Addition of minute ventilation to rate-response pacing improves heart rate score more than accelerometer alone.

Background: Heart rate score (HRSc) ≥70%, a novel parameter, predicts risk of mortality in patients with implantable cardioverter-defibrillators and identifies patients who have survival benefit with DDDR vs DDD pacing.

Objective: The purpose of this study was to determine if DDDR pacing lowers HRSc, and a blended sensor with minute ventilation (MV) and accelerometer (XL) improves HRSc more than accelerometer (XL) alone in patients requiring pacemakers (PMs).

Methods: HRSc, the percentage of all beats in the tallest 10-beat/min device histogram bin, was calculated. Data from the Limiting Chronotropic Incompetence for Pacemaker Recipients Study, a prospective randomized trial of PM patients, comparing XL to blended-sensor (XL + MV) rate-responsive pacing, were analyzed retrospectively for HRSc changes from baseline. The relationship of patient activity (sensor-detected from device memory) to HRSc was examined.

Results: Of the 501 randomized patients, 215 (43%) patients had HRSc ≥70% during DDD pacing at baseline. In these patients, HRSc decreased after DDDR programming by 14.2%, while it increased by 0.4% in those with baseline HRSc <70% (n = 286) (HRSc ≥70% vs HRSc <70%; P < .01). No differences were detected between the 2 randomized sensor-based groups at baseline. Blended-sensor (MV + XL) programming reduced HRSc more than the XL sensor alone (MV + XL: 18% vs XL: 10%; P < .001). No correlation was observed between patient activity and HRSc (correlation = -0.14; P = .07).

Conclusion: HRSc improved (reduced) with rate-response (DDDR) programming in PM patients with high HRSc during DDD pacing. Blended sensors (MV + XL) improved HRSc more than XL alone. HRSc does not correlate with patient activity levels, suggesting that other patient factors determine this parameter. This programming approach needs to be investigated prospectively in a PM outcomes trial.