The coarctation is due to an inbalance in fetal circulation within the aorta and pulmonary arteries that interferes with normal hemodynamic molding of these arteries. Anatomy The coarctation occurs after the left subclavian which arises from the aortic arch. It begins as an indentation of the posterior wall. The coarctation may be preductal , where the narrowing is proximal to the ductus arteriosus or ligamentum arteriosum. The coarctation may be postductal , where the narrowing is distal to the ductus arteriosus or ligamentum arteriosum.
Collateral circulation connects the proximal and the distal aspects of the vessels over time.
This collateral circulation will develop mainly from the subclavian, scapular, internal thoracic, and intercostal arteries. Collateral circulation is divided into anterior and posterior systems. In the anterior system, the internal mammary arteries and the epigastric arteries join to form collaterals which supply the abdominal wall and the lower extremities. In the posterior system, the parascapular arteries connect with the intercostal arteries to form collaterals which supply the distal aortic compartment and primarily the abdominal viscera. The left subclavian may form collaterals through linkage to the IMA's and intercostals to give blood supply distally.