In a re-analysis of the ASSERT study,388 the increase in the risk of stroke occurred only when the longest duration of the various episodes of detected AHREs was > 24 h. The largest dataset of patients with CIED-detected AHREs was analyzed in the Stroke Prevention Strategies Based on Atrial Fibrillation Information From Implanted Devices [SOS AF] project, with a pooling of 3 prospective studies (Phase IV Long Term Observational Study of Patients Implanted With Medtronic CRDM Implantable Cardiac Devices [PANORAMA], Italian Clinical Services Project, and A Prospective Study of the Clinical Signi cance of Atrial Arrhythmias Detected by Implanted Device Diagnostics [TRENDS]) resulting in During a median follow-up of 24 months, 43% of an unselected cohort of patients with implanted devices experienced $ 1 day with $ 5 min of AHRE burden, and a 1-h threshold of AHRE burden was associated with an HR for ischemic stroke of 2.11 (95% CI, 1.22-3.64; P .008), although the absolute risk of ischemic stroke in patients with AHREs was low (0.39% annual rate in the whole cohort). Similarly, the found that an AHRE burden of 5.5 h in a day, in a 30-day period, was associated with a twofold increase in the adjusted risk of stroke (absolute risk of thromboembolism around 1.8% per year).383 Integration of AHRE presence, duration, or burden ($ 5 min or $ 24 h) into risk scores for thromboembolism may modestly improve c-statistics of both the CHADS2 and CHA2DS2-VASc scores for predicting stroke.389 The clinical signi cance of AHRE is presumably different from that of clinically identi ed AF since the latter, detected using conventional surface ECG methods, corresponds to a much higher AF burden as compared with patients with AHRE detected by continuous monitoring via a CIED.370,372 The actual rates of stroke or systemic embolic events reported in studies evaluating CIED-detected AHREs are often lower than what would be predicted by CHADS2 and CHA2DS2-VASc scores, and this may be related to concurrent treatment with OACs in each study, risk of under-reporting, and confounding. 