What is unusual about the anatomy?On this reformatted CT chest image (maximum intensity projection, MIP), contrast can be seen in veins in the left forearm, as this was the site of the cannula. It then passes into the left axillary vein, then into the left subclavian vein and then into a venous structure in the left side of the mediastinum, draining into a cardiac chamber situated to the right of the left ventricle.
This is a persistent left sided superior vena cava.
- seen in 0.5% of the normal population, 4% with congenital heart disease.
- in 90% there is a small normal right SVC.
- it usually drains into the coronary sinus (as in this case) and then into the right atrium so there is no shunt.
- important to report as will influence site of puncture for major venous line placements
There is a great article explaining the radiology of left sided superior vena cava in more detail on Radiopaedia by Dr Frank Gaillard.