Echo Rounds: Partial Anomalous Systemic and Pulmonary Venous Return.

Anomalous drainage of a right-sided superior vena cava to the left atrium is a rare variant of systemic venous return anomalies. During the course of investigation for a heart murmur, an asymptomatic child was found to have a superior sinus venosus atrial septal defect with partial anomalous systemic and pulmonary venous drainage. Despite the right superior vena cava overriding the upper end of the atrial septum and draining into the left atrium, the child did not exhibit hypoxemia. Saline contrast transesophageal echocardiography suggested an explanation for the absence of hypoxemia.