Echocardiographic findings in patients with left superior vena cava and dilated coronary sinus.

Three patients with a left superior vena cava draining into a dilated coronary sinus were studied with cardiac catheterization and echocardiography. The diagnosis was confirmed at operation in two patients. A posterior echo-free space was filled with echoes during injection of contrast medium into the left but not the right arm. This echo-free space was localized to the left atrioventricular groove. This technique established the presence of a left superior vena cava communicating with the coronary sinus and excluded pericardial effusion as the source of the posterior echo-free space.