Primary Prevention of Sudden Cardiac Death Early Post-Myocardial Infarction: Root Cause Analysis for Implantable Cardioverter-Defibrillator Failure and Currently Available Options.

Abstract

The rate of death, including sudden cardiac death (SCD), is highest during the early period after a myocardial infarction (MI).1 Implantable cardioverter–defibrillators (ICDs) improve survival rates of patients with various heart conditions who are at high risk of ventricular tachyarrhythmia (VTA), by terminating those VTA.2–5 However, ICDs in conjunction with optimal medical therapy have failed to improve survival when implanted for primary prevention early after an MI in 2 prospective randomized controlled trials when compared with optimal medical therapy alone: the DINAMIT (Defibrillator in Acute Myocardial Infarction Trial)6 and the IRIS (Immediate Risk Stratification Improves Survival Trial).7 Therefore, current guidelines8 indicate that patients should not receive an ICD within 40 days after an MI without revascularization (DINAMIT criteria) or within 3 months after an MI with revascularization which leaves patients at risk for SCD during this gap of vulnerability period.9 Different hypotheses that may underlie the negative results of the DINAMIT and IRIS trials will be reviewed here in detail. A meta-analysis of the outcomes of these 2 studies is performed. In addition, we estimate annualized mortality through 3 years for these 2 trials and all other major primary prevention ICD trials with ischemic cardiomyopathy, creating a basis for comparison across studies. The current options available to reduce SCD post-MI will be discussed, including the potential impact of a wearable cardioverter–defibrillator (WCD; LifeVest; Zoll, Pittsburgh, PA) as a bridging therapy, in light of the various hypotheses underlying the lack of ICD benefit in DINAMIT and IRIS patients. The incidence of SCD is increased within the first few months post-MI. It is highest within the first month after an MI (1.2%–1.4%),1–10 followed by a progressive decline until a plateau after a few months. The mechanism of SCD post-MI, adjudicated initially …