Subclinical Atrial Fibrillation Burden and Adverse Clinical Outcomes in Patients With Permanent Pacemakers

Background and Purpose: Unlike clinical atrial fibrillation (AF), the significance of subclinical AF (SCAF) burden in patients with permanent pacemakers has not been fully evaluated. Methods: We investigated whether the SCAF burden was associated with increased risks of composite adverse outcomes, including progression to clinical AF, ischemic stroke, myocardial infarction, heart failure-related hospitalization, or cardiac death, in patients without previous AF. To quantify the 6-month SCAF burden, the total cumulative time spent in SCAF during every 6-month follow-up was summed. Results: During the median 5.2-year follow-up, 496 consecutive permanent pacemaker patients were classified into the no SCAF (no SCAF episode in any device analysis; n=152), low-burden SCAF (6-month SCAF <24 hours in at least one device analysis; n=287), or high-burden SCAF (6-month SCAF ≥24 hours in at least 1 device analysis; n=57) groups. The risk of composite adverse outcomes was greatest in the high-burden SCAF group (P <0.001) and was primarily driven by progression to clinical AF (P <0.001) and ischemic stroke (P <0.001). The presence of high-burden SCAF, which always preceded ischemic stroke events, was independently associated with composite adverse outcomes (odds ratio=20.1 [95% CI, 7.60−52.7],P <0.001) and progression to clinical AF (odds ratio, 36.2 [95% CI, 15.9−87.8],P <0.001).Conclusions: In permanent pacemaker patients without preexisting AF, the presence of high-burden SCAF was closely associated with increased risks of composite adverse outcomes, particularly progression to clinical AF and ischemic stroke. Therefore, prospective studies deserve to be performed on the optimal anticoagulation therapy for permanent pacemaker patients with both high-burden SCAF and high stroke risk.