Outcomes of cardiac resynchronization therapy with or without defibrillation in patients with nonischemic cardiomyopathy

Background Recent studies have cast doubt on the benefit of cardiac resynchronization therapy (CRT) with defibrillation (CRT-D) versus pacing (CRT-P) for patients with nonischemic cardiomyopathy (NICM). Left ventricular myocardial scar portends poor clinical outcomes. Objectives The aim of this study was to determine whether CRT-D is superior to CRT-P in patients with NICM either with (+) or without (−) left ventricular midwall fibrosis (MWF), detected by cardiac magnetic resonance. Methods Clinical events were quantified in patients with NICM who were +MWF (n = 68) or −MWF (n = 184) who underwent cardiac magnetic resonance prior to CRT device implantation. Results In the total study population, +MWF emerged as an independent predictor of total mortality (adjusted hazard ratio [aHR]: 2.31; 95% confidence interval [CI]: 1.45 to 3.68), total mortality or heart failure hospitalization (aHR: 2.02; 95% CI: 1.32 to 3.09), total mortality or hospitalization for major adverse cardiac events (aHR: 2.02; 95% CI: 1.32 to 3.07), death from pump failure (aHR: 1.95; 95% CI: 1.11 to 3.41), and sudden cardiac death (aHR: 3.75; 95% CI: 1.26 to 11.2) over a maximum follow-up period of 14 years (median 3.8 years [interquartile range: 2.0 to 6.1 years] for +MWF and 4.6 years [interquartile range: 2.4 to 8.3 years] for −MWF). In separate analyses of +MWF and −MWF, total mortality (aHR: 0.23; 95% CI: 0.07 to 0.75), total mortality or heart failure hospitalization (aHR: 0.32; 95% CI: 0.12 to 0.82), and total mortality or hospitalization for major adverse cardiac events (aHR: 0.30; 95% CI: 0.12 to 0.78) were lower after CRT-D than after CRT-P in +MWF but not in −MWF. Conclusions In patients with NICM, CRT-D was superior to CRT-P in +MWF but not −MWF. These findings have implications for the choice of device therapy in patients with NICM.