Current Evidence Base for Use of the Implantable Cardioverter–Defibrillator

Abstract

Almost 4 decades after its conception the implantable cardioverter–defibrillator (ICD) has emerged as a widely accepted treatment modality for the prevention of sudden cardiac death (SCD). The indications for ICD therapy have rapidly expanded over the past 10 years, and, today, >100 000 ICDs are implanted annually in the United States. More recently, however, some have raised words of caution as to the potential overestimation of ICD-associated benefits and hazards in individual patients.1,2 Therefore, this review summarizes the current scientific basis for ICD indications, puts it in context with recent guidelines, and discusses areas where additional trial evidence is needed to clarify pending issues regarding the optimal use of device therapy. The term secondary prevention refers to the prevention of SCD in patients who have survived previous cardiac arrest or an episode of sustained ventricular tachycardia (VT). The term primary prevention of SCD describes patient populations known to be at high risk for cardiac arrest because of preexisting cardiovascular disease but who have not yet experienced sustained VT or ventricular fibrillation (VF).3 ### Secondary Prevention Trials The secondary prevention strategy that emerged from observations indicating a high recurrence rate of VT or VF in survivors of cardiac arrest4,5 was the first to be tested in randomized clinical trials (Table 1). There are 3 secondary prevention ICD trials, the Antiarrhythmics Versus Implantable Defibrillator (AVID) trial, the Canadian Implantable Defibrillator (CIDS) trial, and the Cardiac Arrest Study Hamburg (CASH) trial, all initiated between the late 1980s and early 1990s.6–8 The AVID trial was the first to report its results and showed a statistically significant survival benefit over antiarrhythmic drugs (mostly amiodarone), with an absolute risk reduction of 7% over 2 years.6 After publication of AVID, the CIDS trial was prematurely stopped owing to the similarities between …