Long-Term Benefit of Primary Prevention With an Implantable Cardioverter-Defibrillator An Extended 8-Year Follow-Up Study of the Multicenter Automatic Defibrillator Implantation Trial II

Background-The Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II) showed a significant 31% reduction in the risk of death with primary implantable cardioverter-defibrillator (ICD) therapy during a median follow-up of 1.5 years. However, currently there are no data on the long-term efficacy of primary defibrillator therapy. Methods and Results-MADIT-II enrolled 1232 patients with ischemic left ventricular dysfunction who were randomized to ICD and non-ICD medical therapy and were followed up through November 2001. For the present long-term study, we acquired posttrial mortality data through March 2009 for all study participants (median follow-up, 7.6 years). Multivariate Cox proportional hazards regression modeling was performed to calculate the hazard ratio for ICD versus non-ICD therapy during long-term follow-up. At 8 years of follow-up, the cumulative probability of all-cause mortality was 49% among patients treated with an ICD compared with 62% among non-ICD patients (P<0.001). Multivariate analysis demonstrated that ICD therapy was associated with a significant long-term survival benefit (hazard ratio for 0- through 8-year mortality=0.66 [95% confidence interval, 0.56 to 0.78]; P<0.001). Treatment with an ICD was shown to be associated with a significant reduction in the risk of death during the early phase of the extended follow-up period (0 through 4 years: hazard ratio=0.61 [95% confidence interval, 0.50 to 0.76]; P<0.001) and with continued life-saving benefit during the late phase of follow-up (5 through 8 years: hazard ratio=0.74 [95% confidence interval, 0.57 to 0.96]; P=0.02). Conclusions-Our findings demonstrate a sustained 8-year survival benefit with primary ICD therapy in the MADIT-II population. (Circulation. 2010; 122:1265-1271.)