Intracardiac Echocardiographic Diagnosis of Thrombus Formation in the Left Atrial Appendage: A Complementary Role to Transesophageal Echocardiography

Background: We sought to develop and validate an intracardiac echocardiography (ICE) imaging strategy for evaluation of left atrial (LA) appendage (LAA) anatomy and function to clarify equivocal findings of LAA thrombus with transesophageal echocardiography (TEE). Methods: A total of 56 patients with ICE imaging of the LAA for thrombus evaluation before atrial fibrillation (AF) or ventricular tachycardia (VT) ablation were included for analysis. Serial views of the LAA were obtained for evaluating anatomic structures and flow as the ICE transducer was advanced from the right ventricular outflow tract to the pulmonary artery. ICE imaging of the LAA was selectively performed in 9 of 56 patients following equivocal findings of thrombus on TEE in order to evaluate the complementary role of ICE to TEE in the diagnosis of LAA thrombus. Results: ICE imaging of the LAA in 56 patients with AF (n = 42) or VT (n = 14) measured the long-(5.0 +/- 1.0 cm) and short-axis dimension (1.8 +/- 0.5 cm), and peak emptying flow velocity (50 +/- 23 cm/s). Of 56 patients, 47 had ICE imaging of LAA with no thrombus. In the remaining 9 patients, 6 had "equivocal" LAA thrombus on TEE, with 3 of these 6 showing marked spontaneous echo contrast (SEC), whereas ICE detected one patient with LAA thrombus and the other 5 without thrombus (two with severe SEC/sluggish flow); the remaining 3 had "high suspicion" for thrombus detected by TEE, whereas ICE detected only one with LAA thrombus. Based on ICE diagnosis, two patients with LAA thrombus had the procedure cancelled, and all others had successful completion of the scheduled procedures. Conclusion: ICE can provide serial assessment, multiple views, and detailed imaging of the LAA to reliably diagnose the presence of thrombus. Our findings support the use of ICE when equivocal TEE findings require confirmation prior to electrophysiological procedures. (Echocardiography 2013;30:72-80)