The transverse pericardial sinus: an unpleasant third wheel

Epicardial and transverse sinus fat pad near left atrium appendage; role of 3D echocardiography

Pericardial fat pad in transverse sinus adjacent to left atrial appendage (LAA) is a rare condition that may resemble LAA thrombosis especially in suspected cases. More Trans-esophageal echocardiography (TEE) angulations and also 3D TEE images are helpful tools to confirm the diagnosis.

Epicardial fat pad within the transverse sinus mimicking a left atrial appendage thrombus

The presence of left atrial thrombus is a contraindication to cardioversion or catheter ablation in patients with atrial fibrillation, due to the increased risk of systemic thromboembolism. Management of this situation includes changes in the anticoagulation regimen and repeat imaging tests. Accurate diagnosis of left atrial appendage thrombus is therefore essential but can sometimes be challenging. Multiple imaging modalities may sometimes be required in the setting of anatomical variations of the left atrial appendage and surrounding structures.

We present the case of a patient awaiting ablation for atypical atrial flutter, who underwent a transthoracic echocardiogram that showed an echodense, mobile structure within the vicinity of the left atrial appendage, suggesting a possible thrombus. A cardiac CT demonstrated the image to correlate with an epicardial fat pad within the transverse sinus.