High Initial Heart Rate Score is an Independent Predictor of New Atrial High-Rate Episodes in Pacemaker Patients with Sinus Node Dysfunction

Abstract Background Heart Rate Score (HRSc), the percent of atrial beats in the largest paced/sensed 10-bpm histogram bin recorded in cardiac devices, is a metric of chronotropic incompetence. It remains uncertain if HRSc independently predicts atrial high-rate episodes (AHREs) in patients with sinus node dysfunction (SND) undergoing pacemaker (PM) implantation. Objective To determine the relationship between initial HRSc post-PM implant and new-onset AHREs in patients with SND. Methods The cohort included patients with Boston Scientific PMs implanted for SND from 2012-2021 at Cleveland Clinic, University of Occupational and Environmental Health, Japan, Kyushu Rosai Hospital, and JCHO Kyushu Hospital. Patients were excluded if they had atrial fibrillation before PM implant or AHREs in the initial 3-months post-implant. Subsequent AHREs post-implant (>1% of atrial beats>170 bpm) were evaluated. Results Over 48.9 (IQR 25.8-50.4) months, 136 consecutive PM patients (age 75±10 years, 42% male) were followed. The median initial HRSc was 73(55-86)%. AHREs developed in 28/136 (21%). Although %RA pacing and HRSc correlated, rate-responsive pacing was associated with a HRSc only in the patients with high %RA pacing. Patients with HRSc≥80% had higher occurrence of AHREs than those with HRSc<80% (p=0.01, log-rank test). After adjusting for age, race, comorbidities, left ventricular ejection fraction, left atrial diameter, %RA/RV pacing, and rate-response programming, HRSc (HR:2.84, 95% CI:1.17-6.92; P=0.02) and male sex (HR:2.55, 95% CI:1.15-6.19; P=0.04) were independent predictors of AHREs. Conclusion HRSc≥80% independently predicted new-onset, device-determined AHREs for patients undergoing PM implant for SND. HRSc may have prognostic and therapeutic implications.