What is the optimal left ventricular ejection fraction cut-off for risk stratification for primary prevention of sudden cardiac death early after myocardial infarction?

AIMS The optimal left ventricular ejection fraction (LVEF) to select patients early post myocardial infarction (MI) for risk stratification for prevention of sudden cardiac death (SCD) in the era of primary percutaneous coronary intervention (PPCI) is unknown. METHODS AND RESULTS Consecutive patients (n = 1722) treated with PPCI for ST-elevation MI underwent early (median 4 days) LVEF assessment. An electrophysiological study (EPS) was performed if LVEF ≤40% and a prophylactic implantable-cardioverter defibrillator (ICD) implanted for a positive [inducible monomorphic ventricular tachycardia (VT)], but not a negative, result. According to an early LVEF, a primary endpoint of inducible VT at EPS and a secondary endpoint of death or arrhythmia (SCD, resuscitated cardiac arrest or ECG-documented VT/ventricular fibrillation) were determined. The proportion of patients with early LVEF >40, 36-40, 31-35, and ≤30% were 75% (n = 1286), 7% (n = 128), 8% (n = 136), and 10% (n = 172), respectively. Inducible VT occurred in 22, 25, and 40% of patients with LVEF 36-40, 31-35, and ≤30%, respectively (P = 0.014). Three-year death or arrhythmia occurred in 6.6 ± 0.8, 8.1 ± 2.6, 18.0 ± 3.4, and 37.4 ± 3.9% of patients with LVEF >40, 36-40, 31-35, and ≤30%, respectively (overall P<0.001; LVEF 36-40% vs. LVEF > 40% P = 0.265). The number of EPS-positive patients implanted with an ICD to treat one or more arrhythmic event (95% confidence interval) was 18.3 ± 2.4, 11.5 ± 3.0, and 4.2 ± 5.6 if LVEF is 36-40, 31-35, and ≤30%, respectively. CONCLUSION A cut-off LVEF of ≤40% selects patients with a high incidence of inducible VT post-PPCI. Patients with LVEF ≤35% and inducible VT appear to derive a greater benefit from prophylactic ICD implantation due to their higher risk of death or arrhythmia.