Cor triatiratum dexter: a rare cause of isolated right atrial enlargement.

Cor triatriatum sinistrum (division of the left atrium) is a recognized clinical and surgical entity. Division of the right atrium, also known as cor triatriatum dexter, is an extremely rare congenital abnormality in which persistence of the right valve of the embryonic systemic sinus venosus divides the right atrium into two chambers. Typically, the right atrial partition is due to exaggerated fetal eustachian and thebesian valves, which together form an incomplete septum across the lower part of the atrium. This septum may range from a reticulum to a substantial sheet of tissue. Cor triatriatum dexter can be diagnosed at any age, especially if it is incidentally discovered. Usually, this anomaly is recorded at necropsy. This report describes the case of a divided right atrium evaluated for nonspecific symptoms and unexplained cardiomegaly with right atrial enlargement.