Pericardial Effusion in the Transverse Sinus

Abstract

A 51-year-old woman with dyspnea on exertion was referred for echocardiography. The patient’s heart rhythm was sinus. Transthoracic echocardiography (TTE) showed normal left ventricular size and systolic function (ejection fraction = 55%), normal right ventricular size and systolic function, severe rheumatic mitral stenosis (the orifice area by direct planimetry = 1.2 cm²), mild mitral regurgitation, mild-to-moderate aortic regurgitation, and mild tricuspid regurgitation with normal systolic pulmonary artery pressure (the estimated pulmonary artery pressure = 31 mm Hg). Transesophageal echocardiography, performed for a better assessment of the mitral valve, confirmed the TTE findings and the absence of a left atrial appendage (LAA) clot. It also demonstrated pericardial effusion around the LAA and a space between the left atrium (LA) in the posterior view, the ascending aorta in the anterior view, and the pulmonary artery in the anterolateral view, suggesting effusion in the transverse sinus (TS).

We present this case to emphasize the significance of recognizing this anatomy. Pericardial sinuses are formed by the reflection of the pericardium where the great vessels enter the pericardial sac. The TS is posterior to the aortic and pulmonary trunk and above the LA. (1) The anatomic recognition of the TS is crucial, specifically during interventional procedures because the first herald of complications can be a fluid collection in the TS. These procedures have a broad spectrum extending from intra-LA to great vessel ones. (2,3) Thus, a clinician who performs intraprocedural echocardiography should be familiar with the TS anatomy and know that the fat and parts of normal structures, such as the LAA, can mimic thrombi and masses in the TS. (1,4) Diagnosing these conditions can determine a physician’s decision-making ability. Furthermore, the occurrence of pericardial effusion in some systemic diseases has been reported as a first sign. (5) The significant differential diagnosis of effusion in the TS is the pseudoaneurysm of aortomitral intervalvular fibrosis owing to cardiac surgery or infective endocarditis. The absence of flow in the color Doppler study suggests effusion in the TS. (1) Clinicians should, therefore, be au fait with the TS anatomy to manage patients intraprocedurally and diagnose complications.