The presence of a left SVC is a result of persistence of the embryological left anterior cardinal vein.
A left superior vena cava occurs in approximately 0.5% of the population and occurs in 5-10% of individuals with congenital heart defects.
When the left superior vena cava persists drainage occurs via the coronary sinus into the left atrium.
With the persistence of the left SVC the right SVC may be absent as may the left brachiocephalic vein.
Dilated neck veins usually noted and swelling of the arms, face neck, and supraclavicular area may be present.
Collateral veins may be present over the upper chest as a result of the gradual occlusion of the superior vena cava.
Chest x-ray may be normal or show a right suprahilar mass or medicinal widening.