It was thought that expansion of the lung and cardiac atriums was required for obliteration of the anterior cardinal vein
(PCV: posterior cardinal vein
, DA: dorsal aorta, and DLAV: dorsal longitudinal anastomotic vessel).
Its incidence is 0.3-0.5% in general population and 3-10% in patients having congenital heart disease.3 The failure of regression of left cardinal vein
during embryological development4 is the main etiology behind the defect.
First the posterior cardinal vein
appears, but regresses completely except the distal part which forms the iliac bifurcation.
Cranially, the azygos lines join the persistent cranial ends of the postcardinal veins which form the root of the azygos on the right and together with the distal part of the anterior cardinal vein
on the left, form the left superior intercostal vein (Mahato, 2009).
They result from the failure of regression of the right supra-cardinal vein and left anterior cardinal vein
, respectively (1-4).
The lowest part of right posterior cardinal vein
The left superior intercostal vein and accessory hemiazygos vein are derived from left posterior cardinal vein
and this vein simultaneously forms upper part of azygos vein.
The cephalic parts of anterior cardinal veins
form the internal jugular veins and the caudal part of the right anterior cardinal vein
develop into the normal right superior vena cava (RSVC).