Exploring Left Atrial Appendage Thrombi in Large Vessel Occlusion Stroke by Cardiac CT: Thrombus Features, LAA Characteristics and the Impact of Direct Oral Anticoagulation.

Background: Large vessel occlusion (LVO) strokes account for a significant proportion of ischemic strokes and are often cardioembolic in origin, particularly following atrial fibrillation (AF) with thrombus formation in the left atrial appendage (LAA). Although direct oral anticoagulation (DOAC) therapy reduces stroke risk in AF, anatomical and flow-related factors may still allow thrombi to form and persist, revealing the limitations of anticoagulation in high-risk patients. Examining structural and hemodynamic factors contributing to thrombus persistence is essential for optimizing patient management. Methods: We retrospectively analyzed 169 AF patients with LVO stroke who underwent cardiac CT (cCT) during acute stroke assessment. Patients were categorized based on the presence or absence of persistent LAA thrombi and further stratified by DOAC status. LAA volume, blood stasis and left ventricular (LV) diameter were measured. Thrombi were assessed using Hounsfield Unit (HU) analysis to evaluate potential differences in thrombus composition. Logistic regression analysis was performed to identify independent predictors of thrombus persistence with adjustment for DOAC therapy. Results: Persistent LAA thrombi were identified in 23 patients (13.6%). Patients with thrombi had significantly higher rates of stasis (p = 0.004), larger left ventricular diameters (p = 0.0019) and higher LAA volumes (p = 0.004). When adjusted for DOAC therapy, larger LAA volume (OR 1.05, p = 0.011), presence of LAA stasis (OR 6.14, p = 0.013) and increased LV diameter (OR 1.06, p = 0.006) were independent predictors of thrombus persistence. Thrombus size and HU values did not differ significantly between DOAC and non-DOAC groups. Notably, 30.4% of patients with persistent thrombi were on adequate DOAC therapy. Conclusions: LAA volume, stasis and LV enlargement predict thrombus persistence in the LAA of AF patients with LVO stroke, even under adequate DOAC therapy. These findings highlight the potential need for alternative antithrombotic strategies, including interventional LAA occlusion, and warrant further investigation into individualized stroke prevention in high-risk AF populations.