Role of atrial fibrillation burden in assessing thromboembolic risk

Currently available data have demonstrated that many patients without a clinical history of AF will have short episodes of AF detected on pacemaker and ICD interrogations. The clinical implications of short (lasting seconds to minutes) subclinical episodes of AF and the optimal cutoff time for treating devicedetected AF episodes remain unclear. It is likely, however, that continuous AF episodes lasting more than a few hours, but <48 hours, do carry an increased risk of thromboembolic stroke, with a risk profile that likely varies based on a patient's underlying substrate and thromboembolic risk factors. Our current approach to thromboembolic prophylaxis is fraught with uncertainty and contradiction. The time honored assumption that 48 hours of AF is required for thrombus development has formed a first principle of AF management for decades. Emerging data have challenged this premise and, in fact, have drawn into question the importance of proximate AF for stroke risk. If there is a population for whom AF burden significantly contributes to stroke risk, it is likely those patients with few non-AF-related stroke risk factors. The availability of sophisticated, continuous remote monitoring and new, rapidly acting oral anticoagulants affords the opportunity to formally test a strategy of tailored anticoagulation and the hypothesis that some lower-risk patients may be able to stop and start anticoagulation based on the pattern of AF.