+/-30% (mean+/-SD) of the diastolic interval was identified. Thirty-eight VT morphologies were ablated with 154 RF energy applications. Successful ablation was achieved by 77% of RF applications to relevant diastolic activity identified by the system and was significantly more likely (P<0.0001) than by RF at the VT exit or remote from diastolic activation. Over a mean follow-up of 1.5 years, 14 patients (64%) have had no recurrence of VT, and only 2 target VTs (5.3%) have recurred. Five patients have had recurrence of other VTs.

CONCLUSIONS

This noncontact mapping system identified diastolic portions of the circuit in most VTs studied and can safely map and guide ablation of human VT.

The top ten fallacies of nonsustained ventricular tachycardia

Nonsustained ventricular tachycardia (NSVT) continues to remain a subject of controversy. This is true despite a wealth of epidemiologic and basic/clinical laboratory findings that have accumulated during the past 2 decades. However, these data not only generate the impetus to conduct further research, but also provide compelling arguments against continued adherence to time honored precepts about NSVT that evolved since the inception of the "PVC Hypothesis," although never substantiated by rigorous scientific inquiry. This paper discusses the "top ten" fallacies of NSVT and details the data that support abandonment of them.

The side effect profile of class III antiarrhythmic drugs: focus on d,l-sotalol

Class III antiarrhythmic drugs have been under extensive clinical investigation as safer, more effective alternatives to class I drugs, which have recognized risks in selected populations. Class III drugs prolong the action potential duration of myocardial cells, resulting in a lengthening of the effective refractory period. This pharmacologic activity has antiarrhythmic properties, but it may induce a distinctive form of proarrhythmia known as torsades de pointes. Amiodarone and d,l-sotolol are class III drugs that have been available for many years. In addition to their ability to prolong refractoriness, these drugs have other pharmacodynamic properties. Recent antiarrhythmic drug discovery has focused on the identification and development of selective or so-called pure class III drugs that are devoid of additional actions. Investigators have hoped that these drugs would be as effective as sotalol and amiodarone but have fewer adverse effects. Accumulating data, however, indicate that complex compounds exhibiting antiadrenergic and other electrophysiologic properties may be superior to pure class III agents.

Predictors of psychosocial adjustment in patients with implantable cardioverter defibrillators

Predictors of psychological distress/adjustment were examined in 25 patients following placement of ICDs. Patients completed a demographic questionnaire and a standardized questionnaire of psychological symptoms (i.e., Symptom Checklist-90 Revised; SCL-90-R). The number of discharges categorized by the patient as inappropriate and appropriate were also ascertained. The number of ICD discharges categorized as inappropriate and diminished levels of physical activity (r = 0.53 and 0.63, P < 0.01, respectively) did significantly relate to overall psychological distress. In addition, after controlling for age and prior psychiatric and physical health status through a stepwise multiple regression analysis, the occurrence of ICD discharges categorized as inappropriate and diminished physical activity continued to significantly predict overall psychological distress (R2 = 0.41, P < 0.01). However, the number of ICD discharges categorized as appropriate did not significantly predict overall psychological distress. The results of this investigation suggest that further refinement of the ICD could reduce the risk of exposure to potential psychological distress, and an analysis of prior and anticipated patient physical activity levels should be a factor when calibrating minimum ICD discharge threshold levels.

Current concepts in electrical defibrillation

The electrical defibrillator has been proven to be a life-saving device in the treatment of cardiac arrest due to ventricular tachycardia or ventricular fibrillation. An understanding of the physiology and technology behind this device is useful for providers of emergency care. In this article, we review the current concepts in electrical defibrillation and briefly discuss the developmental history. The physiology and the technical considerations will make up the bulk of the discussion. The latest developments in electrical defibrillation also will be reviewed.

Improved survival with an implanted defibrillator in patients with coronary disease at high risk for ventricular arrhythmia. Multicenter Automatic Defibrillator Implantation Trial Investigators

BACKGROUND

Unsustained ventricular tachycardia in patients with previous myocardial infarction and left ventricular dysfunction is associated with a two-year mortality rate of about 30 percent. We studied whether prophylactic therapy with an implanted cardioverter-defibrillator, as compared with conventional medical therapy, would improve survival in this high-risk group of patients.

METHODS

Over the course of five years, 196 patients in New York Heart Association functional class I, II, or III with prior myocardial infarction; a left ventricular ejection fraction < or = 0.35; a documented episode of asymptomatic unsustained ventricular tachycardia; and inducible, nonsuppressible ventricular tachyarrhythmia on electrophysiologic study were randomly assigned to receive an implanted defibrillator (n = 95) or conventional medical therapy (n=101). We used a two-sided sequential design with death from any cause as the end point.

RESULTS

The base-line characteristics of the two treatment groups were similar. During an average follow-up of 27 months, there were 15 deaths in the defibrillator group (11 from cardiac causes) and 39 deaths in the conventional-therapy group (27 from cardiac causes) (hazard ratio for overall mortality, 0.46; 95 percent confidence interval, 0.26 to 0.82; P=0.009). There was no evidence that amiodarone, beta-blockers, or any other antiarrhythmic therapy had a significant influence on the observed hazard ratio.

CONCLUSIONS

In patients with a prior myocardial infarction who are at high risk for ventricular tachyarrhythmia, prophylactic therapy with an implanted defibrillator leads to improved survival as compared with conventional medical therapy.

Drugs or implantable cardioverter-defibrillators in patients with poor left ventricular function?

Poor left ventricular function is a predictor of sudden death. Both antiarrhythmic drugs and implantable cardioverter-defibrillators (ICDs) promise to reduce the sudden death rate in these patients and consequently improve survival. In patients without spontaneous ventricular tachyarrhythmias, only beta-blocking agents and amiodarone have been shown to reduce sudden death and improve survival in some studies, whereas class I antiarrhythmic drugs increased mortality. For patients with documented ventricular tachyarrhythmias, protection against sudden death by serially tested class I antiarrhythmic drugs is at best moderate. There is some evidence suggesting that therapy with class III antiarrhythmic drugs, either amiodarone or dl-sotalol, may reduce sudden death rates and improve overall mortality in comparison to therapy with class I antiarrhythmic drugs. ICDs have been shown to prevent sudden death reliably. In published patient cohorts in which only patients who were not inducible off antiarrhythmic drugs or still inducible on antiarrhythmic drugs received an ICD, the ICD seemed to improve overall survival in comparison to class I antiarrhythmic drugs. A small prospective randomized study that compared a conventional therapy strategy to primary ICD implantations showed an improved outcome with ICDs as therapy of first choice. However, these studies included many patients treated with class I antiarrhythmic drugs considered to be less effective. In matched control studies comparing the ICD to amiodarone or dl-sotalol, less sudden deaths and an improved overall survival could be shown for the ICD in general without stratification for left ventricular function. Thus, in patients with hemodynamically nontolerated ventricular tachyarrhythmias, the ICD seems to improve survival in comparison to class I antiarrhythmic drugs, dl-sotalol, or amiodarone. However, in patients with poor left ventricular function, therapy with ICDs seems to be less cost-effective than in patients with preserved left ventricular function. In patients with very poor left ventricular function who are evaluated for cardiac transplantation, the ICD seems to change only the mode of death from sudden to a nonsudden cardiac death if transplantation cannot be performed soon.

Impact of the implantable defibrillator on mortality: the axiom of overall implantable cardioverter-defibrillator survival

As soon as it was established that the implantable cardioverter-defibrillator (ICD) effectively prevents sudden death, it became axiomatic that whether the ICD will prolong overall survival depends entirely on the population of patients to which it is applied. This axiom of overall ICD survival immediately reveals the only vital question that remains regarding usage of the ICD; namely, How does one select those patients in whom prevention of sudden death by the ICD will also prolong life? This axiom also reveals the essential futility of randomized trials now being conducted for the purpose of discerning the true efficacy of the ICD. Claims to the scientific high ground notwithstanding, if a study asks the wrong question from the beginning, then the design of that study (including whether the study is randomized or nonrandomized), is completely irrelevant. Ideally, funds now being spent on these randomized trials should be diverted to the design and initiation of more appropriate trials, trials that will teach us to select patients for the ICD more effectively. At the very least, however, we should recognize the problems inherent in the ongoing trials, so that when their results are finally published (and are loudly touted by whichever faction feels vindicated by them), we will not be carried away into inappropriate clinical behavior.

Implications of the Electrophysiologic Study versus Electrocardiographic Monitoring trial for controlling ventricular tachycardia and fibrillation

The Electrophysiologic Study versus Electrocardiographic Monitoring (ESVEM) trial had 2 objectives. The first was to determine the accuracy of noninvasive versus invasive means of predicting the efficacy of drug treatment for ventricular tachycardia/ventricular fibrillation (VT/VF). A second objective was to determine the relative efficacies of 7 antiarrhythmic drugs used in the treatment of ventricular tachyarrhythmias. ESVEM was the first opportunity to compare prospectively the efficacy, safety, and tolerability of a variety of antiarrhythmic drugs in the same patient population. No significant difference was observed between suppression of spontaneous ventricular arrhythmias on Holter monitoring and suppression of inducible ventricular arrhythmias by electrophysiologic study (EPS) in terms of the ability to predict the success of drug therapy. There was also no difference in predictive accuracy if patients in the electrophysiologic limb showed suppression by Holter monitoring in addition to suppression by EPS. Sotalol was more effective than the other 6 antiarrhythmic drugs, all class I agents, in preventing death and recurrence of arrhythmia. Efficacy compared with placebo, however, was not evaluated. In the EPS limb, sotalol was also statistically more likely to achieve an efficacy prediction than any of the sodium channel blocking drugs. Amiodarone was not used in ESVEM. It has been suggested that these conclusions, which differ from those of other, less controlled, invasive and noninvasive studies, might be because of the particular efficacy criteria used in the ESVEM protocol. Retrospective analyses of the ESVEM data were performed using more rigid efficacy criteria than were used in the original ESVEM analysis: a greater degree of ectopy suppression was required for Holter monitoring, and more stringent efficacy definitions were required in the stimulation protocol of the EPS limb. Results from the retrospective analyses and other studies support the initial ESVEM conclusions. In patients with both spontaneous and inducible sustained ventricular tachyarrhythmias as well as frequent spontaneous premature ventricular contractions, therapy with sotalol (guided by either Holter monitoring or EPS) is a reasonable initial strategy because of its superior initial long-term efficacy and better acute and long-term tolerability compared with sodium channel blocking drugs.

Cardiac electrophysiology: a cost-effective approach

Clinical cardiac electrophysiology is a relatively new discipline, heavily dependent upon new technology that is often expensive. In cardiac pacing, no effective alternative to permanent pacing usually exists for patients with Class I indications, so cost-reduction strategies involve appropriate selection and utilization of hardware and facilities. Cost-effective utilization of radiofrequency ablation and implantable cardioverter-defibrillators requires that these techniques be compared with alternative therapies, usually antiarrhythmic drugs. Both ablation and defibrillator implantation can be shown to be cost effective in selected populations, but a cost-conscious approach to procedures and patient selection can make them cost effective in a broad range of patients.

Major clinical trials assessing the prophylactic use of amiodarone in patients with ventricular tachyarrhythmias

The purpose of this article is to summarize and critique recently completed and ongoing clinical trials assessing the prophylactic use of amiodarone in patients with potentially life-threatening ventricular arrhythmias. Three of the trials compare amiodarone with an implantable cardioverter defibrillator.

Nonpharmacological therapy for malignant ventricular arrhythmias: implantable defibrillator trials

Implantable cardioverter-defibrillators (ICDs) are an important nonpharmacological option in the treatment of malignant ventricular arrhythmias. Technological advances in current devices permit nonthoracotomy implantation with transvenous lead systems using biphasic shocks. Decreasing device size has resulted in pectoral implantation. Battery longevity is still short in comparison with that of pacemakers. Lead failure rates as well as pacing thresholds are significantly higher than those for cardiac pacing lead systems. Other complications of ICD systems include infection, perforation, and thrombosis. The long-term performance of nonthoracotomy lead systems for ICD devices has now been extensively studied. Sudden death recurrence rates for these systems are less than 2% in 3 years and less than 5% at 5 years. Clinical trials with both monophasic and biphasic systems show a high degree of prevention of sudden death. Comparison of ICD outcome with that of drug therapy in three large retrospective studies and two small prospective randomized trials favors improved survival and sudden death prevention with device therapy. However, these studies need corroboration from large prospective trials. Two large prospective trials, CIDS and the AVID study, are now in progress to address this issue.

NASPE/ACC/AHA/ESC medical/scientific statement special report--clinical investigation of antiarrhythmic devices: a statement for healthcare professionals from a Joint Task Force of the North American Society of Pacing and Electrophysiology, the American College of Cardiology, the American Heart Association, and the Working Groups on Arrhythmias and Cardiac Pacing of the European Society of Cardiology

The goal of radiofrequency catheter ablation and the criterion for efficacy is the elimination of arrhythmogenic myocardium. The application of radiofrequency current in the heart clearly results in lower morbidity and mortality rates than thoracic and cardiac surgical procedures in general, and comparisons of therapy with radiofrequency catheter ablation and therapy with thoracic and cardiac surgical procedures in randomized clinical trials are unwarranted. Trials of radiofrequency catheter ablation versus medical or implantable cardioverter defibrillator therapy may be indicated in certain conditions, such as ventricular tachycardia associated with coronary artery disease. Randomized trials are recommended for new and radical departures in technology that aim to accomplish the same goals as radiofrequency catheter ablation. Surveillance using registries and/or databases is necessary in the assessment of long-term safety and efficacy.

Clinical investigation of antiarrhythmic devices. A statement for healthcare professionals from a joint task force of the North American Society of Pacing and Electrophysiology, the American College of Cardiology, the American Heart Association, and the Working Groups on Arrhythmias and Cardiac Pacing of the European Society of Cardiology

The goal of radiofrequency catheter ablation and the criterion for efficacy is the elimination of arrhythmogenic myocardium. The application of radiofrequency current in the heart clearly results in lower morbidity and mortality rates than thoracic and cardiac surgical procedures in general, and comparisons of therapy with radiofrequency catheter ablation and therapy with thoracic and cardiac surgical procedures in randomized clinical trials is unwarranted. Trials of radiofrequency catheter ablation versus medical or implantable cardioverter-defibrillator therapy may be indicated in certain conditions, such as ventricular tachycardia associated with coronary artery disease. Randomized trials are recommended for new and radical departures in technology that aim to accomplish the same goals as radiofrequency catheter ablation. Surveillance using registries and/or databases is necessary in the assessment of long-term safety and efficacy.

Third- and fourth-generation implantable cardioverter defibrillators: current status and future development

Implantable cardioverter defibrillator (ICD) therapy has become the mainstay of therapy for patients with a history of sudden cardiac death or life-threatening ventricular arrhythmias. The current generation of ICDs used for secondary prevention combines features for tachycardia reversion with demand ventricular pacing, antitachycardia pacing, programmable shock therapy, and tachycardia events memory. Although demand pacing and defibrillation is indicated for primary prevention usage of ICDs, the application of antitachycardia pacing modes is more controversial. High energy cardioversion and defibrillation shocks remaining the mainstay of sudden death prevention will be redefined as more effective defibrillation shock modes and lead systems are developed. Fourth-generation ICD systems accomplished a significant reduction of device size and almost universal success using an endocardial lead configuration and pectoral implant. A variety of new directions of ICD therapy in clinical practice such as primary prevention applications and the adjunctive role of antiarrhythmic drug therapy are currently being examined in clinical trials. The concepts underlying initiation of tachyarrhythmias are being studied to develop new approaches to tachycardia prevention. These include rate support, subthreshold stimulation, and multiple site pacing. The current developments of ICD therapy promise continued growth of this technology.