Introduction
The anatomy of pericardial cavity consists of two sinuses; transverse and oblique sinuses. A recess in pericardial cavity adjacent to pulmonary vein and also another one in transverse sinus near pulmonary artery have been detected in 70-80% of general population. Transverse sinus (TS) is located anterior to the left atrium (LA) and almost posterior to the aortic root. In some people the tip of the LA appendage (LAA) may be located posterior, inferior or even into the pericardial sinus. Many anatomic variations in LAA have been depicted in the literature. Sometimes puncture of the inter-atrial septum may enter the transverse pericardial sinus and endanger the aortic root[1, 2].
Pericardial fat pad in transverse sinus adjacent to LAA is a rare condition that may resemble LAA thrombosis especially in suspected cases. Atrial fibrillation and severe mitral stenosis (MS) change the morphology and geometry of the LA/LAA. LAA itself has many complex variations.
Herein we present a rare anatomic variation in a patient with severe MS who was candidate for percutaneous transvenous mitral commissurotomy (PTMC) called transverse sinus fat pad (TSFP). In trans-esophageal Echocardiographic (TEE) views even an expert operator may be mistaken at fist if he or she is not familiar with TSFP.