Ligament of the left vena cava

Overview
Between the left pulmonary artery and subjacent pulmonary vein is a triangular fold of the serous pericardium; it is known as the ligament of the left vena cava (vestigial fold of Marshall).

It is formed by the duplicature of the serous layer over the remnant of the lower part of the left superior vena cava (duct of Cuvier), which becomes obliterated during fetal life, and remains as a fibrous band stretching from the highest left intercostal vein to the left atrium, where it is continuous with a small vein, the vein of the left atrium (oblique vein of Marshall), which opens into the coronary sinus.