Adult Cor Triatriatum Found by Chance at the Onset of Myocardial Infarction

: Cor triatriatum sinister is a rare congenital heart disease in which the left atrium is divided into 2 chambers by a membrane, causing resistance to the blood flow to the left ventricle. The onset of symptoms depends upon the effective size of the orifice in the membrane and the associated heart disease. Our case is a 67-year-old woman with cor triatriatum found by chance at the onset of myocardial infarction. Coronary artery bypass surgery and excision of the membrane were successfully performed. Preoperative left ventricular dysfunction was improved after surgery. Imaging examinations such as enhanced computed tomography(CT) and magnetic resonance imaging(MRI) were useful for selecting surgical approach.