Divided left atrium (cor triatriatum) in the setting of common atrium

Cor triatriatum is commonly used to describe the congenital malformation in which an anomalous fibromuscular shelf divides the left atrium. We report the successful surgical repair of an extremely rare combination of divided left atrium, virtual absence of the interatrial septum, and anomalous right pulmonary venous connection in a 7 year-old girl. Preoperative transthoracic echocardiography could not detect the dividing left atrial shelf. In this report, we point out the limitations of transthoracic echocardiography in the diagnosis of atypical cases of so-called cor triatriatum and highlight errors in the scientific literature resulting from the variance in terminology ascribed to congenital division of the left atrium.