Biatrial or left atrial drainage of the right superior vena cava: anatomic, morphogenetic, and surgical considerations--report of three new cases and literature review.

Since the posterior wall of the right superior vena cava (RSVC) is contiguous with the anterior wall of the right upper pulmonary veins, a localized defect in this common wall may create a cavopulmonary venous confluence without eliminating the normal connection of the same right pulmonary veins with the left atrium (LA). Through this defect, blood of the unroofed right pulmonary veins will drain into the RSVC and right atrium (RA), and blood from the RSVC may shunt into the right pulmonary veins and LA. Hemodynamically, the RSVC will become biatrial. If the RSVC blood flows preferentially into the LA, its right atrial orifice will become stenotic or even atretic. If atretic, the normally positioned RSVC will drain entirely into the LA. In this report, we present the clinical and anatomical findings of two postmortem cases with biatrial drainage of the RSVC. We also document the clinical, echocardiographic, angiocardiographic, and surgical data of a living patient with left atrial drainage of the RSVC and tetralogy of Fallot with pulmonary atresia. The relevant literature and surgical treatment are reviewed, and the morphogenesis of the biatrial and left atrial RSVC is considered.