Anomalous systemic venous drainage in truncus arteriosus - An unusual association.

Truncus arteriosus (TA) is a major cyanotic heart malformation infrequently associated with aortic arch interruption and isolation of the branch pulmonary artery. Anomalous superior vena caval drainage to the left atrium (LA) is hitherto unreported in TA. In a 45-day-old infant diagnosed with TA and cyanosis, anomalous drainage of the right superior vena cava into the LA was not identified preoperatively or intraoperatively. It was detected postoperatively due to persistent hypoxemia. The anomaly posed unique challenges in the subsequent management. This case report highlights the unusual association of systemic venous drainage in TA.