The coarctaion may be :Preductal - where is narrowing is proximal to the ductus arteriosus or ligamentum arteriosum. or Postductal - where the narrowing is distal to the ductus arteriosus or ligamentum arterosuin.Collateral circulation connects the proximal and the distal aspects of the vessels over time. This collateral circulation will develop mainly from the : -Subclavian,                   u Internal thoracic                                                             u Intercostal arteriesu Axillary,                         u Superior and inferior epigastric andFollowing collateral connections may be seen :In the anterior thoracic wall, the internal mammary arteries (arising from subclavian arteries) and the epigastric arteries join to form collaterals which supply the abdominal wall and the lower extremities. Internal mammary artery gives rise to anterior intercostal arteries which forms anastomoses with the posterior intercostal (post intercostals arise from descending aorta). Superior epigastric artery is terminal branch of internal mammary artery and forms anastomoses with inferior epigastric artery which arises from external iliac artery. Musculophrenic artery is terminal branch of internal mammary artery and forms anastomoses with inferior plirenic and post intercostals. The Para scapular arteries (arising from subclavian artery and axillary arteries) connect with the posterior intercostal arteries to form collaterals which supply the distal aortic compartment. The suprascapular artery from the subclavian; and the thoracoacromial, lateral thoracic and subscapular arteries from the axillary; and the first and second posterior intercostal arteries from the costocervical trunk anastomose with other posterior intercostal arteries. One route of collateral formation can be subclavian artery - vertebral artery-spinal arteries - post intercostals and lumbar artery - aorta.