In patients in which LAA thrombus is detected on TEE, cardioversion postponed, and OAC continued for another 4-12 weeks, to allow thrombus resolution or endothelization, we suggest that a decision on whether a repeat TEE is performed should be individualized (Ungraded consensus-based statement). Cardioversion of AF of 48 h Duration or Less: The duration of AF necessary for development of thrombus is not clear. Therefore, the threshold of AF duration below which pre-cardioversion anticoagulation can be safely avoided is not known. It is common practice to cardiovert without TEE or prolonged pre-cardioversion anticoagulation if AF is of short duration (< 48 h). The problem with this approach is the presence of left atrial thrombus on TEE in up to 14% of patients with AF of short duration in observational studies.264,265 In addition, the high prevalence of asymptomatic AF makes determining the exact duration of AF dif cult.266 If there is uncertainty about precise time of AF onset, then such patients should be managed as if AF > 48 h. A recent Finnish observational study of 5,116 successful cardioversions in 2,481 patients with acute (< 48 h) AF showed low incidence of stroke/thromboembolism during the 30 days following cardioversion, even without perioperative anticoagulation (0.7%).267 These results concur with low rates of stroke/thromboembolism in observational studies (Table 8).234,267-272 However, there is lower incidence of stroke/thromboembolism with cardioversions performed during anticoagulation (0.1% vs 0.7%; P .001), and with anticoagulation vs no anticoagulation in patients with a CHA2DS2-VASc score of $ 2 (0.2% vs 1.1%; P .001). 