Relationship of electro-mechanical remodeling to survival rates after cardiac resynchronization therapy

Cardiac resynchronization therapy, when added to optimal medical therapy, increases longevity in symptomatic congestive heart failure patients with left ventricular ejection fractions (LVEF)≤0.35 and QRS durations>120 ms. Cardiac resynchronization therapy is also associated with electrical and mechanical reverse remodeling. We examined whether reverse remodeling predicts increased survival rates in non-trial settings. Recipients of cardiac resynchronization therapy and defibrillators (n=112; 78 men; mean age, 69±11 yr) underwent repeat echocardiography and electrocardiography at least 90 days after device implantation. Forty patients had mechanical responses of at least 0.05 improvement in absolute LVEF; 56 had electrical responses (any narrowing of biventricular-paced QRS duration compared with the electrocardiogram immediately after therapy). During a mean follow-up period of 3.1±1.7 years, 55 patients died. The average death rate per 100 person-years was lower among mechanical responders than nonresponders (9.2% vs 23.9%; P=0.009); the unadjusted hazard ratio was 0.39 (95% confidence interval [CI], 0.19-0.79). In a multivariate model adjusted for age, sex, baseline LVEF, and QRS duration, mechanical responders had 60% better survival than nonresponders (hazard ratio=0.40; 95% CI, 0.21-0.79; P=0.008). No difference in survival was observed in electrical response. In our association of absolute change in LVEF over the observed range with death (using restricted cubic splines), we observed a linear relationship with survival. In patients given cardiac resynchronization therapy, mechanical but not electrical remodeling was associated with better survival rates, suggesting that mechanical remodeling underlies this therapy's mechanism of conferring a survival benefit.