Survival after implantation of the cardioverter defibrillator

Research Update: Materials design of implantable nanogenerators for biomechanical energy harvesting

Implantable nanogenerators are rapidly advanced recently as a promising concept for harvesting biomechanical energy in vivo. This review article presents an overview of the most current progress of implantable piezoelectric nanogenerator (PENG) and triboelectric nanogenerator (TENG) with a focus on materials selection, engineering, and assembly. The evolution of the PENG materials is discussed from ZnO nanostructures, to high-performance ferroelectric perovskites, to flexible piezoelectric polymer mesostructures. Discussion of TENGs is focused on the materials and surface features of friction layers, encapsulation materials, and device integrations. Challenges faced by this promising technology and possible future research directions are also discussed.

Sudden Cardiac Death Unresponsive to Implantable Defibrillator Therapy: An Urgent Target for Clinicians, Industry and Government

A major expansion in utilization of implantable cardioverter-defibrillators (ICDs) is anticipated based on the results of randomized clinical trials (RCT) that demonstrate increased survival in a sizable population of patients with reduced left ventricular function. However, if RCT accurately reflect clinical practice, then a substantial proportion of patients will die suddenly despite ICD implantation. ICD-unresponsive sudden cardiac death (SCD) has been recognized since the initial ICD experience. Yet, despite 25 years of technical advances, the frequency of ICD-unresponsive SCD has not declined. Pooled analysis of RCT indicates a crude rate of ICD-unresponsive SCD of 5%. This may not cause alarm in an average practice, but it comprises about 30% of cardiac deaths. Meta-analyses of RCT show that ICD therapy is associated with a relative risk reduction of SCD of approximately 60%, far less than the greater than 90% efficacy that many expect. The suboptimal performance of ICD therapy accounts for the failure of some RCT to achieve statistically significant effects on survival. The number of patients with ICD-unresponsive SCD is highly correlated with the number of cardiac deaths among control patients as well as ICD recipients. Otherwise, no definite patterns have emerged that clearly distinguish this mode of demise from other modes of cardiac death. Retrospective post-hoc analyses have not revealed distinguishing characteristics of patients with ICD-unresponsive SCD with respect to clinical variables, pre-terminal symptoms or to the setting of the terminal event. Despite advanced storage capabilities of implanted devices, almost no information has become available from RCT regarding the terminal rhythm or the response of the ICD. These observations have implications for clinical management and research. Candidates for ICD implantation based on RCT should be accurately informed about the residual risk of SCD. Investigators seeking to identify populations likely to benefit from ICD therapy based on SCD incidence should recognize that a significant fraction may not respond to ICD therapy. Reducing the incidence of ICD-unresponsive SCD would substantially improve survival and cost-effectiveness related to ICD therapy. Close cooperation between clinicians, investigators and representatives of industry and government is urgently needed to develop strategies to identify patients prone to ICD-unresponsive SCD, to determine its mechanisms and to develop methods of prevention and treatment.

Long-Term Comparison of the Implantable Cardioverter Defibrillator Versus Amiodarone

Background— The implantable cardioverter defibrillator (ICD) is superior to amiodarone for secondary prophylaxis of sudden cardiac death. However, the magnitude of this benefit over long-term follow-up is not known. Thus, our objective was to evaluate the long-term consequences of using amiodarone versus an ICD as first-line monotherapy in patients with a prior history of sustained ventricular tachycardia/ventricular fibrillation or cardiac arrest.

Methods and Results— A total of 120 patients were enrolled at St Michael’s Hospital in the Canadian Implantable Defibrillator Study (CIDS) and were randomly assigned to receive either amiodarone (n=60) or an ICD (n=60). The treatment strategy was not altered after the end of CIDS unless the initial assigned therapy was not effective or was associated with serious side effects. After a mean follow-up of 5.6±2.6 years, there were 28 deaths (47%) in the amiodarone group, compared with 16 deaths (27%) in the ICD group ( P =0.0213). Total mortality was 5.5% per year in the amiodarone group versus 2.8% per year in the ICD group (hazard ratio of amiodarone: ICD, 2.011; 95% confidence interval, 1.087 to 3.721; P =0.0261). In the amiodarone group, 49 patients (82% of all patients) had side effects related to amiodarone, of which 30 patients (50% of all patients) required discontinuation or dose reduction; 19 patients crossed over to ICD because of amiodarone failure (n=7) or side effects (n=12).

Conclusions— In a subset of CIDS, the benefit of the ICD over amiodarone increases with time; most amiodarone-treated patients eventually develop side effects, have arrhythmia recurrences, or die.

Implantable Cardioverter Defibrillator Events in Patients with Asymptomatic Nonsustained Ventricular Tachycardia:

Primary prevention trials have demonstrated that patients with coronary disease, reduced left ventricular function, and nonsustained ventricular tachycardia (NSVT) have improved survival with implantable cardioverter defibrillator (ICD) therapy, presumably secondary to effective termination of life-threatening arrhythmias. However, stored intracardiac electrograms were not always available and specific arrhythmias leading to ICD therapy were not always known. We examined the occurrence of ICD events in 51 consecutive patients who match the described patient profile to determine the frequency of appropriate and inappropriate ICD therapy. ICD detections were noted in 18 (35%) patients during a median follow-up period of 13.1 months. Appropriate therapy for sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) occurred in 11 (22%) patients, with appropriate shocks in 8 (16%) patients and appropriate antitachycardia pacing (ATP) in 4 (8%) patients. The time to first appropriate therapy occurred at a mean of 17 +/- 12 months (median 18 months, range 3-36 months). Inappropriate therapy occurred in 5 (10%) patients with inappropriate shocks in 4 patients and inappropriate ATP in 2 patients. Inappropriate therapy was delivered for supraventricular arrhythmias (SVAs) in 4 patients and for T wave oversensing in 1 patient. The reason for shock therapy was unknown in 1 patient (2%) due to ICD malfunction. The mean arrhythmia rate leading to appropriate therapy for VT/VF was 232 +/- 72 beats/min (range 181-400 beats/min), and the mean rate leading to inappropriate therapy for SVT was 168 +/- 10 beats/min (range 160-180 beats/min). Patients with coronary disease and asymptomatic NSVT commonly receive appropriate defibrillator therapy. These results support the need for ICD implantation for primary prevention, with attention to careful programming of the detection rate to prevent inappropriate therapy.

Factors Determining ICD Implantation in Drug Therapy Patients After Termination of Antiarrythmics Versus Implantable Defibrillators Trial

Because of a significant survival benefit in the defibrillator arm of the Antiarrhythmics versus Implantable Defibrillator (AVID) Trial, patients in the antiarrhythmic drug (AAD) arm were advised to undergo ICD implantation. Despite this recommendation, ICD implantation in AAD patients was variable, with a large number of patients not undergoing ICD implantation. Patients were grouped by those who had been on AAD < 1 year (n = 111) and those on AAD > 1 year (n = 223). Multiple clinical and socioeconomic factors were evaluated to identify those who might be associated with a decision to implant an ICD. The primary reason for patients not undergoing ICD implantation was collected, as well as reasons for a delayed implantation, occurring later than 3 months from study termination. Of 111 patients on AAD for less than 1 year, 53 received an ICD within 3 months compared to 40/223 patients on AAD for more than 1 year (P < 0.001). Patient refusal was the most common reason to not implant an ICD in patients on drug < 1 year; physician recommendation against implantation was the most common in patients on drug > 1 year. Multivariate analysis showed ICD recipients on AAD < 1 year were more likely to be working and have a history of myocardial infarction (MI), while those on AAD > 1 year were more likely to be working, have a history of MI and ventricular fibrillation, and less likely to have experienced syncope, as compared to those who did not get an ICD. Having private insurance may have played a role in younger patients receiving an ICD.

Limited predictive value of inducible sustained ventricular tachycardia for future occurrence of spontaneous ventricular tachycardia in patients with coronary artery disease and relatively preserved cardiac function

To evaluate the significance of inducible sustained ventricular tachycardia (VT) in patients with coronary artery disease and relatively preserved cardiac function, 33 patients who met the following criteria were studied; documented nonsustained VT but no history of life-threatening arrhythmia, inducible sustained VT at electrophysiologic study, and implantation of a cardioverter-defibrillator. Eighteen patients developed clinical sustained VT within 2 years. By univariate analysis, left ventricular ejection fraction (EF) and the cycle length of induced VT were associated with clinical VT occurrence. By multivariate analysis, however, EF was the only independent predictor. Among 23 patients with EF <or=40%, 16 patients developed clinical sustained VT compared to 2 of 10 patients with EF >40% (P <.01). In coronary artery disease patients with relatively preserved EF, the incidence of clinical VT is considerably low even though sustained VT is inducible. Inducible VT is therefore not appropriate for risk stratification in this patient population.

Effectiveness of implantable defibrillators for preventing arrhythmic events and death: a meta-analysis

OBJECTIVES

The aim of this study was to compare the effectiveness of the implantable cardioverter defibrillator (ICD) and medical strategies for prevention of arrhythmic events and death.

BACKGROUND

The ICD is a potential strategy to reduce mortality in patients at risk of sudden death.

METHODS

The MEDLINE, EMBASE, and Cochrane Library electronic databases were searched from January 1966 to April 2002. All published randomized controlled trials comparing ICD implantation with medical therapy were reviewed. Four independent reviewers extracted data on all-cause mortality, nonarrhythmic death, and arrhythmic death using a standardized protocol.

RESULTS

Nine studies including over 5,000 patients were synthesized using both fixed-effects and random-effects models. The primary and secondary prevention trials showed a significant benefit of the ICD with respect to arrhythmic death, with relative risks (RR) of 0.34 and 0.50, respectively (both p < 0.001). The mortality benefit of the ICD was entirely attributable to a reduction in arrhythmic death (all trials: p < 0.00001). Whereas the secondary prevention trials exhibited a robust decrease in all-cause ICD mortality (RR 0.75; p < 0.001), the pooled primary prevention trials demonstrated decreased all-cause ICD mortality (RR 0.66; p < 0.05) which was dependent on selected individual trials. The disparity in ICD-related mortality reductions in the primary prevention trials was related to variability in the incidence of arrhythmic death between individual studies.

CONCLUSIONS

Although the ICD decreases the risk of arrhythmic death, its impact on all-cause mortality is related to the underlying risk of arrhythmia-related death relative to competing causes. Given the cost of the device strategy, policies of targeted intervention based on the future risk of arrhythmia are warranted.

Electrophysiologically guided amiodarone therapy versus the implantable cardioverter-defibrillator for sustained ventricular tachyarrhythmias after myocardial infarction: results of long-term follow-up

OBJECTIVES

We sought to compare the long-term survival rates of patients with sustained ventricular tachyarrhythmia after myocardial infarction (MI) who were treated according to the results of electrophysiological (EP) study either with amiodarone or an implantable cardioverter-defibrillator (ICD).

BACKGROUND

Patients with sustained ventricular tachyarrhythmias after MI are at high risk of sudden cardiac death (SCD). However, data comparing the long-term survival rates of patients treated with amiodarone or ICD, according to the results of EP testing, are lacking.

METHODS

Patients underwent a first EP study at baseline and a second one after a loading dose of amiodarone of 14 +/- 2.9 g. According to the results of the second EP study, patients were classified either as responders or non-responders to amiodarone; non-responders were eventually treated with an ICD.

RESULTS

Eighty-four consecutive patients with MI (78 men; 21-77 years old; mean left ventricular (LV) ejection fraction 36 +/- 11%) were consecutively included. Forty-three patients (51%) were responders, and 41 patients (49%) were non-responders to amiodarone therapy. During a mean follow-up period of 63 +/- 30 months, SCD and total mortality rates were significantly higher in the amiodarone-treated patients (p = 0.03 and 0.02, respectively).

CONCLUSIONS

The long-term survival of patients with sustained ventricular tachyarrhythmias after MI, with depressed LV function, is significantly better with an ICD than with amiodarone therapy, even when stratified according to the results of the EP study. These patients should benefit from early ICD placement, and any previous amiodarone treatment seems to have no additional value.

Sudden death in patients with implantable cardioverter defibrillators: the importance of post-shock electromechanical dissociation

OBJECTIVES

The purpose of this study was to determine the mechanisms of sudden death (SD) in patients with ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]) treated with an implantable cardioverter defibrillator (ICD).

BACKGROUND

Despite ICD therapy, some patients with VT/VF still die suddenly. Optimal ICD use requires determination of the mechanisms of these residual SDs.

METHODS

We reviewed 320 patient deaths during trials of Medtronic transvenous ICD systems (Medtronic Inc., Minneapolis, Minnesota). Sudden deaths were further categorized according to mechanism. Post-shock electromechanical dissociation (EMD) describes a scenario where VT/VF was appropriately detected and treated by an ICD shock that restored a physiologic rhythm, but death still occurred immediately by EMD.

RESULTS

A mode of death could be ascribed for 317 patients-90 (28%) were sudden, 156 (49%) were non-sudden cardiac, and 71 (22%) were noncardiac. A mechanism of SD was proposed for 68 patients-20 (29%) had post-shock EMD, 17 (25%) had VT/VF uncorrected by shocks, 11 (16%) had primary electromechanical dissociation, 9 (13%) had incessant VT/VF, 5 (7%) had VT/VF after their ICD was deactivated or removed, and 6 (9%) had single instances of various other terminal events. Only New York Heart Association functional class independently predicted SD by post-shock EMD.

CONCLUSIONS

The most common mechanism of SD in patients with an ICD is VT/VF treated with an appropriate shock followed by EMD. As this mechanism accounted for 29% of the SDs to which a cause could be ascribed, this mechanism of SD warrants further investigation.

Role of Antiarrhythmic Therapy in Patients at Risk for Sudden Cardiac Death: An Evidence-Based Review

Sudden cardiac death (SCD) accounts for more than half of all cardiac deaths occurring each year in the United States. Although it has several causes, patients at greatest risk are those with coronary artery disease and impaired left ventricular function, heart failure secondary to ischemia or idiopathic dilated cardiomyopathy, hypertrophic cardiomyopathy, documented sustained ventricular tachycardia or ventricular fibrillation, and survivors of cardiac arrest. The presence of asymptomatic ventricular arrhythmias, positive signal-averaged electrocardiogram (ECG), low heart rate variability index, or inducible ventricular tachycardia or ventricular fibrillation increases the risk. In primary prevention trials in patients with ischemic heart disease, beta-blockers reduced both total mortality and SCD, whereas class I antiarrhythmic drugs, especially class IC, increased mortality. Among class III agents, d,l-sotalol and dofetilide have a neutral effect on mortality, whereas d-sotalol increases mortality. Amiodarone has a neutral effect on total and cardiac mortality but does reduce the risk of arrhythmic death and cardiac arrest. Three primary prevention trials in patients with ischemic heart disease were conducted with implantable cardioverter-defibrillators (ICDs). Patients with low ejection fractions (EFs), asymptomatic ventricular arrhythmias, and inducible ventricular tachycardia or ventricular fibrillation had significant reductions in total, cardiac, and arrhythmic death with ICDs compared with either no drug therapy or conventional antiarrhythmic agents. The ICDs did not reduce mortality in patients with low EFs and a positive signal-averaged ECG undergoing coronary bypass graft. In those with heart failure, beta-blockers reduced total and SCD mortality, but dofetilide and amiodarone had a neutral effect on mortality. In the secondary prevention of SCD, antiarrhythmic drugs alone generally are not thought to improve survival. In three trials in patients with documented sustained ventricular tachycardia or ventricular fibrillation, or survivors of SCD, ICDs reduced cardiac and arrhythmic mortality. Total mortality, however, was significantly reduced in only one of these trials. The role of antiarrhythmic drugs in secondary prevention of SCD is limited to patients in whom ICD is inappropriate or in combination with ICD. Antiarrhythmics can be given selectively with ICDs to decrease episodes of ventricular tachycardia or fibrillation to reduce ICD discharges, to suppress episodes of nonsustained ventricular tachycardia that trigger ICD discharges, to slow the rate of ventricular tachycardia to increase hemodynamic stability, to allow effective antitachycardia pacing, or to suppress supraventricular arrhythmias.

Number needed to treat: caveat emptor

Number needed to treat (NNT)-the inverse of the absolute risk reduction resulting from an intervention-was introduced as a yardstick to describe the harm as well as the benefit of therapeutic maneuvers. Analysis using NNT works well when comparing two or more interventions that have their impact over the same period of time in similar populations or patients. Under other conditions, however, analysis based on NNT can produce results that diverge widely from the impact that the interventions can be expected to have on risk of death. This can happen either for entire populations or for an individual when comparing NNTs for interventions which have their effects on different subsets of the population or when comparing interventions which have their effects over different periods of time. We demonstrate how this can occur by comparing the NNTs and effect of intervention on deaths in a population for automatic implantable cardioverter defibrillators (AICDs), heart transplantation, and cholesterol lowering through nutritional intervention with plant stanol ester.

Perspectives: does amiodarone increase non-sudden deaths? If so, why?

Despite the antiarrhythmic efficacy of amiodarone, a definitive correlation between amiodarone treatment and increased non-arrhythmic mortality in patients with heart failure and depressed ventricular function has been reported. Results from research in the field of cardiac resynchronization therapy in heart failure may provide some explanations to this observation. We discussed the hypothetical link between amiodarone and non-arrhythmic mortality, which might have a cause--effect relationship, based on cardiac electromechanical disarrangement provoked by electrophysiological properties of amiodarone.

Randomized comparison of antiarrhythmic drug therapy with implantable defibrillators in patients resuscitated from cardiac arrest : the Cardiac Arrest Study Hamburg (CASH)

BACKGROUND

We conducted a prospective, multicenter, randomized comparison of implantable cardioverter-defibrillator (ICD) versus antiarrhythmic drug therapy in survivors of cardiac arrest secondary to documented ventricular arrhythmias.

METHODS AND RESULTS

From 1987, eligible patients were randomized to an ICD, amiodarone, propafenone, or metoprolol (ICD versus antiarrhythmic agents randomization ratio 1:3). Assignment to propafenone was discontinued in March 1992, after an interim analysis conducted in 58 patients showed a 61% higher all-cause mortality rate than in 61 ICD patients during a follow-up of 11.3 months. The study continued to recruit 288 patients in the remaining 3 study groups; of these, 99 were assigned to ICDs, 92 to amiodarone, and 97 to metoprolol. The primary end point was all-cause mortality. The study was terminated in March 1998, when all patients had concluded a minimum 2-year follow-up. Over a mean follow-up of 57+/-34 months, the crude death rates were 36.4% (95% CI 26.9% to 46.6%) in the ICD and 44.4% (95% CI 37.2% to 51.8%) in the amiodarone/metoprolol arm. Overall survival was higher, though not significantly, in patients assigned to ICD than in those assigned to drug therapy (1-sided P=0.081, hazard ratio 0.766, [97.5% CI upper bound 1.112]). In ICD patients, the percent reductions in all-cause mortality were 41.9%, 39.3%, 28. 4%, 27.7%, 22.8%, 11.4%, 9.1%, 10.6%, and 24.7% at years 1 to 9 of follow-up.

CONCLUSIONS

During long-term follow-up of cardiac arrest survivors, therapy with an ICD is associated with a 23% (nonsignificant) reduction of all-cause mortality rates when compared with treatment with amiodarone/metoprolol. The benefit of ICD therapy is more evident during the first 5 years after the index event.

Advantages and disadvantages of trial designs: a review of analysis methods for ICD studies. AVID Investigators

General modalities of analyses that have been used for ICD studies are reviewed. Published "typical" examples are briefly described. The historical cohort method is exemplified with previously unpublished data from the Seattle Cardiac Arrest Survivor database. The AVID Study database is used to compare the results obtained from nonrandomized methodologies with randomized methodologies. Particular issues related to the use of the ICD for example, mode of death, inability to blind, selection practice, and treatment decision times make this a natural pedagogic platform.

Large clinical trials in the management of ventricular arrhythmias. Applying group results to individual cases

Applying the results of clinical trials to everyday practice in an appropriate manner can be difficult. Earlier clinical trials focused on the secondary prevention of ventricular arrhythmias. Studying patients at high risk of recurrent ventricular arrhythmias is important, but the overall impact on arrhythmic death is low. Recent arrhythmia trials have studied specific patient populations for the primary prevention of ventricular arrhythmias. New trials will expand the investigation to other populations. This article summarizes the results of large clinical trials in the management of ventricular arrhythmias and attempts to provide guidelines for applying their results to everyday clinical practice.

The implantable cardioverter-defibrillator

Ventricular arrhythmias remain a major cause of cardiovascular mortality. Therapy for serious ventricular arrhythmias has evolved over the past decade, from treatment primarily with antiarrhythmic drugs to implanted devices. The implantable cardioverter-defibrillator (ICD) is the best therapy for patients who have experienced an episode of ventricular fibrillation not accompanied by an acute myocardial infarction or other transient or reversible cause. It is also superior therapy in patients with sustained ventricular tachycardia (VT) causing syncope or hemodynamic compromise. Controlled clinical trials have confirmed the utility of these devices. As primary prevention, the ICD is superior to conventional antiarrhythmic drug therapy in patients who have survived a myocardial infarction and who have spontaneous, nonsustained ventricular tachycardia, a low ejection fraction, inducible VT at electrophysiologic study, and whose VT is not suppressed by procainamide. The effect of the ICD on survival of other patient populations remains to be proven. The device is costly, but its price is generally accepted to be reasonable. The ICD has been a major advance in the treatment of ventricular arrhythmias.

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.

Management of ventricular arrhythmias: a trial-based approach

Sudden cardiac death accounts for approximately 300,000 deaths annually in the U.S., and most of these are secondary to ventricular tachycardia (VT) and fibrillation in patients with coronary artery disease. Most patients with cardiac death die before reaching the hospital, which brought about a tremendous amount of research focused at identifying patients at high risk. Several trials were initiated to test the effectiveness of various therapeutic measures in these high-risk patients. A history of myocardial infarction, depressed left ventricular function and nonsustained VT have all been identified as independent risk factors for future arrhythmic death. Similarly, patients with a history of sustained VT or a history of sudden cardiac death are a high-risk group and should be aggressively evaluated and treated. The purpose of this article is to discuss risk stratification and primary prevention of sustained ventricular arrhythmias. We also review the recent secondary prevention trials and discuss the options available in the management of patients with sustained ventricular arrhythmias.

Sudden Electrical Death

Survivors of an episode of out-of-hospital ventricular fibrillation (not due to a reversible cause) or hemodynamically significant sustained ventricular tachycardia should in most cases receive an implantable cardioverter defibrillator (ICD) rather than antiarrhythmic drug therapy. A number of recently published clinical trials (summarized later) point to improved survival with ICD implantation. It is also important to identify the cause of the ventricular rhythm and to treat adequately the underlying cardiomyopathy with the appropriate angiotensin-converting enzyme (ACE) inhibitors, beta-blockers, and aspirin. The role of electrophysiologic study is a matter of debate, and it is used less commonly than it was a decade ago.

Comparison of the long-term efficacy of implantable defibrillators and sotalol for documented spontaneous sustained ventricular tachyarrhythmias secondary to coronary artery disease

BACKGROUND

The relative efficacy of antitachycardia pacing implantable cardioverter defibrillators (ATPICD) and sotalol in the treatment of ventricular tachyarrhythmias is controversial.

AIM

To compare the mortality in patients treated with ATPICD and sotalol for documented spontaneous sustained ventricular tachyarrhythmias occurring late after previous myocardial infarction.

METHODS

In this non-randomised retrospective study of 139 consecutive patients all patients had inducible ventricular tachycardia at baseline electrophysiological studies. Before the availability of ATPICD, 22 patients were treated with sotalol as part of a randomised study comparing the efficacy of sotalol to amiodarone. After ATPICD became available sotalol was used in 49 patients in whom intravenous testing predicted sotalol to be effective and ATPICD were implanted in 68 patients in whom sotalol was predicted to be ineffective at electrophysiological testing. Thus, 68 patients were treated with an ATPICD and 71 with sotalol.

RESULTS

The two groups were well-matched for age, type of presenting arrhythmia, severity of coronary artery disease and ventricular function. At 36 months Kaplan-Meier estimates of mortality from ventricular tachyarrhythmia were 0% with ATPICD and 15% with sotalol (p=0.03). Kaplan-Meier estimates of total mortality at 36 months were 12% with ATPICD and 25% with sotalol (p=0.09). Multivariate analysis showed hazard ratio of 7.9 (p=0.06) for death from ventricular tachyarrhythmia in patients treated with sotalol compared to ATPICD.

CONCLUSIONS

While no difference in total mortality was demonstrated, treatment with ATPICD is probably superior to sotalol for preventing deaths due to ventricular tachyarrhythmia.

Navigation in the mega-trials waters: reflections on the Multicenter Automatic Defibrillator Implantation Trial and the Antiarrhythmics Versus Implantable Defibrillators Study

Today, cardiology seems to be driven by mega-trials and meta-analyses. Guidelines published by scientific and professional cardiovascular societies, such as the American Heart Association, the American College of Cardiology, and the European Society of Cardiology, follow the rules of evidence-based medicine. Such evidence is not always sufficiently conclusive to practice clinically helpful medicine. Sometimes, relatively small trials, such as the Multicenter Automatic Defibrillator Implantation Trial and the Antiarrhythmics Versus Implantable Defibrillators study, may be taken as guides for current clinical decisions and as inspiration for future investigations. Large mega-trials with a great lack of homogeneity among the recruited patients are less important for clinically helpful medicine than studies enrolling well-defined, high-risk patients. It is probably important to acknowledge that the best possible treatment for many patients with ventricular tachyarrhythmias remains obscure. Among these situations are the following: (1) sustained ventricular tachycardia (VT) in patients without coronary artery disease; (2) sustained, nonsyncopal VT in patients with coronary artery disease and left ventricular dysfunction; (3) post myocardial infarction survivors with an ejection fraction < or = 35%, frequent/complex ventricular arrhythmias, depressed heart rate variability, and inducible sustained ventricular tachyarrhythmias during electrophysiologic study. Many studies are being conducted to add light where uncertainty exists, but probably only a few will contribute to the practice of clinically helpful medicine, although some will be used to produce meta-analysis to sustain evidence-based medicine.

Secondary prevention of sudden death: the Dutch Study, the Antiarrhythmics Versus Implantable Defibrillator Trial, the Cardiac Arrest Study Hamburg, and the Canadian Implantable Defibrillator Study

Although indisputably effective in the prevention of sudden death, use of implantable cardioverter defibrillator (ICD) therapy may not necessarily affect all-cause mortality, as most patients at risk also present with severely depressed left ventricular dysfunction. Correction of the sudden death risk in these patients creates a new clinical condition in need of a careful assessment. Should all-cause mortality be affected by the expected reduction in sudden death rate associated with ICD therapy, issues of critical importance, such as the time extent of life prolongation and the associated quality of life, still remain to established. To investigate the potential benefit of ICD therapy compared with antiarrhythmic drug treatment, 4 prospective studies--the Dutch trial, the Antiarrhythmics Versus Implantable Defibrillators (AVID) study, the Cardiac Arrest Study Hamburg (CASH), and the Canadian Implantable Defibrillator Study (CIDS)--have been conducted in which patients with documented sustained ventricular arrhythmia were randomized to 1 of these 2 treatment strategies. The enrollment criteria differed in these 4 studies: (1) in the Dutch trial, they included cardiac arrest secondary to a ventricular arrhythmia, old (> 4 weeks) myocardial infarction, and inducible ventricular arrhythmia; (2) in AVID and CIDS, ventricular fibrillation or poorly tolerated ventricular tachycardia; and (3) in CASH, cardiac arrest secondary to a ventricular arrhythmia regardless of the underlying disease. With regard to the antiarrhythmic drugs, the Dutch trial tested class I and III agents, whereas AVID and CIDS compared ICD therapy with class III agents (mostly amiodarone). In CASH, 3 drug subgroups were investigated: propafenone, amiodarone, and metoprolol. All trials used all-cause mortality as the primary endpoint. Data from these trials provide support for ICD as a therapy superior to antiarrhythmic drugs in prolonging survival in patients meeting the entry criteria. This review briefly summarizes the methods, results, limitations, and clinical implications of these 4 studies.

Antiarrhythmic drugs or implantable cardioverter defibrillators in heart failure: the "poor heart"

Ventricular tachycardia and ventricular fibrillation account for a substantial proportion of all deaths in patients with heart failure. Of currently available therapies, amiodarone and the implantable cardioverter defibrillator (ICD) appear to have the greatest potential to decrease sudden death in heart failure. In this article, the presently available information on the relative role of antiarrhythmic drugs, with a focus on amiodarone and ICDs in heart failure, is reviewed.

The implantable cardioverter defibrillator as a "bridge to transplant": a viable clinical strategy?

Heart transplantation is an accepted therapeutic option for patients with end-stage heart disease. However, because the availability of heart donors fails to keep pace with the growing demand, increasing numbers of potential recipients are placed on the waiting list, resulting in longer waiting times. About 20% of patients die while awaiting heart transplantation. The majority die from progressive pump failure (46%), whereas about 30% of all deaths occur suddenly. Monitored terminal cardiac electrical activity in patients dying while awaiting transplantation reveals that bradyarrhythmias and/or electromechanical dissociation are involved in 68% of cases and ventricular tachyarrhythmias in 32% of cases. Patients with a history of aborted cardiac arrest are at highest risk for recurrent malignant arrhythmias. The implantable cardioverter defibrillator (ICD) is the most effective therapy for preventing sudden cardiac death from ventricular tachyarrhythmias. Pooled data from a total of 75 sudden death survivors listed for cardiac transplantation demonstrate that ICD therapy can be applied with low mortality, low morbidity, and high efficacy, with up to 94% of the patients receiving appropriate shocks during the waiting period. However, there is considerable concern that this early survival benefit conferred by the ICD may be nullified by the competing risk of death due to terminal pump failure, as the waiting list and waiting time to transplantation lengthens. In advanced heart failure, risk stratification for sudden tachyarrhythmic death is only of limited value. Therefore, although sudden tachyarrhythmic death appears to constitute only a minor fraction of total cardiac death in patients awaiting heart transplantation, prophylactic ICD implantation as on electronic bridge to transplant may be considered. To define conclusively the role of prophylactic ICD therapy in this setting, prospective randomized studies are needed.

Can implantable defibrillators reduce non-arrhythmic mortality?

Several authors have made the intriguing observation that Implantable Cardioverter Defibrillators (ICD) appear not only to reduce sudden deaths, but also mortality due to non-arrhythmic causes. Studies have shown that this observation can not be attributed to patient selection bias. In trying to explain this apparent anomaly, it should be noted that two treatment strategies are being compared. Thus, it might be that, under certain circumstances, antiarrhythmic drugs contribute to non-arrhythmic deaths, not that ICDs reduce them. There appear to be some plausible explanations for this phenomenon, e.g., the long-term effect on cardiac function of episodes of ventricular tachycardia lasting for several hours for patients treated solely by antiarrhythmic drugs, compared to their quick termination by an ICD. However, further research into this curious mode of death issue is needed, and may provide further insights into patient populations deriving greatest benefit from one therapy or the other.

The search for novel antiarrhythmic strategies. Sicilian Gambit

The past fifty years of antiarrhythmic drug development have seen limited success in prolonging life and reducing morbidity. It is likely that arrhythmias are in most instances final common pathways through which changes in the cardiac substrate and in trigger mechanisms are expressed. We propose that the development and administration of therapies for the arrhythmias themselves, while offering a panacea for a disease entity that has evolved and is being overtly manifested, is also an admission of failure to identify and prevent evolution of the substrate and triggers such that arrhythmias can occur. We suggest that while strategies for treatment and prevention of recurrence of arrhythmias still warrant exploration, greater hope for the future lies in identifying means for earlier diagnosis of the arrhythmogenic substrate and triggers, and in developing therapies that are "upstream" to the arrhythmia and prevent their initial expression. Means to achieve this end are suggested, using specific arrhythmias as examples. Similarly, to increase the likelihood that clinical studies of new therapies can be successfully concluded and interpreted, we suggest new approaches to patient selection, risk stratification, trial endpoints, outcome events and trial methodologies.

Antiarrhythmic drugs and devices for the management of ventricular tachyarrhythmia in ischemic heart disease

Ischemic heart disease is the most frequent cardiac abnormality in patients with sustained or nonsustained ventricular tachyarrhythmias. The goals of therapy in such patients are to decrease the severity and incidence of symptoms and prolong life. In this article, we review the current views on antiarrhythmic drug therapy and an implantable cardioverter-defibrillator (ICD) in patients with ischemic heart disease. The importance of beta blockade as part of the therapy is emphasized. In addition, the superiority of sotalol and amiodarone over class I drugs, the benefits of combined treatment with amiodarone and a beta blocker, and the impact and limitations of current trials comparing the effectiveness of drug therapy with that of an ICD are all considered. Also discussed is the combined use of an antiarrhythmic drug and an ICD. In this approach sotalol is generally the agent of choice, with amiodarone the second choice.

A decade of clinical trial developments in postmyocardial infarction, congestive heart failure, and sustained ventricular tachyarrhythmia patients: from CAST to AVID and beyond. Cardiac Arrhythmic Suppression Trial. Antiarrhythmic Versus Implantable Defibrillators

Multiple trials using antiarrhythmic drugs, pharmacologic therapy, and implantable cardioverter defibrillators have been performed in an attempt to improve survival in patients: (1) postmyocardial infarction; (2) with congestive heart failure, with and without nonsustained ventricular tachycardia; and (3) with sustained ventricular tachycardia and those who have survived an out-of-hospital cardiac arrest. This article reviews some of the key findings and limitations of completed and ongoing trials. We also make recommendations for the current treatment of such patients based on the results of these trials.

Causes and consequences of discontinuation of the implantable cardioverter-defibrillator therapy in non-terminally ill patients

Infection and implantable cardioverter-defibrillator shocks are important contributing factors to discontinuation of cardioverter-defibrillator therapy in non-terminally ill patients. These patients are at a high risk of sudden cardiac death despite continued antiarrhythmic drug therapy.

[Current indications for implantable automatic defibrillators]

Since the first implantation in man in 1980 implantable cardioverter defibrillator technology has greatly improved and the number of devices implanted has increased considerably in recent years. Non-thoracotomy lead systems and biphasic shocks are now the approach of choice, offering nearly a 100% success rate. This paper version reviews the current indications for the implantation of implantable cardioverter defibrillator and is an upgraded of an article previously published by the Arrhythmia's Section of the Spanish Society of Cardiology. Recommendations for qualification of centres implanting defibrillators and follow up are also addressed.

On the necessity of the invasive predischarge test after implantation of a cardioverter-defibrillator

The necessity of routine invasive implantable cardioverter-defibrillator (ICD) testing before hospital discharge was analyzed in 268 patients. In 98% of the patients, invasive ICD testing was not necessary if a preimplant electrophysiologic test was performed; most of the observed problems can be solved by noninvasive control.

Primary prevention of sudden cardiac death in heart failure: will the solution be shocking?

Sudden cardiac death (SCD) may occur in as many as 40% of all patients who suffer from heart failure. This review describes the scope of the problem, risk factors for SCD, the effect of medications used in heart failure on SCD and the potential effect of the implantable cardioverter-defibrillator in primary prevention.

A comparison of antiarrhythmic-drug therapy with implantable defibrillators in patients resuscitated from near-fatal ventricular arrhythmias

BACKGROUND

Patients who survive life-threatening ventricular arrhythmias are at risk for recurrent arrhythmias. They can be treated with either an implantable cardioverter-defibrillator or antiarrhythmic drugs, but the relative efficacy of these two treatment strategies is unknown.

METHODS

To address this issue, we conducted a randomized comparison of these two treatment strategies in patients who had been resuscitated from near-fatal ventricular fibrillation or who had undergone cardioversion from sustained ventricular tachycardia. Patients with ventricular tachycardia also had either syncope or other serious cardiac symptoms, along with a left ventricular ejection fraction of 0.40 or less. One group of patients was treated with implantation of a cardioverter-defibrillator; the other received class III antiarrhythmic drugs, primarily amiodarone at empirically determined doses. Fifty-six clinical centers screened all patients who presented with ventricular tachycardia or ventricular fibrillation during a period of nearly four years. Of 1016 patients (45 percent of whom had ventricular fibrillation, and 55 percent ventricular tachycardia), 507 were randomly assigned to treatment with implantable cardioverter-defibrillators and 509 to antiarrhythmic-drug therapy. The primary end point was overall mortality.

RESULTS

Follow-up was complete for 1013 patients (99.7 percent). Overall survival was greater with the implantable defibrillator, with unadjusted estimates of 89.3 percent, as compared with 82.3 percent in the antiarrhythmic-drug group at one year, 81.6 percent versus 74.7 percent at two years, and 75.4 percent versus 64.1 percent at three years (P<0.02). The corresponding reductions in mortality (with 95 percent confidence limits) with the implantable defibrillator were 39+/-20 percent, 27+/-21 percent, and 31+/-21 percent

CONCLUSIONS

Among survivors of ventricular fibrillation or sustained ventricular tachycardia causing severe symptoms, the implantable cardioverter-defibrillator is superior to antiarrhythmic drugs for increasing overall survival.

Baseline characteristics of patients in the coronary artery bypass graft (CABG) Patch Trial

BACKGROUND

Patients with left ventricular dysfunction who undergo coronary artery bypass graft (CABG) surgery frequently have late sudden cardiac death. The CABG Patch Trial is a prospective, randomized, multicenter clinical trial that randomized patients at high risk at the completion of CABG surgery to implantation of an epicardial implantable cardioverter defibrillator (ICD) or to no antiarrhythmic treatment. The trial was designed to determine whether prophylactic implantation of an ICD at the time of CABG surgery would result in a lower total mortality in long-term follow-up.

METHODS

Patients undergoing CABG surgery were eligible for the trial if they were younger than 80 years, had a left ventricular ejection fraction less than 0.36, and had an abnormal signal averaged electrocardiogram. Patients with a history of sustained ventricular tachycardia or ventricular fibrillation were excluded from the trial. All patients were scheduled to undergo follow-up at 3-month intervals until 42 months after surgery.

RESULTS

Randomization of patients in the trial ended in February 1996. During the recruitment period 71,855 patients were screened, 1,422 were eligible, 1,055 were enrolled (signed consent forms), and 900 patients (76% of eligible patients) were randomized. The mean age of the 446 patients in the ICD group was 64 years versus 63 years for the 454 patients in the control group. A total of 87% of the participants in the ICD group were men versus 82% in the control group (p = NS). Most of the patients had a history of hypertension (55%), smoking (78%), and hypercholesterolemia (54%). Half of the patients had clinical heart failure, and the mean ejection fraction for both patient groups was 0.27 +/- 0.06. No difference was seen in the history of myocardial infarction (83%), congestive heart failure (50%), or atrial (11%) or ventricular (17%) arrhythmias between the two groups. Major clinical characteristics (age, sex, number of previous infarctions, incidence of heart failure, and mean left ventricular ejection fraction) were almost identical to those found in another ICD primary prevention trial, the Multicenter Automatic Defibrillator Implantation Trial (MADIT).

CONCLUSIONS

A high risk sample of patients was enrolled in The CABG Patch Trial, as shown by examination of their baseline characteristics.

Antiarrhythmic therapy--future trends and forecast for the 21st century

This article discusses recent changes in antiarrhythmic therapy, with a focus on nonpharmacologic therapy (electrode catheter ablation, implantable cardioverter-defibrillators [ICDs]), and puts them into perspective for the coming years. The treatment of supraventricular tachycardias and tachycardia involving accessory pathways is likely to remain the domain of catheter ablation. With promising new techniques under investigation, the spectrum of arrhythmias that can be cured will probably be expanded. Treatment of life-threatening ventricular arrhythmias is likely to remain the domain of the ICD in the foreseeable future. With the safety net of the ICD in place, new antiarrhythmic drugs or other forms of antiarrhythmic therapy can be developed and tested.

Drugs versus devices in controlling ventricular tachycardia, ventricular fibrillation, and recurrent cardiac arrest

Patients with symptomatic ventricular tachycardia, ventricular fibrillation, or aborted sudden cardiac death remain at high risk for arrhythmia recurrence. In recent years, strategies to treat these patients have changed. Concerns about the proarrhythmia risk and uncertain efficacy of class I agents have resulted in a shift in interest to non-class I antiarrhythmic drugs such as sotalol and amiodarone. Both drugs have class III antiarrhythmic properties (i.e., both lengthen repolarization and refractoriness); however, each also has its own additional electrophysiologic effects. Prospectively designed, randomized studies have shown that both sotalol and amiodarone have more potent antiarrhythmic actions than class I agents. However, even as the advantages of sotalol and amiodarone have been recognized, enthusiasm for nonpharmacologic modes of treatment, particularly the implantable cardioverter-defibrillator (ICD), has also markedly increased. The ICD has been shown to decrease dramatically the incidence of sudden death, which may lead to the reduction of total mortality. Whether patients with life-threatening ventricular tachyarrhythmias should be treated first with antiarrhythmic agents or with an ICD is an important question. The results of recent studies suggest that treatment with an ICD is more effective than electrophysiologically guided treatment with class I agents. However, results of prospectively designed randomized studies comparing the efficacy of the ICD with that of sotalol and amiodarone must become available before definitive recommendations can be made concerning the use of the ICD as first-line therapy in patients with ventricular tachycardia/ventricular fibrillation or aborted sudden cardiac death. In addition, there may be a significant role for the use of antiarrhythmic drugs in conjunction with ICDs.