ICD update: New evidence and emerging clinical roles in primary prevention of sudden cardiac death

PURPOSE: To review recent major randomized trials of implantable cardioverter-defibrillators (ICDs) and discuss the impact of their results on evolving ICD indications. EPIDEMIOLOGY: Sudden cardiac deaths (SCDs) occur about 6 to 9 × more frequently in patients with heart failure (HF) than in patients without HF, and about 550 000 new HF cases are diagnosed every year. REVIEW SUMMARY: Efficacy of ICDs in patients who have already had life-threatening ventricular arrhythmias is well established. More recent evidence that shows ICD efficacy in primary prevention (ie, patients at high risk of first cardiac arrests, such as patients with prior myocardial infarction [MI] and low left ventricular ejection fraction [LVEF]) has suddenly expanded the potential clinical role of these expensive devices. Most significantly, the Multicenter Automatic Defibrillator Implantation Trial (MADIT)-II showed a 31% reduction in mortality with ICDs in patients with prior MI, LVEF of ≤30%, and New York Heart Association (NYHA) Class I-III disease; the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) demonstrated a 23% reduction in mortality with ICDs in patients with ischemic or nonischemic cardiomyopathy, LVEF of ≤35%, and NYHA Class II or III disease; and the Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION) trial showed a 36% reduction in mortality with a device that combined ICD functions with resynchronization in patients with intraventricular conduction delays. TYPE OF AVAILABLE EVIDENCE: Unstructured review of randomized-controlled trials. GRADE OF AVAILABLE EVIDENCE: Good. CONCLUSION: ICDs reduce mortality in patients with cardiomyopathy, NYHA Class II-III disease, and LVEF of ≤35% (or Class I with LVEF of ≤30%). ICDs with resynchronization functionality reduce mortality in patients with LVEF of ≤35%, NYHA Class III-IV disease, and ventricular dyssynchrony. Although ICDs are cost effective relative to other common cardiovascular treatments, the societal costs associated with more widespread use of ICDs warrant development of evidence-based patient risk-stratification methods.