Left superior vena cava: cross-sectional imaging overview.

Persistent left-sided superior vena cava (PLSVC) is the commonest systemic venous anomaly in the thorax with a reported prevalence of up to 0.5% in otherwise normal population and up to 10% in patients with congenital heart disease (CHD). In the absence of associated CHD, it is usually asymptomatic, discovered incidentally. It may complicate catheter or pacemaker lead placement. PLSVC typically drains into the right atrium through the coronary sinus. In children with CHD, the presence of a PLSVC may affect the choice of certain surgical procedures. PLSVC is significantly more common in association with situs ambiguous than with situs solitus or inversus, up to 60-70%. In patients with situs ambiguous, the drainage of LSVC is variable, more commonly directly into the atria rather than through the coronary sinus (CS). Rarely, there is a PLSVC draining into the CS with absent right SVC. PLSVC draining into the right atrium via the CS will not usually cause blood shunting between the right and the left sides. However, shunting occurs when PLSVC is associated with unroofed CS, or when it directly drains into the left atrium. With an increased use of CT and MRI for chest and cardiac imaging, PLSVC is being more encountered by radiologists than before. In this article, we will discuss the embryology of PLSVC, its anatomic course and drainage pathways, as well as its clinical relevance and relation to congenital heart disease and viscero-atrial situs.