Left Atrial Appendage Function vs. Geometry: Predicting Thrombus Risk in Atrial Fibrillation

Objective: Left atrial appendage (LAA) thrombus and/or spontaneous echo contrast (SEC) may occur despite adequate anticoagulation in patients with atrial fibrillation (AF). This study aimed to evaluate whether mitral annular geometry (annular area and sphericity) and the angle between the mitral annular plane and the Coumadin ridge are associated with LAA thrombus and/or SEC in anticoagulated patients with AF.
Method: We retrospectively enrolled 133 consecutive patients with AF (≥2 years’ duration) receiving anticoagulant therapy who were referred for ablation or cardioversion. Preprocedural TEE provided measurements of LAA fractional area change (FAC), flow velocity, MAP–Coumadin ridge angle, mitral annular area, and sphericity. Logistic regression was used to identify independent predictors of thrombus/SEC.
Results: LAA thrombus/SEC was present in 44 patients (33.1%). Compared with unaffected patients, those with thrombus/SEC had lower LAA FAC (0.26±0.13 vs. 0.37±0.12, P < 0.001), a larger mitral annular area (992.50±210.81 vs. 898.75±159.04 mm², P = 0.009), lower LVEF, more frequent heart failure, and larger cardiac dimensions. The MAP–LAA angle and sphericity were similar between the groups. On multivariable analysis, LAA FAC was the sole independent predictor (OR 0.49 per 10% increment, 95% CI 0.32–0.70, P < 0.001; AUC 0.72, cutoff 0.20, sensitivity 44%, specificity 96%). Mitral annular area showed modest discriminatory ability (AUC 0.64) and did not significantly improve the model when combined with FAC (P = 0.39).
Conclusion: LAA FAC is a strong independent predictor of thrombus/SEC in anticoagulated patients with AF, underscoring the primacy of appendage contractile function over geometric parameters. Mitral annular enlargement provides only marginal incremental value, whereas the MAP–LAA angle does not contribute. Routine measurement of LAA FAC provides a simple, reproducible echocardiographic tool for thrombus risk stratification.

Keywords: Atrial fibrillation, fractional area change, left atrial appendage, mitral annulus, thrombosis.