SVC duplication is a relatively common congenital variant diagnosed incidentally. A left-sided SVC is rarely seen in isolation, usually it is accompanied by the right sided SVC - as in this case.

The left IVC more commonly drains to the coronary sinus. Drainage to the left atrium results in a right-to-left shunt which is unlikely to be symptomatic.

It is helpful for clinicians to be aware of the variant prior to pacing lead or central venous line insertion.