Atrial fibrillation burden and oral anticoagulation: a context-dependent framework for net clinical benefit beyond binary AF definitions

Atrial fibrillation (AF) is a major risk factor for ischaemic stroke, and oral anticoagulation (OAC) effectively reduces thromboembolic risk in patients with clinically diagnosed AF. With the expanding use of continuous rhythm monitoring and wearable devices, increasing numbers of device-detected atrial arrhythmias are being identified, challenging the traditional binary approach to AF diagnosis and anticoagulation decision-making. AF burden, commonly defined as the proportion of monitored time spent in AF during a defined monitoring period, has emerged as a quantitative measure of AF exposure. Observational studies using continuous monitoring, including ASSERT, TRENDS, and KP-RHYTHM, consistently demonstrate that increasing AF burden is associated with progressively higher absolute risks of ischaemic stroke and systemic embolism. However, patients with low AF burden generally have relatively low absolute event rates. Randomized trials such as LOOP, ARTESiA, and NOAH-AFNET 6 further evaluated anticoagulation in patients with device-detected or subclinical AF. Collectively, these studies suggest that, in low-burden AF populations, reductions in thromboembolic events with OAC may be offset by increased bleeding risk, resulting in limited overall net clinical benefit. Current evidence indicates that AF burden alone is unlikely to provide sufficient guidance for anticoagulation decisions. Instead, the net clinical benefit of OAC appears to depend on the interaction among AF burden, thromboembolic risk, bleeding risk, and patient-specific clinical factors. This review summarizes current evidence on AF burden and discusses how AF burden, thromboembolic risk, and bleeding risk may jointly influence the net clinical benefit of anticoagulation.