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.