Comprehensive Left Atrial Appendage Optimization of Thrombus Using Surface Echocardiography: The CLOTS Multicenter Pilot Trial

Background: The aim of this study was to determine the ability to identify thrombus within the left atrial appendage (LAA) in the setting of atrial fibrillation (AF) using transthoracic echocardiography (TTE). In AF, the structure and function of the LAA has historically been evaluated using transesophageal echocardiography (TEE). The role of TTE remains undefined. Methods: The Comprehensive Left Atrial Appendage Optimization of Thrombus (CLOTS) multicenter study enrolled 118 patients (85 men; mean age, 67 ± 13 years) with AF of >2 days in duration undergoing clinically indicated TEE. On TEE, the LAA was evaluated for mild spontaneous echo contrast (SEC), severe SEC, sludge, or thrombus. Doppler Tissue imaging (DTI) peak S-wave and E-wave velocities of the LAA walls (anterior, posterior, and apical) were acquired on TTE. Transthoracic echocardiographic harmonic imaging (with and without intravenous contrast) was examined to determine its ability to identify LAA SEC, sludge, or thrombus. Results: Among the 118 patients, TEE identified 6 (5%) with LAA sludge and 2 (2%) with LAA thrombi. Both LAA thrombi were identified on TTE using harmonic imaging with contrast. Anterior, posterior, and apical LAA wall DTI velocities on TTE varied significantly among the 3 groups examined (no SEC, mild SEC, severe SEC, sludge or thrombus). An apical E velocity ≤ 9.7 cm/s on TTE best identified the group of patients with severe SEC, sludge, or thrombus. An anterior S velocity ≤ 5.2 cm/s on TTE best identified the group of patients with sludge or thrombus. Conclusions: The CLOTS multicenter pilot trial determined that TTE is useful in the detection of thrombus using harmonic imaging combined with intravenous contrast (Optison; GE Healthcare, Milwaukee, WI). Additionally, LAA wall DTI velocities on TTE are useful in determining the severity of LAA SEC and detecting sludge or thrombus.