Background: The risk factors for left atrial (LA) thrombus formation in patients with atrial fibrillation (AF) have been well characterized, but it is unclear why occasionaly thrombi persist despite effective anticoagulation.
Methods: We screened our echo lab registry from 1995-2010 for patients with AF who had at least two trans-esophageal (TEE) studies spaced 28 to 140 days apart and who received warfarin therapy with therapeutic INR values above 2 between the two repeat studies, excluding 775 patients with AF and repeated TEEs who did not meet these criteria. We eventually selected 14 such patients with an LA thrombus on the initial TEE but subsequent resolution on following one (Group 1) and 13 patients with persistent atrial thrombus on both TEE studies (Group 2), and compared their clinical and echocardiographic characteristics.
Results: The mean time gap between the two TEE studies was 65±44 days. Notably, 1/14 patients in group 1 and 2/13 patients in group 2 had cardiac amyloidosis, and one patient in group 2 but none in group 1 had rheumatic heart disease. Group 2 patients had smaller left atria and ventricles than group 1 and lower LA velocities. The values in the table represent absolute numbers (percentage) or median (25th-75th percentiles).
Conclusions: LA thrombus persisted in patients with atrial fibrillation despite on-target warfarin therapy in a high proportion of our patients (13/27), justifying the need for a repeat TEE to exclude persistent thrombus prior to cardioversion or ablation in patients with initial LA thrombus. The paradoxical finding of a smaller cardiac size in patients with persistent LA thrombus remains unexplained and warrants further evaluation by expanding the study database.
