Canadian Implantable Defibrillator Study (CIDS): study design and organization. CIDS Co-Investigators

Multiparameter Monitoring with a Wearable Cardioverter Defibrillator

A wearable cardioverter-defibrillator (WCD) is a temporary treatment option for patients at high risk for sudden cardiac death (SCD) and for patients who are temporarily not candidates for an implantable cardioverter defibrillator (ICD). In addition, the need for telemedical concepts in the detection and treatment of heart failure (HF) and its arrhythmias is growing. The WCD has evolved from a shock device detecting malignant ventricular arrhythmias (VA) and treating them with shocks to a heart-failure-monitoring device that captures physical activity and cardioacoustic biomarkers as surrogate parameters for HF to help the treating physician surveil and guide the HF therapy of each individual patient. In addition to its important role in preventing SCD, the WCD could become an important tool in heart failure treatment by helping prevent HF events by detecting imminent decompensation via remote monitoring and monitoring therapy success.

Implantable cardioverter defibrillators for the treatment of arrhythmias and cardiac resynchronisation therapy for the treatment of heart failure: systematic review and economic evaluation

BACKGROUND

This assessment updates and expands on two previous technology assessments that evaluated implantable cardioverter defibrillators (ICDs) for arrhythmias and cardiac resynchronisation therapy (CRT) for heart failure (HF).

OBJECTIVES

To assess the clinical effectiveness and cost-effectiveness of ICDs in addition to optimal pharmacological therapy (OPT) for people at increased risk of sudden cardiac death (SCD) as a result of ventricular arrhythmias despite receiving OPT; to assess CRT with or without a defibrillator (CRT-D or CRT-P) in addition to OPT for people with HF as a result of left ventricular systolic dysfunction (LVSD) and cardiac dyssynchrony despite receiving OPT; and to assess CRT-D in addition to OPT for people with both conditions.

DATA SOURCES

Electronic resources including MEDLINE, EMBASE and The Cochrane Library were searched from inception to November 2012. Additional studies were sought from reference lists, clinical experts and manufacturers' submissions to the National Institute for Health and Care Excellence.

REVIEW METHODS

Inclusion criteria were applied by two reviewers independently. Data extraction and quality assessment were undertaken by one reviewer and checked by a second. Data were synthesised through narrative review and meta-analyses. For the three populations above, randomised controlled trials (RCTs) comparing (1) ICD with standard therapy, (2) CRT-P or CRT-D with each other or with OPT and (3) CRT-D with OPT, CRT-P or ICD were eligible. Outcomes included mortality, adverse events and quality of life. A previously developed Markov model was adapted to estimate the cost-effectiveness of OPT, ICDs, CRT-P and CRT-D in the three populations by simulating disease progression calculated at 4-weekly cycles over a lifetime horizon.

RESULTS

A total of 4556 references were identified, of which 26 RCTs were included in the review: 13 compared ICD with medical therapy, four compared CRT-P/CRT-D with OPT and nine compared CRT-D with ICD. ICDs reduced all-cause mortality in people at increased risk of SCD, defined in trials as those with previous ventricular arrhythmias/cardiac arrest, myocardial infarction (MI) > 3 weeks previously, non-ischaemic cardiomyopathy (depending on data included) or ischaemic/non-ischaemic HF and left ventricular ejection fraction ≤ 35%. There was no benefit in people scheduled for coronary artery bypass graft. A reduction in SCD but not all-cause mortality was found in people with recent MI. Incremental cost-effectiveness ratios (ICERs) ranged from £14,231 per quality-adjusted life-year (QALY) to £29,756 per QALY for the scenarios modelled. CRT-P and CRT-D reduced mortality and HF hospitalisations, and improved other outcomes, in people with HF as a result of LVSD and cardiac dyssynchrony when compared with OPT. The rate of SCD was lower with CRT-D than with CRT-P but other outcomes were similar. CRT-P and CRT-D compared with OPT produced ICERs of £27,584 per QALY and £27,899 per QALY respectively. The ICER for CRT-D compared with CRT-P was £28,420 per QALY. In people with both conditions, CRT-D reduced the risk of all-cause mortality and HF hospitalisation, and improved other outcomes, compared with ICDs. Complications were more common with CRT-D. Initial management with OPT alone was most cost-effective (ICER £2824 per QALY compared with ICD) when health-related quality of life was kept constant over time. Costs and QALYs for CRT-D and CRT-P were similar. The ICER for CRT-D compared with ICD was £27,195 per QALY and that for CRT-D compared with OPT was £35,193 per QALY.

LIMITATIONS

Limitations of the model include the structural assumptions made about disease progression and treatment provision, the extrapolation of trial survival estimates over time and the assumptions made around parameter values when evidence was not available for specific patient groups.

CONCLUSIONS

In people at risk of SCD as a result of ventricular arrhythmias and in those with HF as a result of LVSD and cardiac dyssynchrony, the interventions modelled produced ICERs of < £30,000 per QALY gained. In people with both conditions, the ICER for CRT-D compared with ICD, but not CRT-D compared with OPT, was < £30,000 per QALY, and the costs and QALYs for CRT-D and CRT-P were similar. A RCT comparing CRT-D and CRT-P in people with HF as a result of LVSD and cardiac dyssynchrony is required, for both those with and those without an ICD indication. A RCT is also needed into the benefits of ICD in non-ischaemic cardiomyopathy in the absence of dyssynchrony.

STUDY REGISTRATION

This study is registered as PROSPERO number CRD42012002062.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

State of the art of ICD programming: Lessons learned and future directions

The lifesaving benefits of implantable cardioverter defibrillator (ICD) therapy are more and more weighted against possible harm (e.g. unnecessary device therapy, procedural complications, device malfunction etc.) which might have adverse effects on patients' perceived health status and quality of life. Hence, there has been an increasing interest in the optimisation of ICD programming to prevent inappropriate and appropriate but unnecessary device therapy. The purpose of the current report is to give an overview of research into the optimisation of ICD programming and present the design of the on-going ENHANCED-ICD study. The ENHANCED-ICD study is a prospective, safety monitoring study enrolling 60 primary and secondary prophylactic ICD patients at the University Medical Center Utrecht. Patients implanted with any type of ICD with SmartShock technology(TM), and between 18-80 years of age, were eligible to participate. In all patients a prolonged detection of 60/80 intervals was programmed. The primary objective of the study is to investigate whether enhanced programming to further reduce ICD therapies is safe. The secondary objective is to examine the impact of enhanced programming on (i) antitachycardia pacing and shocks (both appropriate and inappropriate) and (ii) quality of life and distress. The first results of the ENHANCED-ICD study are expected in 2015.

Strategies for the prevention and treatment of sudden cardiac death

Cardiovascular diseases account for 40% of all deaths in the West. Sudden cardiac death (SCD) is a major health problem affecting over 300,000 patients annually in the United States alone. Presence of coronary artery disease (CAD), usually in the setting of diminished left ventricular ejection fraction, is still the single major risk factor for SCD. Additionally, acute myocardial ischemia, structural cardiac defects, anomalous coronary arteries, cardiomyopathies, genetic mutations, and ventricular arrhythmias are all attributed to SCD, demonstrating the perplexity of this condition. With the recent advancements in cardiovascular medicine, the incidence of SCD is expected to increase steeply as the prevalence of CAD and heart failure is uprising in general population. Considering SCD, the major challenge confronting contemporary cardiology, multiple strategies for prevention against SCD have been developed. β-blockers have been shown to reduce the risk of SCD, whereas implantable cardioverter-defibrillator devices are found to be effective at terminating the malignant arrhythmias. In recent years, multiple clinical trials were carried out to identify patients who may benefit from preventive intervention, including medical therapy and automatic cardioverter-defibrillator implantations. This review article provides insight into the advanced strategies for the prevention and treatment of SCD based on the data available in medical literature to date.

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 cardioverter defibrillator discharge rates in patients with unexplained syncope, structural heart disease, and inducible ventricular tachycardia at electrophysiologic study

BACKGROUND AND HYPOTHESIS

The implantable cardioverter defibrillator (ICD) is the best available strategy to protect patients from life-threatening ventricular arrhythmia. Although unproven, it is commonly utilized to treat subjects with syncope, a negative clinical workup, structural heart disease, and inducible sustained monomorphic ventricular tachycardia (VT) on programmed electrophysiologic stimulation (EPS). The purpose of this paper was to validate this approach.

METHODS

We retrospectively identified 36 subjects who received primary ICD therapy for syncope in the setting of structural heart disease with inducible sustained monomorphic VT on EPS. The cohort was predominantly male (32/36) with underlying coronary artery disease (29/36). The mean left ventricular ejection fraction was 31 +/- 12%, and a third of the patients (12/36) had undergone bypass surgery.

RESULTS

The study group was followed for a mean of 23 +/- 15 months (range 3-81 months) and experienced an ICD event rate of 22% at 3 months, which increased to 55% at 36 months. This event rate was comparable with the 66% event rate seen in a group of patients with primary ICD therapy for spontaneous life-threatening VT treated during the same time period. No future predictors of ICD events in the study group could be identified.

CONCLUSION

Syncope patients with negative workup, structural heart disease, and sustained monomorphic VT at EPS are at high risk for future tachyarrhythmic events. Based on present evidence, primary ICD therapy in this group appears warranted and justified.

Amiodarone: what have we learned from clinical trials?

Amiodarone is an antiarrhythmic agent commonly used in the treatment of supraventricular and ventricular tachyarrhythmias. This paper reviews clinical trials in which amiodarone was used in one of the treatment arms. Key post-myocardial infarction trials include EMIAT and CAMIAT, both of which demonstrated that amiodarone reduced arrhythmic but not overall mortality. In patients with congestive heart failure (CHF), amiodarone was associated with a neutral survival in CHF/STAT and improvement in survival in GESICA. In patients with nonsustained ventricular tachycardia, the MADIT trial demonstrated that therapy with an implantable cardioverter-defibrillator (ICD) improved survival compared with the antiarrhythmic drug arm in such patients, most of whom were taking amiodarone. In sustained VT/VF patients, the CASCADE trial demonstrated that empiric amiodarone lowered arrhythmic recurrence rates compared with other drugs guided by serial Holter or electrophysiologic studies. Several trials including AVID, CIDS, and CASH have demonstrated the superiority of ICD therapy compared with empiric amiodarone in improving overall survival. Clinical implications of these trials are discussed.

Sustained ventricular tachycardia in apical hypertrophic cardiomyopathy, midcavitary obstruction, and apical aneurysm

The prevalence of hypertrophic cardiomyopathy is estimated at 1:500 in the general population. Of these patients, approximately 1% develops midcavitary obstruction and subsequent apical aneurysm. We present a brief review of the literature on apical hypertrophic cardiomyopathy (HCM) using a rare case-based example. The etiology for apical aneurysm development is unclear but is thought to extend from apical fibrosis and necrosis secondary to subendocardial ischemia. The lifetime risk of cardiovascular death in patients with HCM is 2%. However, the risk may be higher in patients with apical aneurysms. Definitive therapy involves implantation of an automatic implantable cardioverter defibrillator, since medical therapy has variable success.

Prevention of sudden cardiac death

Although the annual incidence of sudden cardiac death (SCD) is dropping in the United States, therapies for the patient who has survived a SCD episode or is at high risk of developing SCD in the future are now well established. The implantable cardioverter defibrillator (ICD) has emerged from a series of well done randomized clinical trials of the 1990s as providing a survival benefit in carefully defined patient groups with low ejection fraction of any cause. Patients with either an ischemic or idiopathic dilated cardiomyopathy and an EF <or=35% show a significant survival benefit with the ICD and maximal medical therapy. Many challenging patients (e.g., those with long QT syndrome or Brugada syndrome) who have a reasonably high incidence of sudden death have not been the subject of clinical trials involving the ICD and therapy depends on risk stratification that is currently not completely agreed upon. An exciting research frontier of the future will be those that attempt to integrate the appropriate role of the ICD with the ability of chronic resynchronization therapy to enhance left ventricular function in the damaged ventricle.

Relationship of the implantable cardioverter defibrillator and chronic resynchronization therapy: the perfect marriage?

BACKGROUND

The two major modes of death in the patient with a reduced ejection fraction (EF) are death due to heart failure and death due to lethal arrhythmia, essentially the two sides of the same coin. Over the last 20 years, two therapies-cardiac resynchronization therapy (CRT) and the implantable cardioverter defibrillator (ICD)-have been developed and tested in clinical trials. They are now, in conjunction with appropriate medical therapy, the mainstays of therapy for these two commonly encountered clinical problems.

METHOD AND RESULTS

Both of these therapies were conceived and patented by two Baltimore cardiologists, Michel Mirowski and Morton Mower (Table I). The path to everyday acceptance of both therapies was remarkably similar. The concept and early success of both devices was accomplished but the proof of concept depended on a series of carefully designed randomized clinical trials that showed that both the CRT and ICD devices saved lives in the low EF population, especially when used together. These trials overcame substantial skepticism on behalf of elements of the cardiology and electrophysiology establishment.

CONCLUSION

We are now at a crossroads in the further extension of either therapy. The majority of the indications for either device alone or in combination are established. In the next few years, assuming the continued commitment on the part of regulatory agencies to fully embrace evidence-based medicine, we will see indications extended but only by the careful clinical trials that became the bedrock of their initial acceptance.

Current role of device therapy to reduce sudden cardiac death in heart failure

Sudden cardiac death (SCD) continues to be a major contributor to mortality in patients with heart failure (HF) despite recent advances in medical therapy. Device therapy, including the implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy (CRT), serves as an adjunct in reducing HF mortality. Several clinical trials support the prophylactic use of the ICD in reducing mortality in certain HF populations and have established the clinical benefits of CRT in advanced HF. More recently, the Comparison of Medical Therapy Pacing and Defibrillation in Heart Failure trial was the first study to demonstrate a survival benefit of CRT alone or in conjunction with an ICD. This article reviews the most pertinent data regarding the role of device therapy in reducing SCD in HF and addresses future challenges faced by device manufacturers and clinicians.

Incidence and electrophysiological characteristics of spontaneous ventricular tachyarrhythmias in high risk coronary patients and prophylactic implantation of a defibrillator

OBJECTIVES

To assess the incidence and electrophysiological characteristics of spontaneous ventricular tachyarrhythmias after implantable cardioverter-defibrillator (ICD) implantation for primary prevention.

DESIGN

Prospective observational study.

PATIENTS

41 consecutive patients, who fulfilled MADIT (multicenter automatic defibrillator implantation trial) I criteria, except for suppressibility by procainamide, and who received a prophylactic ICD.

INTERVENTIONS

Subpectoral implantation of an ICD.

MAIN OUTCOME MEASURES

Incidence of ventricular tachyarrhythmias and their electrophysiological characteristics with respect to timing of the arrhythmia, tachyarrhythmia cycle length, mode of termination, and clinical relevance.

RESULTS

During a mean (SD) follow up of 30 (21) months 18 of 41 (43.9%) patients experienced 142 appropriate ICD treatments. The mean (SD) time to first event was 9.6 (15.1) months. One patient had ventricular fibrillation (VF), 12 patients ventricular tachycardia (VT), and five both VT and VF. The mean (SD) cycle length of monomorphic VT was 306 (42) ms. Of 142 episodes, 117 (82.3%) were terminated by antitachycardia pacing and another 25 (17.6%) by ICD discharges. Cumulative survival of hypothetical death, defined as treated VT with a cycle length < 260 ms or VF, was 83.2% after one year and 78.4% after two years.

CONCLUSIONS

Patients with a left ventricular ejection fraction < 35%, a history of myocardial infarction, non-sustained VT, and inducible VT/VF are at high risk of VT/VF early after implantation. Therefore, implantation of a tiered treatment defibrillator seems to be justified.

Shocks from pacemaker cardioverter defibrillators increase with amiodarone in patients at high risk for sudden cardiac death

The efficacy of amiodarone used in combination with a pacemaker cardioverter defibrillator (PCD) to decrease episodes of ventricular tachycardia and subsequent PCD shocks is not clear. We examined a retrospective registry of 82 patients with PCD implantation to define the efficacy of amiodarone treatment. We compared patients treated with amiodarone (for 24 consecutive months without interruption) versus no amiodarone. In patients treated with amiodarone there was a 3-fold increase (p = 0.02) in PCD shocks; in patients not on beta-blockers, amiodarone resulted in a 6-fold increase (p < 0.05) in PCD shocks. Patients with a left ventricular ejection fraction >30% on amiodarone and patients <72 years old had increases (p < 0.05) in PCD shocks. In conclusion, patients treated with amiodarone had more PCD shocks than those not treated. These findings are unexpected and merit a prospective study.

Arrhythmias in Patients with Heart Failure

Both atrial and ventricular arrhythmias are very common in patients with congestive heart failure, and their presence is associated with symptoms, significant morbidity, and mortality. Studies have attempted to determine the prognostic significance of atrial and ventricular arrhythmias in patients with heart failure. Whether atrial fibrillation is an independent risk factor of mortality remains controversial. The presence of ventricular arrhythmias in patients with ischemic cardiomyopathy identifies patients at high risk for sudden death. However, in patients with nonischemic cardiomyopathy there is not a strong correlation between ventricular arrhythmias and increased risk for sudden death. Multiple trials using antiarrhythmic drugs, pharmacologic therapy, and implantable cardioverter defibrillators have been performed in an attempt to improve survival in patients 1) post-myocardial 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. The purpose of this article is to present an overview of arrhythmias in patients with heart failure and discuss the prevalence, prognostic significance, complications, mechanisms, and trials that have formed the current therapies presently used.

Effect of risk stratification on cost-effectiveness of the implantable cardioverter defibrillator

BACKGROUND

Implantable cardioverter defibrillators (ICDs) effectively prevent sudden cardiac death, but selection of appropriate patients for implantation is complex. We evaluated whether risk stratification based on risk of sudden cardiac death alone was sufficient to predict the effectiveness and cost-effectiveness of the ICD.

METHODS

We developed a Markov model to evaluate the cost-effectiveness of ICD implantation compared with empiric amiodarone treatment. The model incorporated mortality rates from sudden and nonsudden cardiac death, noncardiac death and costs for each treatment strategy. We based our model inputs on data from randomized clinical trials, registries, and meta-analyses. We assumed that the ICD reduced total mortality rates by 25%, relative to use of amiodarone.

RESULTS

The relationship between cost-effectiveness of the ICD and the total annual cardiac mortality rate is U-shaped; cost-effectiveness becomes unfavorable at both low and high total cardiac mortality rates. If the annual total cardiac mortality rate is 12%, the cost-effectiveness of the ICD varies from $36,000 per quality-adjusted life-year (QALY) gained when the ratio of sudden cardiac death to nonsudden cardiac death is 4 to $116,000 per QALY gained when the ratio is 0.25.

CONCLUSIONS

The cost-effectiveness of ICD use relative to amiodarone depends on total cardiac mortality rates as well as the ratio of sudden to nonsudden cardiac death. Studies of candidate diagnostic tests for risk stratification should distinguish patients who die suddenly from those who die nonsuddenly, not just patients who die suddenly from those who live.

Implantable cardioverter-defibrillators in arrhythmias: a rapid and systematic review of effectiveness

OBJECTIVE

To review the effectiveness of implantable cardioverter-defibrillators (ICDs) in the management of risk factors for sudden cardiac death.

DESIGN

Systematic review of randomised controlled trials identified from searching eight electronic databases, bibliographies of relevant studies, and consulting experts.

MAIN OUTCOME MEASURES

Absolute and relative reduction in mortality.

RESULTS

Seven trials met the inclusion criteria. These showed changes in absolute risk of total mortality ranging from +1.7% to -22.8% (relative risk reductions -7% to +54%). Estimated benefits from ICD treatment compared with conventional drug treatment at three years were 0.23 to 0.80 additional years of life.

CONCLUSIONS

Evidence suggests that ICDs reduce total mortality in particular subgroups of patients at high risk of ventricular arrhythmias. The optimal strategy for identifying the patients who could benefit most is not clearly established. Ongoing trials into the treatment of cardiac failure with ICDs may provide further evidence about subgroups in whom ICDs are most cost effective.

Advances in implantable cardioverter defibrillators

Implantable cardioverter defibrillators (ICDs) have become an important therapeutic modality for patients who have had a cardiac arrest or are at risk for life-threatening ventricular arrhythmias. Clinical trials have confirmed the role of the ICD for patients with sustained ventricular arrhythmias and have expanded the indications to include patients with coronary artery disease, left ventricular dysfunction, nonsustained ventricular tachycardia, and inducible ventricular tachycardia. Numerous technologic advances in ICDs have resulted in decreased size, greater ease of placement, and increased functionality. Important advancements have been made in the effectiveness of arrhythmia classification and electrogram storage. Dual-chamber ICDs have become increasingly sophisticated with rate-adaptive sensors. Biventricular pacing is being combined with ICD function in patients with heart failure, systolic dysfunction, and QRS widening. Future advances in devices will likely lead to improved arrhythmia classification, more advanced automated features, and additional features including more sophisticated sensors and biventricular pacing systems.

Publishing web-based guidelines using interactive decision models

Commonly used methods for guideline development and dissemination do not enable developers to tailor guidelines systematically to specific patient populations and update guidelines easily. We developed a web-based system, ALCHEMIST, that uses decision models and automatically creates evidence-based guidelines that can be disseminated, tailored and updated over the web. Our objective was to demonstrate the use of this system with clinical scenarios that provide challenges for guideline development. We used the ALCHEMIST system to develop guidelines for three clinical scenarios: (1) Chlamydia screening for adolescent women, (2) antiarrhythmic therapy for the prevention of sudden cardiac death; and (3) genetic testing for the BRCA breast-cancer mutation. ALCHEMIST uses information extracted directly from the decision model, combined with the additional information from the author of the decision model, to generate global guidelines. ALCHEMIST generated electronic web-based guidelines for each of the three scenarios. Using ALCHEMIST, we demonstrate that tailoring a guideline for a population at high-risk for Chlamydia changes the recommended policy for control of Chlamydia from contact tracing of reported cases to a population-based screening programme. We used ALCHEMIST to incorporate new evidence about the effectiveness of implantable cardioverter defibrillators (ICD) and demonstrate that the cost-effectiveness of use of ICDs improves from $74 400 per quality-adjusted life year (QALY) gained to $34 500 per QALY gained. Finally, we demonstrate how a clinician could use ALCHEMIST to incorporate a woman's utilities for relevant health states and thereby develop patient-specific recommendations for BRCA testing; the patient-specific recommendation improved quality-adjusted life expectancy by 37 days. The ALCHEMIST system enables guideline developers to publish both a guideline and an interactive decision model on the web. This web-based tool enables guideline developers to tailor guidelines systematically, to update guidelines easily, and to make the underlying evidence and analysis transparent for users.

Multicenter prospective nonrandomized study of long-term antiarrhythmic drug therapy in patients with tachyarrhythmias: Japanese Antiarrhythmics Long-Term Study-2 (JALT-2 Study)

Based on the results of the Cardiac Arrhythmia Suppression Trial (CAST), strategies for the treatment of tachyarrhythmias have changed rapidly. The Japanese Antiarrhythmics Long-Term (JALT) study was planned to investigate the present methods for choosing antiarrhythmic drugs, and the effects on long-term prognosis in patients with tachyarrhythmias in Japan. Following a 6-month preliminary study (JALT-1), there was a multicenter nonrandomized prospective study (JALT-2), with a 2-year follow-up, of patients with paroxysmal atrial fibrillation (PAF), sustained ventricular tachycardia (SVT) and nonsustained VT (NSVT). Four hundred fifty-five patients were registered, and 361 of them (79%) were analyzed. Cerebral infarction occurred in 10 of 193 patients (5.2%) with PAF. Transition to chronic AF was observed in 21 patients (10.9%), but in none of the patients receiving Ca antagonist therapy. Twenty-five patients died: 5 deaths were arrhythmic, 10 were because of pump failure, and 9 were noncardiac. The most significant difference in drug selection between JALT-1 and JALT-2 was the increase in the use of slow kinetic Na channel blockers for PAF and the decrease in the use of the same agents for VT in the JALT-2 study. A marked change of therapeutic strategy occurred in JALT-2 compared with JALT-1. Most patients with a poor prognosis had underlying heart diseases and heart failure, but the per annum rate of death by arrhythmia and pump failure in JALT-2 was less than that in JALT-1.

Implantable Cardioverter Defibrillator: Current Progress and Management

With greater technologic advances during the past decade, use of the implantable cardioverter defibrillator (ICD) has increased to more than 200,000 implants worldwide to date. Indications for ICD implant have expanded to include both patients who have survived sudden cardiac death (secondary prevention of cardiac arrest) and those who are at high risk for experiencing lethal arrhythmias (primary prevention of cardiac ar rest). Thus, it is likely that physicians will encounter defibrillators in their clinical practice and must be familiar with their indications for implant, basic opera tion, and long-term management of devices. Several prospective clinical trials have recently shown the long- term efficacy of ICD therapy at aborting sudden death in the high-risk patient population. Although still evolving, general guidelines and indications for ICD implant have been put forth and are discussed in this review. From the first defibrillation in humans during surgery in 1947 to the sophisticated dual-chamber pacing and memory functions of the modern device, ICD development has led to ever smaller devices with more complex technol ogy. The implant procedure of current ICDs parallels that used to place pacemakers. However, the anesthe sia team plays a vital role in initial ICD implantation by monitoring cardiopulmonary status during defibrilla tion threshold (DFT) testing. Additionally, long-term management of ICDs often requires repeat DFT testing with anesthesia involvement. Finally, possible electro magnetic (environmental) interactions with the ICD of which physicians should be aware are described in this article.

Implantable dual-chamber cardioverter-defibrillator-pacemaker

The fifth generation of implantable cardioverter-defibrillators offer enhanced modes of detection of atrial and ventricular arrhythmias, antitachycardia pacing and shocks, multiprogrammability, intracardiac electrogram storage, and all functions of antibradycardia dual-chamber pacing including rate responsiveness and mode switching. There is no consensus on the indications for dual-chamber pacemaker defibrillator systems. This review focuses on the four major options of newer devices that might benefit patients: 1) permanent dual-chamber pacing in ischemic coronary disease patients, 2) detection and management of atrial fibrillation or other atrial tachyarrhythmias, 3) some newer indications for pacing, and 4) the suppression of inappropriate interventions. On the basis of published data, newer indications for the dual-chamber systems, advantages and limitations, and future perspectives are discussed.

Sudden cardiac death in heart failure

Chronic heart failure (HF) and sudden cardiac death (SCD) present two major public health problems. The risk of death ranges from 10% to 50% annually in patients with HF, depending on the severity of disease. Approximately 50% of these deaths are sudden and presumed to be caused by dysrhythmias. This article defines the population at risk for SCD, explains the methods used for risk stratification, reviews current research on the pathophysiology of ventricular dysrhythmias in HF, and discusses pertinent clinical trials of therapeutic interventions on SCD in HF. The article also explores the effect of SCD on the patient and family with respect to counseling and education, resuscitative issues, and advanced directives.

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.

Drug therapy of sustained ventricular tachyarrhythmias. Is there still a role?

This article provides a review of the risks faced by patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) in the absence of a reversible or transient cause so that the goals of therapy can be clearly defined. The therapeutic approaches that have been proposed to achieve these goals are outlined and evidence comparing these various approaches to therapy is then summarized in order to propose an algorithm for the optimal use of antiarrhythmic drug therapies as primary therapy for selected VT/VF patients. Options for the ancillary uses of antiarrhythmic drug therapies in ICD patients are considered.

Identification of patients most likely to benefit from implantable cardioverter-defibrillator therapy: the Canadian Implantable Defibrillator Study

BACKGROUND

Patients with resuscitated ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation) benefit from implantable cardioverter-defibrillators (ICDs) compared with medical therapy. We hypothesized that the patients who benefit most from an ICD are those at greatest risk of death.

METHODS AND RESULTS

In the Canadian Implantable Defibrillator Study (CIDS), 659 patients with resuscitated ventricular tachyarrhythmias were randomly assigned to receive an ICD or amiodarone and were then followed for a mean of 3 years. There were 98 and 83 deaths in the amiodarone and ICD groups, respectively. We used multivariate Cox analysis to assess the impact of baseline parameters on the mortality in the amiodarone group. Reduced left ventricular ejection fraction, advanced age, and poor NYHA status identified high-risk patients (P=0.0001 to 0.0009). Quartiles of risk were constructed, and the mortality reduction associated with ICD treatment in each quartile was assessed. There was a significant interaction between risk quartile and the ICD treatment effect (P=0.011). In the highest risk quartile, there was a 50% relative risk reduction (95% CI 21% to 68%) of death in the ICD group, whereas in the 3 lower quartiles, there was no benefit. Patients who are most likely to benefit from an ICD can be identified with a simple risk score (>/=2 of the following factors: age >/=70 years, left ventricular ejection fraction </=35%, and NYHA class III or IV). Thirteen of 15 deaths that were prevented by the ICD occurred in patients with >/=2 risk factors.

CONCLUSIONS

In CIDS, patients at highest risk of death benefited most from ICD therapy. These can be identified easily on the basis of age, poor ventricular function, and poor functional status.

Arrhythmias in heart failure: current concepts of mechanisms and therapy

About one half of deaths in patients with heart failure are sudden, mostly due to ventricular tachycardia (VT) degenerating to ventricular fibrillation or immediate ventricular fibrillation. In severe heart failure, sudden cardiac death also may occur due to bradyarrhythmias. Other dysrhythmias complicating heart failure include atrial and ventricular extrasystoles, atrial fibrillation (AF), and sustained and nonsustained ventricular tachyarrhythmias. The exact mechanism of the increased vulnerability to arrhythmias is not known. Depending on the etiology of heart failure, different preconditions, including ischemia or structural alterations such as fibrosis or myocardial scarring, may be prominent. Reentrant mechanisms around scar tissue, afterdepolarizations, and triggered activity due to changes in calcium metabolism significantly contribute to arrhythmogenesis. Furthermore, alterations in potassium currents leading to action potential prolongation and an increase in dispersion of repolarization play a significant role. Treatment of arrhythmias is necessary either because patients are symptomatic or to reduce the risk for sudden cardiac death. The individual history, left ventricular function, electrophysiologic testing, and the signal-averaged ECG give useful information for identifying patients at risk for sudden cardiac death. The implantable cardioverter defibrillator (ICD) has evolved as a promising therapy for life-threatening arrhythmias. A potential role may exist for antiarrhythmic drugs, mainly amiodarone. There is growing evidence that patients with sustained VT or a history of resuscitation have the best outcome with ICD therapy regardless of the degree of heart failure. Many of these patients require additional antiarrhythmic therapy because of AF or nonsustained VTs that may activate the device. Catheter ablation or map-guided endocardial resection are additional options in selected patients but seldom represent the only therapeutic strategy.

The importance of considering trial design when interpreting clinical trial results

BACKGROUND

In recent decades, clinical trials have played an increasingly important role in determining how we practice. Trial results proving that a clinical finding poses risk have led to interventions that try to reduce risk. Clinical trials proving that a particular therapy provides better outcome than another therapy have changed the therapies we now use. Unfortunately, the results of clinical trials are too often affected by biases or design issues that may overtly or covertly alter the results or the way they should really be used. In addition, these biases and design and analysis issues are rarely evident in the abstract sections or key figures and tables in the publications reporting the trials, which may be all the busy physician either reads or remembers.

METHODS AND MATERIALS

This manuscript discusses the issues involved in optimally understanding clinical trial design and interpretation so that practitioners can better understand how to intelligently read and apply trial results to clinical practice.

CONCLUSIONS

Clinical trial results can not be properly applied without consideration of trial design features and intertrial comparisons.

Amiodarone: clinical trials

Amiodarone is an antiarrhythmic agent commonly used in the treatment of supraventricular and ventricular tachyarrhythmias. This article reviews the results and clinical implications of primary and secondary prevention trials in which amiodarone was used in one of the treatment arms. Key post-myocardial infarction primary prevention trials include the European Myocardial Infarct Amiodarone Trial (EMIAT) and the Canadian Amiodarone Myocardial Infarction Trial (CAMIAT), both of which demonstrated that amiodarone reduced arrhythmic but not overall mortality. In congestive heart failure patients, amiodarone was studied as a primary prevention strategy in two pivotal trials: Grupo de Estudio de la Sobrevida en la Insuficiencia Cardiac en Argentina (GESICA) and Amiodarone in Patients With Congestive Heart Failure and Asymptomatic Ventricular Arrhythmia (CHF-STAT). Amiodarone was associated with a neutral overall survival and a trend toward improved survival in nonischemic cardiomyopathy patients in CHF/STAT and improved survival in GESICA. In post-myocardial infarction patients with nonsustained ventricular tachycardia and a depressed ejection fraction, the Multicenter Automatic Defibrillator Implantation Trial (MADIT) demonstrated that implantable cardioverter-defibrillators (ICD) statistically improved survival compared to the antiarrhythmic drug arm, most of whose patients were taking amiodarone. In patients with histories of sustained ventricular tachycardia or ventricular fibrillation, the Cardiac Arrest Study in Seattle: Conventional Versus Amiodarone Drug Evaluation (CASCADE) trial demonstrated that empiric amiodarone lowered arrhythmic recurrence rates compared to other drugs guided by serial Holter or electrophysiologic studies. However, arrhythmic death rates were high in both treatment arms of the study. Several secondary prevention trials, including the Antiarrhythmics Versus Implantable Defibrillators Study (AVID), the Canadian Implantable Defibrillator Study (CIDS), and the Cardiac Arrest Study Hamburg (CASH), have demonstrated the superiority of ICD therapy compared to empiric amiodarone in improving overall survival. Based on the above findings, amiodarone is safe to use in post-myocardial infarction and congestive heart failure patients that need antiarrhythmic therapy. Although amiodarone is effective in treating malignant arrhythmias, high-risk patients should be considered for an ICD as frontline therapy.

Implantable defibrillators and antiarrhythmic drugs in patients at risk for lethal arrhythmias

The high mortality rate and frequency of ventricular arrhythmias in patients with congestive heart failure has prompted numerous clinical trials aimed at reducing mortality by addressing arrhythmic death. Recently completed trials have suggested that for patients who have survived cardiac arrest, the preferred treatment may be an implantable cardioverter defibrillator (ICD). From the standpoint of primary prevention, implantable defibrillators and amiodarone have received the most attention. It remains unclear, however, to which patients these studies apply, and if and how the results might be generalized. No available studies confirm an additional benefit of pharmacologic or device-based antiarrhythmic therapy beyond that offered by optimal treatment with beta blockers, angiotensin-converting enzyme inhibitors, and lipid-lowering drugs in the majority of patients with cardiomyopathy. Clinical trials are ongoing to address these issues.

Evaluation of antiarrhythmic drug efficacy in patients with an ICD: unlimited potential or replete with complexity and problems?

There are a number of novel ways in which implantable cardioverter defibrillator (ICD) endpoints can be used in clinical trials to evaluate antiarrhythmic drugs. The advances in ICD technology (storage, retrieval, and accurate interpretation of ICD electrograms) expand the potential to include the use of an ICD endpoint as a clinical surrogate for sudden death. The ICD also provides the necessary safety net to test new drugs. The frequent need for antiarrhythmic drugs in patients already fitted with an ICD (e.g., for atrial fibrillation) necessitates knowledge of the drugs' effect on defibrillator threshold. There are interpretative problems and challenges associated with all types of ICD trials. A particular difficult issue is the degree to which the results of data on antiarrhythmic drug efficacy and safety acquired in the context of an ICD endpoint trial might be extrapolated to patient populations in which the device is not used. These and other challenging issues are discussed, with the goal of enhancing the design and interpretation of clinical trials featuring ICD endpoints.

Is primary antiarrhythmic drug therapy for ventricular arrhythmias obsolete?

Sudden cardiac death (SCD) remains a major public health threat. Patients with aborted SCD have a high incidence of recurrent life-threatening ventricular arrhythmias. Antiarrhythmic drug approaches dominated early attempts to prevent SCD; however, several trials with sotalol and amiodarone revealed an unacceptably high rate of recurrent arrhythmic events. With the advent of the implantable cardioverter defibrillator (ICD), the primary role of antiarrhythmic drug therapy for the secondary prevention of SCD has been called into question. Two recently completed trials, the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial and the Canadian Implantable Defibrillator Study (CIDS), confirm the superiority of the ICD over the best medical therapy for saving lives.

Interactions of antiarrhythmic drugs with implantable defibrillator therapy for atrial and ventricular tachyarrhythmias

Implantable cardioverter defibrillators (ICDs) have proven highly successful in the treatment of recurrent ventricular and atrial arrhythmias. Despite their high efficacy in terminating arrhythmias, concomitant therapy with antiarrhythmic drugs in ICD recipients remains common. Antiarrhythmic drugs are employed in an attempt to to limit patient exposure to high-energy shocks, primarily by reducing the number of arrhythmia reccurrences, suppressing coexisting arrhythmias, affecting rate and organization of tachycardias, and increasing efficacy of painless pacing therapies. Data regarding interaction of antiarrhythmic drugs with ICDs are incomplete and mostly based on animal models; however, it is clear that antiarrhythmic drugs affect all aspects of function of devices such as defibrillation threshold, pacing threshold, and sensing of both atrial and and ventricular arrhythmias. Because significant change in any of these functions may result in a nonfunctional device, and magnitude of drug effect in an individual patient is unpredictable, careful assessment of ICD function after an institution of therapy with antiarrhythmic drugs is mandatory.

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.

Design and results of the antiarrhythmics vs implantable defibrillators (AVID) registry. The AVID Investigators

BACKGROUND

The Antiarrhythmics Versus Implantable Defibrillators (AVID) Study compared treatment with implantable cardioverter-defibrillators versus antiarrhythmic drugs in patients with life-threatening ventricular arrhythmias (VAs). AVID maintained a Registry on all patients, randomized or not, with any VA or unexplained syncope who could be considered for either of the treatment strategies. Trial-eligible arrhythmias were the categories of VF cardiac arrest, Syncopal VT, and Symptomatic VT, below.

METHODS AND RESULTS

Of 5989 patients screened, 4595 were registered and 1016 were randomized. Mortality follow-up through 1996 was obtained on the 4219 Registry patients enrolled before 1997 through the National Death Index. Crude mortality rates (mean+/-SD, follow-up, 16.9+/-11.5 months) were: VF cardiac arrest, 17.0% (n=1399, 238 deaths); Syncopal VT, 21.2% (n=598, 127 deaths); Symptomatic VT, 15.8% (n=1065, 168 deaths); Stable (asymptomatic) VT, 19.7% (n=497, 98 deaths); VT/VF with transient/correctable cause, 17.8% (n=270, 48 deaths); and Unexplained syncope, 12.3% (n=390, 48 deaths).

CONCLUSIONS

Patients with seemingly lower-risk or unknown-risk VAs (asymptomatic VT, and VT/VF associated with a transient factor) have a (high) mortality similar to that of higher-risk, AVID-eligible VAs. The similar (and poor) prognosis of most patients with VT/VF suggests the need for reevaluation of a priori risk grouping and raises the question of the appropriate arrhythmia therapy for a broad range of patients.

Distributed decision support using a web-based interface: prevention of sudden cardiac death

Although decision models can provide a formal foundation for guideline development and clinical decision support, their widespread use is often limited by the lack of platform-independent software that geographically dispersed users can access and use easily without extensive training. To address these limitations the authors developed a World Wide Web-based interface for previously developed decision models. They describe the use and functionality of the interface using a decision model that evaluates the cost-effectiveness of strategies for preventing sudden cardiac death. The system allows an analyst to use a web browser to interact with the decision model and to change the values of input variables within pre-specified ranges, to specify sensitivity or threshold analyses, to evaluate the decision model, and to view the results generated dynamically. The web site also provides linkages to an explanation of the model, and evidence tables for input variables. The system demonstrates a method for providing distributed decision support to remote users such as guideline developers, decision analysts, and potentially practicing physicians. The web interface provides platform-independent and almost universal access to a decision model. This approach can make distributed decision support both practical and economical, and has the potential to increase the usefulness of decision models by enabling a broader audience to incorporate systematic analyses into both policy and clinical decisions.

Implantable cardioverter-defibrillators

Implantable defibrillators have become the dominant therapeutic modality for patients with life-threatening ventricular arrhythmias. Current defibrillators are small (<60 mL) and implanted with techniques similar to standard pacemakers. They provide high-energy shocks for ventricular fibrillation and rapid ventricular tachycardia, antitachycardia pacing for monomorphic ventricular tachycardia, as well as antibradycardia pacing. Newer devices incorporating an atrial lead allow dual-chamber pacing and better discrimination between ventricular and supraventricular tachyarrhythmias. Randomized controlled trials have shown superior survival with implantable defibrillators than with antiarrhythmic drugs in survivors of life-threatening ventricular tachyarrhythmias and in high-risk patients with coronary artery disease. Complications associated with implantable defibrillator therapy include infection, lead failure, and spurious shocks for supraventricular tachyarrhythmias. Most patients adapt well to living with an implantable defibrillator, although driving often has to be restricted. Limited evidence suggests that implantable defibrillator therapy is cost-effective when compared with other widely accepted treatments. The use of implantable defibrillators is likely to continue to expand in the future. Ongoing clinical trials will define further prophylactic indications of the implantable defibrillator and clarify its cost-effectiveness ratio in different clinical settings.

Evaluation of coronary revascularization to prevent tachycardia recurrences in survivors of ventricular fibrillation

Long-term follow-up of 29 consecutive survivors of ventricular fibrillation who underwent revascularization demonstrated that recurrent arrhythmics events were common. Because revascularization alone does not prevent arrhythmia recurrence, treatment with an implantable defibrillator should be considered in these patients.

New primary prevention trials of sudden cardiac death in patients with left ventricular dysfunction: SCD-HEFT and MADIT-II

Primary prevention of sudden arrhythmic death in patients with organic heart disease with poor left ventricular function and/or heart failure is currently a major challenge in cardiology. Amiodarone (with or without beta blockers) and the implantable cardioverter defibrillator (ICD) are considered the 2 major therapeutic tools to prevent sudden arrhythmic death in these patients. Two large trials have been launched to define the prophylactic benefit of the ICD or amiodarone on total mortality in patients that receive optimal heart failure and anti-ischemic treatment but remain at high risk of dying suddenly. The Sudden Cardiac Death in Heart Failure Trial (SCD-Heft) is designed to determine whether amiodarone or the ICD will decrease overall mortality in patients with coronary artery disease or nonischemic cardiomyopathy who are in heart failure New York Heart Association (NYHA) class II or III and have a left ventricular ejection fraction < 35%. The primary endpoint is total mortality; secondary objectives are comparison of arrhythmic and nonarrhythmic mortality and morbidity in the 3 arms as well as quality of life, cost-effectiveness, and incidence of episodes of ventricular tachyarrhythmias. The Multicenter Automatic Defibrillator Implantation Trial (MADIT) II is a follow-up study to the MADIT trial. It examines the prophylactic benefit in coronary artery disease patients with a left ventricular ejection fraction of < 30%, who have had at least 1 myocardial infarction but require no further risk stratification. MADIT II is a sequential design trial that compares ICD versus no ICD therapy. Programmed electrical stimulation to test inducibility of ventricular tachycardia is performed during ICD implantation, and various noninvasive risk markers are tested after randomization. Primary endpoint is total mortality, and secondary objectives are quality-of-life issues as well as cost-effectiveness ratio.

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.

Potential benefit of biventricular pacing in patients with congestive heart failure and ventricular tachyarrhythmia

Treatment of congestive heart failure (CHF) aims for symptomatic relief and reduction of mortality both from sudden death and pump failure. The implantable cardioverter defibrillator (ICD) is highly effective in the prevention of sudden death, but no mortality benefit in advanced CHF has yet been shown. Biventricular pacing may lead to functional improvement in selected patients with CHF. Thus, a biventricular pacemaker with defibrillation capabilities may be ideal for patients with advanced CHF. We retrospectively analyzed the data from 384 patients (age 59 +/- 12 years, 322 male and 62 female) with regard to New York Heart Association (NYHA) CHF class, mean QRS duration, mean PR interval, presence of a QRS > 120 msec and incidence of atrial fibrillation at the time of ICD implantation. Based on eligibility criteria from studies in biventricular pacing, we analyzed how many patients may benefit from biventricular pacing. Patients with CHF were older (NYHA class III: 60.9 +/- 9.7, class II: 61.3 +/- 10 versus class I: 50.8 +/- 13.6 years, p < 0.001 each) and mean QRS duration was longer with advanced CHF (NYHA class III 127.8 +/- 30 msec; class II 119.4 +/- 27.7 msec; class 0-1: 103.9 +/- 17.7 msec, p < 0.001, analysis of variance) as was the mean PR interval (NYHA class III 189.9 +/- 33.5 msec; class II 176.1 +/- 29.3 msec; class 0-1 162.7 +/- 45.9 msec, p < 0.001, analysis of variance). The incidence of atrial fibrillation was higher in class III (25.5%) compared with class 0-1 (16.9%) and class II patients (14.1%, p = 0.043, chi-square test). A total of 28 patients (7.3%) fulfilled eligibility criteria for biventricular pacing if NYHA class III patients were considered candidates and 48 (12.5%) if patients with NYHA II CHF and ejection fraction < or = 30% were included. Thus, biventricular pacing may offer a promising therapeutic approach for a significant proportion of patients with CHF at risk for ventricular tachyarrhythmia.