Where does a persistent left superior vena cava typically drain?

• A. Into the coronary sinus or right atrium.
• B. Into the left atrium.
• C. Into the portal vein.
• D. Into the pulmonary artery.

Answer: (A)

A persistent left superior vena cava most often drains into the coronary sinus, which then returns blood to the right atrium. This occurs because the left-sided cardinal vein fails to regress during development, creating a venous channel that courses to the heart via the coronary sinus. In fetal echocardiography, this is usually seen as a separate venous structure on the left side and may enlarge the coronary sinus as it handles the venous return to the right heart.

If the left SVC were to drain into the left atrium, that would create a right-to-left shunt and potential systemic desaturation, which is not the typical scenario. Draining into the portal vein or pulmonary artery is not characteristic of this anomaly. Therefore, the most common and expected drainage pathway is into the coronary sinus, leading to the right atrium.