Reduced Ejection Fraction After Myocardial Infarction: Is it Sufficient to Justify Implantation of a Defibrillator?

Abstract

Improved survival after prophylactic implantation of a defibrillator in patients with reduced left ventricular ejection fraction (EF) after myocardial infarction (MI) has been demonstrated in patients with remote MI experienced in the 1990's. The absolute survival benefit conferred by this recommended strategy must be related to the current risk of arrhythmic death which is evolving. This study evaluates the mortality rate in survivors of MI with impaired left ventricular function and its relation to pre-discharge baseline characteristics. Clinical records of patients who had sustained acute MI from 1999 to 2000 and were discharged with an EF ≤ 0.40 were included. Baseline characteristics, drug prescriptions and invasive procedures were recorded. Bivariate and multivariate analyses were performed using a primary endpoint of total mortality. 165 patients were included. During a median follow-up of 30 months (interquartile range 22-36) 18 patients died. One and two-year mortality rates were 6.7% and 8.6%, respectively. Variables reflecting coronary artery disease and its management (prior MI, acute reperfusion, complete revascularization) had a greater impact on mortality than variables reflecting mechanical dysfunction (EF, Killip class). Mortality in survivors of MI with reduced EF is substantially lower than reported in the 1990's. This decreased absolute mortality implies a proportional increase in the number of patients needed to treat with a prophylactic defibrillator. The risk of event may even be sufficiently low to limit the detectable benefit of defibrillators in patients with the prognostic features identified in our study. This argues for additional risk stratification prior to the prophylactic implantation of a defibrillator.