Clinical phenotypes and outcomes associated with improved left ventricular ejection fraction after biventricular pacing

Background: In some patients who receive a cardiac resynchronization therapy (CRT) device, the left ventricular ejection fraction (LVEF) does not improve. Methods: We analyzed patients enrolled in the REVERSE, MADIT-CRT, and BLOCK-HF trials, restricting the analysis to those who received CRT. Characteristics of patients with or without improved LVEF were compared using two sample t-tests and Pearson’s chi-square tests. Kaplan–Meier survival curves were constructed to display time-to-event data. A log-rank test was used to compare event rates for patients with or without improved LVEF. Mixed effects Cox Proportional-Hazards models adjusting for covariates were used to analyze time to death or heart failure hospitalization (HFH) and time to death. Results: Of 1065 included patients, 75% (802) were men, 87% (793) were White, 11% (118) were Black, and 7% (72) were Hispanic. LVEF improved in 910 (85%) patients and did not in 155 (15%). Patients with an improved LVEF were less likely to have ischemic cardiomyopathy (ICM) (54% vs 76%; p = 0.004), more likely to have LBBB (73% vs 53%; p = < 0.001), and had longer QRS duration (159 vs 150 ms; p = < 0.001). In adjusted analyses, improved LVEF was associated with a longer time to HFH or death (HR 0.40; 95% CI 0.26–0.62; p < 0.001) or death alone (HR 0.27; 95% CI 0.15–0.48; p < 0.001). Conclusions: Patients with improvement in LVEF post-CRT implantation are less likely to have ICM and more likely to have LBBB and a longer QRS interval. Improvement in LVEF was associated with better outcomes.