This is how Persistant Left Superior Vena Cava looks in the heart. Notice that the Left Subclavian Vein (vein that returns the blood back to the heart) returns to a large blood vessel which is the Left Superior Vena Cava (this should have disappeared later in life). The Left Superior Vena Cava drains to the Coronary Sinus.

This particular patient had no other abnormalities. She had an innocent heart murmur, but no other symptoms. This is a very unusual cause of an innocent heart murmur.