Advancing cor triatriatum in Fontan circulation.

A 14-year-old female with mitral atresia, double outlet right ventricle, l-malposition of the great arteries, pulmonary valvular stenosis, bilateral superior vena cavae, and juxtaposed right atrial appendage had undergone a staged Fontan completion at 22 months of age. Ten years later, transthoracic echocardiography detected blood flow acceleration in the left atrium and scheduled follow-up cardiac catheterization revealed a 3.3 mm Hg pressure gradient between the common pulmonary venous chamber and left atrium, confirming cor triatriatum. An abnormal septum in the left atrium was surgically resected through a left-side right atriotomy. Postoperative echocardiography showed no accelerated blood flow in the left atrium.