Incidence and predictors of left atrial thrombus development in patients scheduled for repeat catheter ablation for atrial fibrillation: Is transesophageal echocardiography always mandatory?

Introduction: The risk of 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. Methods: 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 which factors were associated with safety outcomes and requirements for thrombi screening. Results: All patients underwent at least one imaging examination to screen for thrombi in the first session, but the examination rate decreased to 476 patients (77%) before the repeat procedure. 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 procedure, respectively. Three patients (0.5%) developed LA thrombi at repeat ablation due to identifiable causes, and no patients had thromboembolic events when no imaging evaluation was performed. Multivariate analysis revealed that repeat ablation >180 days, non-paroxysmal atrial arrhythmias, and lower left ventricular ejection fraction were predictors of the risk of thrombus development. Conclusions: The risk development of thrombus at repeat ablation for AF was low. There needs to be a risk stratification for the requirement of imaging screening for thrombi at repeat ablation for AF.