Persistent left superior vena cava: case reports and clinical implications.

We report four cases of persistent left superior vena cava (LSVC) incidentally recognized during device implantation. Persistent LSVC is the commonest venous anomaly of the thorax and drains into the right atrium via the coronary sinus. Persistent LSVC demonstrates several congenital variations including variable communication with right-sided superior vena cava (SVC), absence of right-sided SVC, drainage into the left atrium creating a right to left shunt, and association with other congenital anomalies of the heart and great vessels. Abnormal persistent fetal dispersion of specialized pacemaker and conduction tissue, which occurs in some individuals with persistent LSVC, may provide an arrhythmogenic substrate. In this article we discuss embryology, diagnostic approaches, clinical features, technical difficulties in accessing the right ventricle, and a review of literature related to persistent LSVC.