Coarctation of the aorta

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 

An infantile coarctation is characterised by diffuse hypoplasia or narrowing of the aorta from just distal to brachiocephalic artery to 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. 

An 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 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 cases with many congenital abnormalities, coarctation of the aorta is associated with other anomalies. 

• cardiac : coarctations are frequently associated with other congenital heart defects and conditions which include.
  • bicuspid aortic valve : most common associated defect and seen in 75 - 80 %
  • ventricular septal defect (VSD)
  • cyanotic congenital lesions including
    • truncus arteriosus
    • transposition of the great arteries (TGA), especially with a sub-pulmonic VSD and overriding pulmonary artery (Taussig-Bing)
  • mitral valve defects including
    • hypoplastic mitral valve
    • parachute mitral valve
    • abnormal papillary muscles
• there can also be non cardiac associations such as
  • intracranial berry aneurysms
  • spinal scoliosis
• recognised syndromic associations include
  • cardiac
    • Shone syndrome
  • wider syndromic
    • PHACE syndrome
    • Turner syndrome : a coarctation can be seen in 15 - 20 % of those with Turner syndrome

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
  • seen only in long standing cases, and therefore not seen in infancy
  • seen in 70% of cases presenting in older children or adults
  • if unilaterally seen on the left, then this suggests an associated aberrant subclavian artery arising after the coarctation
  • if unilaterally seen on the right then the origin of the left subclavian artery is involved in the coarctation
  • most often involves 4^th - 8^th ribs
  • occasionally involves 3^rd and 9^th ribs
  • does not involve 1^st and 2^nd ribs ( the associated arteries are branches of the costocervical trunk, and thus proximal to 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 a 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. 

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

• neonatal heart failure
• subarachnoid haemorrhage from ruptured berry aneurysm
• aortic dissection
• infective endocarditis : in the context of an added infective insult
• mycotic aneurysm : in the context of an added infective insult

Differential diagnosis

• pseudo-coarctation on the aorta : elongation, narrowing or kinking with no pressure gradient or collateral formation : no rib notching
• chronic large vessel arteritis : e.g chronic phase of Takayasu arteritis