Atrial high-rate episodes and thromboembolism in patients without atrial fibrillation: The West Birmingham Atrial Fibrillation Project

Background: Patients with cardiac implantable electronic device (CIED) developing atrial high-rate episodes (AHRE) have a significant risk of thromboembolic events (TEs), but risk factors have been scarcely investigated. Objectives: To analyze risk factors for TEs in a contemporary cohort of patients with CIED. Methods: Consecutive non-AF patients without anticoagulation at baseline were followed up after the CIED implantation. The role of newly-developed AHRE and other risk factors for TEs were analyzed using a time-dependent Cox regression model and Kaplan-Meier analysis with log-rank tests. Results: A total of 594 CIED patients were followed up for a mean of 4.2 years: 175 developed AHRE (29.5%; incident rate [IR] 8.80% per patient-year). Of those, 33 experienced TEs (5.5%; IR 1.38% per patient-year). Incidence of TEs was low in patients with a CHA ₂DS ₂-VASc score < 2 (male)/<3 (female) (AHRE vs. no-AHRE, 0.60% vs. 0.00% per patient-year, p = 0.469) and high in those with score ≥ 2 (male)/≥3 (female) (AHRE vs. no-AHRE, 2.12% vs. 1.36% per patient-year, p = 0.209), regardless of the AHRE presence. AHRE was not significantly associated with TEs (hazard ratio [HR], 1.46 [0.64–3.33]). There was no temporal relationship between AHRE and TEs. Baseline CHA ₂DS ₂-VASc score was independently associated with TEs (HR, 1.41 [1.13–1.75]) on multivariate analysis, but not AHRE. Conclusions: Thromboembolic risk in patients with CIED is mainly driven by comorbidity burden, i.e., CHA ₂DS ₂-VASc score, rather than AHRE per se. Decision-making on stroke prevention needs to focus on comorbidity burden and not merely on the presence or absence of AHRE in CIED patients.