Persistent left superior vena cava (PLSVC) is a rare (~0.5% of the general population) venous anomaly when the left superior cardinal vein fails to degenerate. This can make entering the right heart from the left upper body (e.g., pacing leads, PA catheters, etc.) more challenging as the PLSVC drains directly into the coronary sinus (CS) rather than the right atrium (RA).
During cardiac surgery, if I see an enlarged coronary sinus on transesophageal echocardiography (especially if there is no other reason for the RA pressure to be elevated), I have to consider the presence of a persistent left SVC. Agitated saline contrast injected in a left arm vein will lead to contrast in the CS before the RA. If this is the case, retrograde cardioplegia (given in the CS) won’t be a great option to arrest the heart as the cardioplegia solution will also travel systemically via the PLSVC rather than staying within the coronary venous system.
In this chest x-ray, one can see a dual-chamber pacemaker’s leads traveling through a PLSVC to the heart.
Have you seen PLSVC? Drop me a comment with your experiences and questions!