Coronary sinus draining into the left subclavian vein through a persistent left superior vena cava.

A persistent left superior vena cava (PLSVC) is formed by the remains of the oblique vein of the left atrium, which is not completely degenerated during embryonic development. The incidence is approximately 0.3% in the general population. Approximately 80-92% of PLSVCs drain into the right atrium through the coronary sinus. This report describes a rare case of PLSVC in which the coronary sinus (CS) did not open into the right atrium, but rather drained into the left subclavian vein through the PLSVC.