Adult presentation of cor triatriatum sinister with anomalous coronary venous drainage into the left atrium: A rare congenital abnormality.

Cor triatriatum is a rare congenital heart defect characterized by an abnormal fibromuscular septation. Many cases present in infancy, with adult presentations especially uncommon. Additionally, concomitant anomalous coronary venous drainage into the left atrium is extremely rare, with few cases reported in the literature. We report the case of a 71 year old male with progressive dyspnea on exertion and severe symptomatic aortic valve stenosis who was found on CT angiography to have evidence of an incomplete fibromuscular membrane within the left atrium consistent with cor triatriatum sinister, as well as anomalous coronary venous drainage with the coronary sinus draining into the left atrium. This case highlights the importance of advanced cardiac imaging in discovering rare congenital cardiac anomalies in adults with cardiovascular symptoms as it can aid in diagnostic clarification, procedural planning and cardiovascular interventions. Recognition of these abnormalities is particularly important in patients undergoing structural cardiac evaluation, as there may be implications for procedural planning or management.