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Coarctation of the aorta

Dr Henry Knipe and Dr Frank Gaillard et al.

Coarctation of the aorta refers to a narrowing of the aortic lumen. It can be primarily divided into two types:

  1. infantile (pre-ductal) form 
  2. adult (juxta-ductal, post-ductal or middle aortic) form 

Infantile coarctation is characterised by diffuse hypoplasia or narrowing of the aorta from just distal to brachiocephalic artery to the level of ductus arteriosus, typically with a more discrete area of constriction just proximal to the ductus but distal to the origin of the left subclavian artery. Therefore the blood supply to the descending aorta is via the patent ductus arteriosus

Adult coarctation in contrast is characterised by a short segment abrupt stenosis of the post-ductal aorta. It is due to thickening of the aortic media and typically occurs just distal to the ligamentum arteriosum (remnant of the ductus arteriosus).  

Epidemiology

Coarctations account for between 5-8% of all congenital heart defects. They are more frequent in males, M:F ratio of ~2-3:1.

Pathology

Associations

As is the case with many congenital abnormalities, coarctation of the aorta is associated with other anomalies. 

Radiographic features

Plain film: chest radiograph
  • figure of 3 sign: contour abnormality of the aorta
  • inferior rib notching: Roesler sign
    • secondary to dilated intercostal collateral vessels which form as a way to bypass the coarctation and supply the descending aorta
    • the dilated and tortuous vessels erode the inferior margins of the ribs, resulting in notching
    • seen only in long standing cases, and therefore not seen in infancy
    • seen in 70% of cases presenting in older children or adults
    • if the coarctation is distal to either subclavian artery, then increased flow occurs through the subclavian artery, forming a collateral pathway via the internal thoracic artery, anterior intercostal artery, posterior intercostal artery and then into the descending thoracic aorta
    • usually the 4th to 8th ribs are involved; occasionally involves the 3rd to 9th ribs
    • as the 1st and 2nd posterior intercostal arteries arise from the costocervical trunk (a branch of the subclavian artery) and do not communicate with the aorta, these are not involved in collateral formation, and the 1st and 2nd ribs do not become notched
    • if bilateral rib notching: the coarctation must be distal to the origin of both subclavian arteries, to enable bilateral collaterals to form
    • if unilateral right rib notching, then the coarctation lies distal to the brachiocephalic trunk, but proximal to the origin of the left subclavian artery. Collaterals cannot form on the left, as the left subclavian is distal to the coarctation.
    • if unilateral left rib notching, then this suggests an associated aberrant right subclavian artery arising after the coarctation. The coarctation is distal to the origin of the left subclavian artery, therefore collaterals form on the left. Collaterals cannot form on the right, as the aberrant right subclavian artery arises after the coarctation
  • may also show evidence of left ventricular hypertrophy
Antenatal ultrasound

Useful in assessing for infantile coarctations. The suprasternal notch-long axis views are particularly considered helpful. The fetal right ventricle can be appear enlarged in severe coarctations although this alone is not a specific feature. Occasionally an aortic arch view may directly show a narrowing.

Angiography: CTA/MRA/DSA

All modalities are capable of delineating the coarctation as well as collateral vessels, most common collateral pathway being subclavian artery to internal mammary artery to intercostal arteries (resulting in inferior rib notching) to post-coarctation part of descending thoracic aorta.

Treatment and prognosis

Urgency of treatment depends on the presence of congestive cardiac failure. This is usually the case in severe coarctations found in infancy. In less severe cases, elective treatment when the child is older (typically ~2 years of age) is preferred 3

Treatment can be either primary surgical repair with excision of the coarctation and end-to-end anastomosis, or balloon angioplasty.

Complications

Differential diagnosis


Related articles

Congenital heart disease

There is more than one way to present the variety of congenital heart diseases. Whichever way they are categorised, it is helpful to have a working understanding of normal and fetal circulation, as well as an understanding of the segmental approach to imaging in congenital heart disease.

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