Real-world incidence and predictors of LAA thrombus in patients scheduled for an elective atrial tachyarrhythmia ablation.

Introduction Transoesophageal echocardiography (TOE) is routinely performed before catheter ablation of atrial tachyarrhythmias to exclude left atrial appendage (LAA) thrombus. Because of its very low prevalence in anticoagulated patients, the true incidence of LAA thrombus on oral anticoagulants remains difficult to establish, and the contribution of additional clinical and procedural risk factors requires further evaluation. Methods This retrospective observational study pooled more than six years of data from two high-volume electrophysiology centres, comprising more than six thousand consecutive patients referred for an atrial tachycardia/fibrillation ablation. The aim was to identify and refine predictors of LAA thrombus formation and to explore whether thrombus occurrence in atrial fibrillation (AF) is predominantly associated with suboptimal anticoagulation adherence. Clinical characteristics and established predictors of impaired LAA flow were collected and assessed using univariate analyses. Warfarin adherence was verified by three in-range INR measurements within three weeks before the procedure. Results A total of 6351 TOEs were included. The cohort comprised 1912 women (30 percent). The mean age was 63 ± 13 years and a mean BMI of 29 ± 3 kg/m². LAA thrombus was identified in 22 patients (0.35 percent). Higher preprocedural CHA2DS2-VASc scores and persistent AF were significantly associated with thrombus formation (p = 0.029 and <0.05, respectively), whereas other clinical parameters, including sex, age and BMI, were not significant in the univariate model. Importantly, LAA thrombus was also observed in patients with low CHA2DS2-VASc scores (≤ 1; n = 5). One-third of thrombus cases occurred in patients treated with warfarin, a finding that remained highly significant (p < 0.001). The rate of thrombus was approximately ten-fold lower in patients receiving direct oral anticoagulants (DOACs) compared with warfarin (0.16 percent vs 1.7 percent). These discrepancies may reflect differences in patient selection, with warfarin more often prescribed to individuals at higher thrombotic risk (mean CHA2DS2-VASc of 4.75 for warfarin vs. 2.4 for DOACs) as well as possible suboptimal anticoagulation control or subtherapeutic INR values. Conclusion LAA thrombus is a rare finding before elective catheter ablation. In this large real-world cohort, thrombus was significantly more frequent in patients treated with warfarin compared with DOACs. This difference may reflect underlying selection bias, with warfarin more often used in patients at higher thrombotic risk, as well as potential variability in anticoagulation control despite apparent therapeutic INR values. Further studies are warranted to clarify the relative contributions of these factors.