Mechanisms of Sudden Cardiac Death in Myocardial Infarction Survivors

Sudden death is a catastrophic but unpredictable complication of coronary artery disease and is frequently the consequence of an acute ischemic event.1–3 The efficacy of the implantable cardioverter-defibrillator (ICD) in reducing sudden cardiac death incidence is irrefutable and strongly supported by evidence from randomized trials of both primary and secondary prevention (Figure 1).4–8 Nonetheless, the 2 neutral trials9,10 raise intriguing and puzzling issues in regard to the temporal relationship between myocardial infarction (MI), coronary revascularization, residual myocardial ischemia, and severe left ventricular dysfunction and its impact on the mechanisms of presumed sudden cardiac death and the efficacy of the ICD. In this respect, this commentary addresses current knowledge regarding the mechanisms of death early and late after MI, limitations in our abilities to stratify risk, and analyses from the randomized trials in an attempt to reconcile the apparently paradoxical observation that the highest rate of sudden cardiac death occurs the first few weeks after MI and that the only ICD trial to address this population was neutral.10 Figure 1. The efficacy of ICD for the primary prevention of death. Data were derived from the study by Solomon et al26 and from the randomized ICD trials for both primary and secondary prevention of sudden cardiac death.4–8The causes of death after MI are multifactorial and depend in part on the duration of time that has elapsed since the initial MI. During the acute phase of the MI, sudden death is typically the result of ischemia that provokes lethal ventricular arrhythmias.11,12 Mechanical complications resulting in profound hemodynamic derangements such as ventricular or papillary muscle rupture, pericardial tamponade, septal defects, and ischemic valvular dysfunction also may mimic sudden arrhythmic death, even if the rhythm is not ventricular fibrillation. A similar sequence of events may occur …