Persistent Left Superior Vena Cava with Absent Right Superior Vena Cava.

Persistent left superior vena cava (PLSVC) is the most common congenital abnormality of the thoracic systemic venous drainage; in fact, cardiology fellows in training are often quizzed on this when a dilated coronary sinus is noted on an echocardiogram. However, its association with an absent right superior vena cava (RSVC) and how to diagnose this combined condition is less commonly known. We present two cases of PLSVC with an absent RSVC, describe how to recognize and confirm this diagnosis, and discuss its clinical relevance.