OBJECTIVES: In patients with atrial fibrillation (AF), most thrombus forms in the left atrial appendage (LAA). However, the relation of LAA morphology with LAA thrombus is unknown.
METHODS: We prospectively enrolled 633 consecutive patients who were candidates for catheter ablation for symptomatic drug-resistant AF. Transesophageal echocardiography (TEE) was performed to assess LAA thrombus. LAA structure was assessed by three-dimensional TEE. LAA orifice area, depth, volume, and number of lobes were measured on reconstructed three-dimensional images. Clinical characteristics and echocardiographic measures were compared to determine variables predicting LAA thrombus.
RESULTS: Excluded were 69 (10.9%) patients who met the exclusion criteria. Finally, this study comprised 564 patients in whom LAA thrombus was observed in 36 (6.4%) patients. Multivariate analysis revealed CHADS2 score (P=0.002), left ventricular ejection fraction (P=0.01), degree of spontaneous echo contrast (P=0.02), left atrial volume (P=0.02), and number of LAA lobes (P<0.001) to be independently associated with thrombus formation. Most patients with LAA thrombus (32/34, 94.4%) had â‰¥3 LAA lobes, whereas LAA thrombus was observed in only 2 (0.7%) of 296 patients with 1 or 2 lobes. LAA volume significantly decreased in patients maintaining sinus rhythm after catheter ablation (P=0.0009). Number of LAA lobes did not change in any patient.
CONCLUSIONS: Complex LAA morphology characterized by an increased number of LAA lobes was associated with the presence of LAA thrombus, independently of clinical risk and blood stasis. This study suggests that LAA morphology might be a congenital risk factor for LAA thrombus formation in patients with AF. Morgan Burnett Womens Jersey