A persistent left superior vena cava is the most common anomaly of the superior caval system. Usually the persistent left superior vena cava is connected with the right atrium via the coronary sinus, resulting in no physiologic derangement : however in 7 to 8 percents of the patietns with a persistent left superior vena cava, the anomalous vessel communicates with the left atrim. In the absence of obstruction to the flow from the left atrium to the left ventricle. this anatomic situation usually results in right to left shunting of varying degress.