Obstructed Supramitral Inflow: Cor Triatriatum Sinister Presentation in Adulthood.

Cor triatriatum is a rare congenital heart defect that occurs when a fibromuscular membrane divides the atrium into two chambers, which may impair blood flow to the ventricle. When it does, the symptoms usually manifest during infancy or early childhood. In this E-challenge, though, the case of a 40-year-old man is reviewed whose symptoms of shortness of breath progressed over the years and were attributed to the diminished mitral valve inflow due to the restricted cor triatriatum sinister associated with pulmonary hypertension, tachycardia-bradycardia syndrome, and atrial fibrillation. Despite routine preoperative evaluation, intraoperative transesophageal echocardiography was used to more accurately evaluate cor triatriatum sinister's morphology, hemodynamic significance, and associated anomalies.