Unexpected Severe Cyanosis Following Ventricular Septal Defect Closure and Repair of Right Ventricular Outflow Tract Obstruction.

Ventricular septal defect (VSD) is a common congenital heart defect that often requires surgical closure. We present the case of a seven-month-old infant with a large perimembranous VSD, moderate pulmonary valve stenosis, and hypertrophied right ventricular muscle bundles who failed to wean from cardiopulmonary bypass due to severe cyanosis after VSD closure and muscle bundle resection. An intraoperative transesophageal echocardiogram was performed with an agitated saline test, and a large atrial-level right-to-left shunt was seen. Return to cardiopulmonary bypass revealed an unroofed coronary sinus defect, which had not previously been identified. There was no evidence of a persistent left superior vena cava. Closure of the orifice of the coronary sinus eliminated the shunt, enabling successful weaning from cardiopulmonary bypass, and the patient was subsequently discharged home.