Incidence of Left Atrial Thrombus Development and Imaging Approach in Patients Scheduled for Repeat Catheter Ablation for Atrial Fibrillation.

The risk for developing left atrial (LA) thrombi after initial catheter ablation for atrial fibrillation (AF) and requirements for imaging evaluation for thrombi screening at repeat ablation is unclear. This study aimed to assess the occurrence of thrombus development and frequency of any imaging study evaluating thrombus formation during repeat ablation for AF. Of 2,066 patients undergoing initial catheter ablation for AF with uninterrupted oral anticoagulation, 615 patients underwent repeat ablation after 258.0 (105.0-882.0) days. We investigated the factors associated with safety outcomes and requirements for thrombus screening. All patients underwent at least one imaging examination to screen for thrombi in the initial session; however, the examination rate decreased to 476 patients (77%) before the repeat session. The frequency of imaging evaluations was 5.0%, 11%, 21%, 84%, and 91% for transesophageal echocardiography and 18%, 33%, 49%, 98%, and 99% for any imaging modality at repeat ablation performed ≤60 days, ≤90 days, ≤180 days, >180 days, and >1 year after the initial session, respectively. Three patients (0.5%) developed LA thrombi at repeat ablation due to identifiable causes, and no patients experienced thromboembolic events when no imaging evaluation was performed. Multivariate analysis revealed that repeat ablation performed after >180 days, non-paroxysmal atrial arrhythmias, and lower left ventricular ejection fraction were predictors of thrombus development and severe spontaneous echocardiography contrast. In conclusion, the risk for thrombus development at repeat ablation for AF was low. There needs to be a risk stratification of the imaging screening for thrombi at repeat ablation.