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.