Persistent left superior vena cava with paired azygos veins--report of a case and an attempt at a new classification
Takenoshita, H.
Kaibogaku Zasshi. Journal of Anatomy 61(6): 669-682
1986
ISSN/ISBN: 0022-7722 PMID: 3577654 Document Number: 272579
During the dissection practice of students at Fukushima Medical College in 1985, a persistent left superior vena cava was found along with the right superior vena cava in the cadaver of a 67-year-old Japanese male who died of cerebral arteriosclerosis. The findings obtained were as follows: 1. The left superior vena cava (about 3 mm in diameter) begins at the lower surface about 20 mm to the right of the origin of the left brachiocephalic vein (about 7.6 mm in diameter). The vein descends in front of the aortic arch, forms a coronary sinus (about 10 mm in diameter) and opens into the right atrium. The right superior vena cava (about 12.1 mm in diameter) is formed by the union of the right brachiocephalic vein (about 10.8 mm in diameter) and the left, and opens into the right atrium. 2. The right and left azygos veins have no communicating branch between them, and open into the superior venae cavae on the same sides, i.e., they are paired azygos veins. Embryologically considered, the right brachiocephalic vein and the part of the right superior vena cava between its origin and the point where the right azygos vein opens into it derive from the right anterior cardinal vein. The part of the left brachiocephalic vein between its origin and the origin of the left superior vena cava and the portion of the left superior vena cava between its origin and the point where the left azygos vein opens into it derive from the left anterior cardinal vein. The portions of the superior venae cavae between the points where the azygos veins open into them and the right atrium derive from the common cardinal veins. Also, the section of the left brachiocephalic vein between the origins of the right and left superior venae cavae derives from the inter-anterior cardinal anastomosis. This consideration indicates that the existence or non-existence and inclination of the inter-anterior cardinal anastomosis are responsible for the persistence of the left superior vena cava. Accordingly, the author classified persistent left superior venae cavae the drain into the right atrium into 4 types which fall into 13 subtypes on the basis of the existence or nonexistence, inclination and size of the anastomosis between the right and left superior venae cavae. The present case fits into the IIIc subtype in the author's classification, McCotter's III type and Donadio's II type. Incidentally, the wall of the left superior vena cava is one or two times as thick as the right, although the diameter is one-fourth that of the right. Histologically, the wall of the right superior vena cava is normal, but that of the left has longitudinally arranged smooth muscle fibers sporadically in the tunica media and in abundance in the tunica externa.