Clinical Question: Do implantable cardioverter defibrillators improve outcomes in at-risk patients after myocardial infarction (MI)?

Setting: Inpatient (any location) with outpatient follow-up

Study Design: Randomized controlled trial (single-blinded)

Allocation: Concealed

Synopsis: Implantable cardioverter defibrillators can reduce mortality rates in selected patients. In this industry-sponsored study, adults with a recent MI, a left ventricular ejection fraction less than or equal to 0.35, and relative tachycardia (i.e., more than 80 beats per minute) or decreased heart rate variability were randomized to treatment with implantable cardioverter defibrillators or usual care. This was an open-label trial with no attempt at sham surgery or implantation of sham implantable cardioverter defibrillators. The primary outcomes of all-cause mortality or death caused by cardiac arrhythmia were assessed blindly and analysis was by intention to treat.

The groups were balanced at the beginning of the study, with 332 patients in the implantable cardioverter defibrillator group and 342 patients in the control group. Patients were followed for a mean of 30 months, with a maximum follow-up of 48 months. Patients in the implantable cardioverter defibrillator group experienced significantly fewer arrhythmic deaths (1.5 versus 3.5 percent; number needed to treat = 50; 95 percent confidence interval [CI], 27 to 209). Unfortunately, they also experienced more nonarrhythmic deaths (6.1 versus 3.5 percent; number needed to treat to harm = 38; 95 percent CI, 20 to 150).

There was no significant difference between groups regarding the most important patient-oriented outcome: all-cause mortality (7.5 percent for the implantable cardioverter defibrillator group versus 6.9 percent for the control group). The difference in non-arrhythmic deaths was caused largely by more cardiac nonarrhythmic deaths. The authors speculate that a group of patients with severe heart disease are “saved” from an arrhythmic death only to die from pump failure without any clinically important increase in the overall lifespan. Implantable defibrillators have been shown to be effective in patients with nonischemic cardiomyopathy (Desai AS, et al. Implantable defibrillators for the prevention of mortality in patients with nonischemic cardiomyopathy: a meta-analysis of randomized controlled trials. JAMA December 15, 2004;292:2874-9).

Bottom Line: Implantable cardioverter defibrillators do not reduce mortality in patients with MI who are at high risk for ventricular arrhythmia. (Level of Evidence: 1b)