Implantable Cardioverter-Defibrillator Efficacy in Patients With Heart Failure and Left Ventricular Dysfunction (from the MADIT II Population)

The Multicenter Automatic Defibrillator Implantation Trial II demonstrated a significant 31% reduction in the risk of mortality in postinfarction patients with low ejection fraction (EF ≤30%). Recently, results from the Sudden Death in Heart Failure Trial indicated that a subgroup of patients with New York Heart Association (NYHA) class III heart failure had less benefit from an implantable cardioverter-defibrillator (ICD) than patients with less advanced heart failure. This study evaluates the association between NYHA class, EF, and blood urea nitrogen (BUN) levels as measures of heart failure and left ventricular dysfunction, and ICD benefit in reducing mortality as well as the association of these parameters with ICD therapy for ventricular tachyarrhythmias. NYHA class I was identified in 442 patients (36%), class II in 425 (35%), and class III in 350 patients (29%). EF ≤20% was present in 472 patients (38%), EF of 21% to 25% in 359 patients (29%), and EF of 26% to 30% in 401 patients (33%). BUN ≤25 mg/dl was present in 850 patients (70%) and >25 mg/dl in 368 patients (30%). Patients with higher NYHA class and BUN had higher mortality (34%) and a higher risk of arrhythmic events (33% to 35%) than patients in lower functional groups (16% to 20%). EF did not differentiate the risk. There was no evidence for significant interactions between mortality, ICD therapy, and tested parameters. In conclusion, patients with more advanced heart failure have a higher risk of mortality and arrhythmic events than patients with less severe disease. However, there is no significant difference in the benefit from ICD therapy among the above subgroups of patients in the Multicenter Automatic Defibrillator Implantation Trial.