A case of bilateral superior venae cavae with a closed coronary sinus.

During the routine dissection of a cadaver a left superior vena cava was noticed passing into the coronary sinus. This condition is not uncommon, but further dissection showed that the coronary sinus ended 1 cm. from the wall of the right atrium. Inspection of the right atrium showed no opening for the coronary sinus and the wall between the opening for the inferior vena cava and the tricuspid orifice was smooth. A more complete dissection showed the following details of anatomy. Passing downwards from the proximal end of the left innominate vein was a left superior vena cava. It started about 2 cm. from the junction of the left internal jugular and subclavian veins, and, passing in front of the hilum of the left lung, across the back of the left atrium, it entered the left end of the coronary sinus. At this point the great cardiac vein entered the left superior vena cava from below, and this was the point at which the left superior vena cava was assumed to become the coronary sinus. The length of the left superior vena cava was 11 cm. The left superior intercostal vein and superior hemiazygos vein drained into the left superior vena cava through a common channel 5 cm. long. This common channel opened into the left superior vena cava 1.5 cm. from its beginning. The coronary sinus passed in the usual way from left to right in the posterior atrioventricular groove. Its tributaries from the ventricular wall were normal. As it was followed to the right its diameter increased from 0.7 cm. at its left end to a maximum of 1.5 cm. The diameter then rapidly decreased again until 1 cm. from the wall of the right atrium the coronary sinus ended. Its terminal part was conical in shape. Into the apex of the cone opened two or three small veins, of which one was the middle cardiac vein. No connexion could be found between the closed right extremity of the coronary sinus and the right atrium. The right superior vena cava was present and normal in all respects, as were the inferior vena cava and pulmonary veins. No other congenital abnormality was found in the heart. THE EMBRYOLOGY