Ligament of left superior vena cava

The ligament of the left superior vena cava (Ligament of Marshall) is the embryological remnant that forms when the left anterior cardinal vein normally regresses during fetal development. In typical cardiac development, this vein obliterates and becomes a fibrous ligamentous structure rather than persisting as a functional vessel.

When the left anterior cardinal vein fails to regress normally, it persists as a left superior vena cava (LSVC), which is the most common congenital anomaly of the thoracic venous system, occurring in approximately 0.3-0.5% of the general population and up to 5-10% of patients with congenital heart disease. The persistent LSVC typically drains into the right atrium via a dilated coronary sinus, though in approximately 8% of cases it may drain directly into the left atrium.

The ligament of left superior vena (ligament of Marshall) is contained in a left lateral ridge formed by the coalition of the left superior pulmonary vein and left atrial appendage, which results in a lateral fold of left atrial wall tissue. The ridge contains the ligament of Marshall, autonomic nerve bundle, and small atrial or sinoatrial node artery. This ridge is called "coumadin" or "warfarin" ridge since it was commonly misdiagnosed as a thrombus, which resulted in unnecessary anticoagulation.