Cor triatriatum sinister in a 43-year-old man with syncope

Cor triatriatum sinister, a congenital cardiac anomaly involving a fibromuscular membrane that partitions the left atrium into 2 chambers, has been reported in only 0.1% to 0.4% of patients with congenital heart disease. The posterosuperior chamber receives blood from the pulmonary veins, and the anteroinferior chamber contains the left atrial appendage and mitral valve orifice. Most patients are diagnosed with the condition in infancy or childhood; adult cases are rare. We describe a case of cor triatriatum sinister in a 43-year-old man whose only presenting symptom was recurrent syncope. He underwent corrective resection of the membrane and was asymptomatic thereafter. In addition to discussing the patient's case, we review the relevant medical literature.