Impact of Left Atrial Appendage Flow Velocity on Thrombus Resolution and Clinical Outcomes in Patients with Atrial Fibrillation and Silent Left Atrial Thrombi: Insights from the LAT Study.

AIMS: Blood stasis is crucial in developing left atrial (LA) thrombi. LA appendage peak flow velocity (LAAFV) is a quantitative parameter for estimating thromboembolic risk. However, its impact on LA thrombus resolution and clinical outcomes remains unclear.

METHODS AND RESULTS: The LAT study was a multicenter observational study investigating patients with atrial fibrillation (AF) and silent LA thrombi detected by transesophageal echocardiography (TEE). Among 17,436 TEE procedures for patients with AF, 297 patients (1.7%) had silent LA thrombi. Excluding patients without follow-up examinations, we enrolled 169 whose baseline LAAFV was available. Oral anticoagulation use increased from 85.7% at baseline to 97.0% at the final follow-up (p < 0.001). During 1-year, LA thrombus resolution was confirmed in 130 (76.9%) patients within 76 (34-138) days. Conversely, 26 had residual LA thrombi, 8 had thromboembolisms, and 5 required surgical removal. These patients with failed thrombus resolution had lower baseline LAAFV than those with successful resolution (18.0 [15.8-22.0] vs. 22.2 [17.0-35.0], p = 0.003). Despite limited predictive power (area under the curve, 0.659; p = 0.001), LAAFV ≤20.0 cm/s (best cutoff) significantly predicted failed LA thrombus resolution, even after adjusting for potential confounders (odds ratio, 2.72; 95% confidence interval, 1.22-6.09; p = 0.015). The incidence of adverse outcomes including ischemic stroke/systemic embolism, major bleeding, or all-cause death was significantly higher in patients with reduced LAAFV than in those with preserved LAAFV (28.4% vs. 11.6%, log-rank p = 0.005).

CONCLUSIONS: Failed LA thrombus resolution was not rare in patients with AF and silent LA thrombi. Reduced LAAFV was associated with failed LA thrombus resolution and adverse clinical outcomes.