Transverse sinus fat pad may masquerade as left atrial appendage thrombus

Transesophageal echocardiography (TEE) is a commonly utilized investigation in patients with atrial fibrillation to study the left atrial appendage (LAA) and exclude an appendage thrombus before proceeding with cardioversion. Although TEE is considered the procedure of choice for this purpose, it may sometimes offer a limited specificity due to common anatomical variations associated with either the LAA or the adjoining cardiac structures. We herewith present a patient with atrial fibrillation who underwent TEE and was found to have an echodensity in the vicinity of left atrial appendage that mimicked a thrombus. A careful further evaluation however confirmed that the echodensity actually was consistent with a dense epicardial fat pad. TEE imaging evaluation in different planes and angulations is thus paramount in establishing a correct diagnosis. Supplemental information from other imaging modalities such as cardiac computed tomography may sometimes offer an additional value, especially if the diagnosis remains unclear.