Lower rate limit for pacing by cardiac resynchronization defibrillators: Should lower rate programming be reconsidered?

BACKGROUND: No real-world large database associates lower rate limit (LRL) programming and survival of subjects with cardiac resynchronization therapy-defibrillators (CRT-Ds). OBJECTIVE: The purpose of this study was to test the hypothesis that lower LRL programming is independently associated with survival, and that LRL and heart rate score (HrSc) are associated. METHODS: All dual-chamber CRT-D devices in the Remote Patient Monitoring (RPM) ALTITUDE database (2006-2011) were queried. Baseline HrSc was defined as the percentage of all atrial sensed and paced beats in the tallest 10-beat histogram bin postimplant. LRL was assessed during repeated RPM uploads. Using a Cox model multivariable analysis, relationships between LRL, survival, HrSc, and other variables were evaluated. Survival was determined by query of death indices. RESULTS: Data analyzed included 61,881 subjects (mean follow-up 2.9 years). LRL ranged from 40 to 85 bpm. Baseline lower LRL was associated with younger age, less atrial fibrillation, female sex, and lower HrSc (P <.001 for all covariates). Lower LRL was associated with improved survival, with LRL 40 associated with the largest survival benefit. This was significant for all 3 HrSc subgroups (P <.001). An interaction between HrSc and LRL was observed, with the largest survival difference between HrSc groups observed at LRL-40 (P <.001). CONCLUSION: LRL programming and HrSc were associated, and lower values of both were associated with improved survival in a large database of CRT-D subjects. Relationships between survival, LRL programming, and HrSc merit further study.