Discussion We re-evaluated the accuracy of CCT for detecting LAA thrombus in the 726 patients undergoing catheter ablation for AF. TEE identified 57 (7.9%) patients with LAA thrombi, of which 29 (50.9%) were at the LAA ostium and 28 (49.1%) in the LAA. The CCT was less sensitive in detecting LAA-ostium thrombi with smaller maximum diameters and higher LAAMFV. LAA thrombus is thought to form initially inside the LAA, where circulatory stasis is the greatest, and then extends towards the ostium.