Adding Defibrillation Therapy to Cardiac Resynchronization on the Basis of the Myocardial Substrate.

<bold>Background: </bold>Patients with nonischemic dilated cardiomyopathy (DCM) may be at lower risk for ventricular arrhythmias compared with those with ischemic cardiomyopathy (ICM). In addition, DCM has been identified as a predictor of positive response to cardiac resynchronization therapy (CRT).<bold>Objectives: </bold>The aim of this study was to investigate the impact of an additional implantable cardioverter-defibrillator over CRT, according to underlying heart disease, in a large study group of primary prevention patients with heart failure.<bold>Methods: </bold>This was an observational, multicenter, European cohort study of 5,307 consecutive patients with DCM or ICM, no history of sustained ventricular arrhythmias, who underwent CRT implantation with (n = 4,037) or without (n = 1,270) a defibrillator. Propensity-score and cause-of-death analyses were used to compare outcomes.<bold>Results: </bold>After a mean follow-up period of 41.4 ± 29.0 months, patients with ICM had better survival when receiving CRT with a defibrillator compared with those who received CRT without a defibrillator (hazard ratio for mortality adjusted on propensity score and all mortality predictors: 0.76; 95% confidence interval [CI]: 0.62 to 0.92; p = 0.005), whereas in patients with DCM, no such difference was observed (hazard ratio: 0.92; 95% CI: 0.73 to 1.16; p = 0.49). Compared with recipients of defibrillators, the excess mortality in patients who did not receive defibrillators was related to sudden cardiac death in 8.0% among those with ICM but in only 0.4% of those with DCM.<bold>Conclusions: </bold>Among patients with heart failure with indications for CRT, those with DCM may not benefit from additional primary prevention implantable cardioverter-defibrillator therapy, as opposed to those with ICM. [ABSTRACT FROM AUTHOR]