A persistent left superior vena cava.

Persistent left superior vena cava is the most common form of anomalous venous drainage involving the superior vena cava, and represents persistence of the left horn of the embryonic sinus venosus, which normally involutes during normal development to become the coronary sinus. Almost always, a persistent left superior vena cava enters the right atrium through the orifice of an enlarged coronary sinus. In this case report of a 60-year-old male cadaver, we describe a persistent left superior vena cava and discuss its embryology and clinical significance.