Patients receiving conventional cardiac resynchronization therapy (CRT) for left bundle branch block often have near-normal right bundle conduction, meaning that right ventricular (RV) pacing could be unnecessary or detrimental. Adaptive CRT synchronizes left ventricular (LV) pacing with intrinsic RV activation during periods of normal atrioventricular conduction, while during abnormal atrioventricular conduction adaptive CRT provides dynamically optimized biventricular pacing (as is provided by conventional CRT). In the largest randomized controlled trial of CRT conducted so far — involving 3,617 patients (43.4% female) from 227 hospitals in 27 countries worldwide — Wilkoff et al. report no advantage for adaptive CRT compared with conventional CRT in terms of all-cause death or intervention for heart failure decompensation.
This trial was halted in June 2022 when no statistically significant between-group difference was found in the composite primary outcome (23.5% with adaptive CRT versus 25.7% with conventional CRT) at an interim analysis (median follow-up of 59 months). The researchers nevertheless note a 41% reduction in device battery depletion over 7 years in the adaptive CRT group, which is probably attributable to decreased LV pacing. Moreover, post-hoc analyses indicated a significant decrease in the primary outcome among patients with ≥85% synchronized LV pacing, an exploratory finding that remains to be confirmed.
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