Abstract
Cor triloculare biatriatum is a rare form of congenital heart disease that needs to be considered in the differential diagnosis of the important group of patients with cyanotic congenital heart disease with pulmonary hypertension. The clinical and pathologic features of an example of this disease are reported and discussed in a review of previously reported cases. The small pulmonary blood vessels showed some features of hypertensive pulmonary vascular disease and evidence of an increased bronchial arterial collateral circulation to the lung. An interpretation of these histologic changes relating them to the abnormal pulmonary physiology in cor triloculare biatriatum is suggested.