Cor triatriatum with single atrium presenting in adulthood.

We present the case of an asymptomatic 21-year-old woman referred because of an abnormal routine electrocardiogram. Transthoracic and transesophageal echocardiography revealed a complete absence of the atrial septum, a common atrium septated posteriorly from the pulmonary venous chamber, a partial atrioventricular canal, a cleft mitral valve and a persistent left superior vena cava draining into an enlarged coronary sinus. These findings were confirmed during surgical correction. Our patient presented with an unusual and fascinating combination of congenital malformations that remained well tolerated and undiscovered into adulthood.