Cor triatriatum is a congenital anomaly in which the left atrium is divided into two parts by a fold of tissue, a membrane or a fibromuscular band. Rarely, it is associated with a persistent left superior vena cava draining into a dilated coronary sinus, which can cause left ventricular inflow obstruction. Even after standard surgical resection of the cor triatriatum membrane, obstruction can persist. We report the case of a 21 year old female with cor triatriatum, diagnosed on routine physical exam. She underwent a novel approach, combining concomitant membrane resection with unroofing and patch enlargement of the coronary sinus, preserving the left superior vena cava. We present a review of this rare entity and the treatment options.