High initial heart rate score is an independent predictor of new atrial high-rate episodes in pacemaker patients with sinus node dysfunction

Background: Heart rate score (HRSc), the percentage of atrial depolarizations in the largest paced and sensed 10-beats/min histogram bin recorded in cardiac devices, is associated with several adverse outcomes, but it remains uncertain whether HRSc independently predicts atrial high-rate episodes (AHREs) in patients with sinus node dysfunction (SND) undergoing pacemaker (PM) implantation.

Objective: This study aimed to determine whether initial HRSc after PM implantation predicts new-onset AHREs in patients with SND.

Methods: Patients had Boston Scientific PMs implanted for SND from 2012 to 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 implantation or AHREs within 3 months after implantation. Subsequent AHREs after implantation were evaluated and correlated with HRSc.

Results: During 48.9 (interquartile range, 25.7-50.4) months, 130 consecutive PM patients (76 ± 10 years; 40% male) had a median initial HRSc of 74% (57%-86%). AHREs defined by >1%, >6 h/d burden, and atrial tachycardia response events >24 hours developed in 27 of 130 (21%), 15 of 130 (12%), and 9 of 130 (7%), respectively. For each definition, patients with HRSc ≥80% had higher occurrence of AHREs than those with HRSc <80% (both P = .008, log-rank test). After adjustment for age, race, comorbidities, left ventricular ejection fraction, left atrial diameter, and cumulative percentage of right atrial and right ventricular pacing, initial HRSc ≥80% (hazard ratio, 3.33; 95% CI, 1.35-8.18; P = .009) and male sex (hazard ratio, 2.59; 95% CI, 1.06-6.33; P = .04) independently predicted AHREs.

Conclusion: HRSc ≥80% is associated with new-onset, device-determined AHREs for patients undergoing PM implantation for SND. HRSc may have prognostic and therapeutic implications.