Atrial septal defect with cyanosis without pulmonary hypertension or anomalous systemic venous drainage to the left atrium.

A case of a 29-year-old patient with cyanosis due to a right-to-left shunt is reported. This patient presented an atrial septal defect within the oval fossa and an anomalous left superior caval vein. The direction of this shunt is explained by the anatomical relationship between the oval fossa and the dilated coronary sinus, draining venous blood into the left atrium across the atrial septal defect. Cyanosis disappeared after surgical correction of the defect.