Reassessing the Programmed Lower Rate Limit for Cardiac Resynchronization Defibrillators-A Commentary

Author(s): Arjun Sharma, Brian Olshansky, Bruce Wilkoff, Mark Richards, Paul Jones, Nicholas Wold, David Persbacher

The programmed lower rate limit (LRL) has not previously been associated with the survival of subjects with cardiac resynchronization defibrillators (CRT D). We hypothesized that lower LRL programming is independently associated with survival, and LRL and heart rate score (HrSc) are associated. 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 atrial sensed and paced beats in the tallest 10 beats histogram bin early post-implant. LRL was assessed during repeated RPM uploads. Relationships between LRL, survival, HrSc, and other variables were evaluated. Survival was determined via Death Indices. Analyzed data 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<0.001 for all covariates). Lower LRL was associated with improved survival with LRL-40 bpm associated with the largest survival benefit. This was significant for all three HrSc subgroups (p<0.001). An interaction between HrSc and LRL was observed; with the largest survival difference between HrSc groups observed at LRL-40(p<0.001). Thus, 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 a controlled prospective study.

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