Coarctation of aorta

Question 1

Definition

Answer 1

Narrowing of aorta at or just distal to the insertion of the ductus arteriosus, resulting in stronger PERFUSION to the upper body compared to the lower body.

Question 2

Pathophysiology of adult form (30% of cases)

Answer 2

• Narrowing of the aorta just distal to the closed ductus arteriosus (ligamentum arteriosum) results in increased blood flow through the aortic arch branches (brachiocephalic trunk, left common carotid, left subclavian) to the head & upper body & decreased perfusion to the lower body.
  
  • Stronger perfusion to the upper body results in hypertension in the upper limbs & discrepant pulses- radial pulse is felt BEFORE femoral pulse. Femoral pulse will be weak/absent.
  • Increased cerebral blood flow through carotid & vertebral arteries → increased risk of Berry aneurysms (dilation in weakened artery walls, most common at bifurcation points of Circle of Willis).
  • Decreased renal perfusion results in activation of RAAS & systemic secondary hypertension.

Question 3

What is the CXR finding in coarctation of aorta & why?

Answer 3

Notched ribs 3-12 on CXR due to dilated posterior intercostal arteries (these run in a neurovascular bundle in costal grooves: vein, artery, nerve).

• Anterior intercostal arteries branch from the internal thoracic artery which branches from the subclavian artery (branch BEFORE the narrowing). Posterior intercostal arteries supplying ribs 3-12 branch off the thoracic aorta DISTAL to the narrowing.
• Normally, the blood flow through the anterior & posterior intercostal arteries is equal with anastomoses between them.
  In COT: During systole, there is increased pressure in the anterior intercostal arteries & decreased pressure in the posterior intercostal arteries so blood flows from the anterior → posterior intercostal arteries resulting in dilation of the posterior intercostal arteries (in the costal grooves) which rub against the ribs, causing RIB NOTCHING of ribs 3-12.

Question 4

Signs & symptoms

Answer 4

Signs

• Weak/absent femoral pulse (due to decreased perfusion to lower body distal to narrowing)
• Discrepant blood pressure- hypertension in upper limbs compared to lower limbs & delay between radial & femoral pulses.
• Scapular bruits due to HTN in collateral

Question 5

Investigations

Answer 5

1st line:

• CXR- may show posterior rib notching due dilation of posterior intercostal arteries (these rub against ribs in the costal grooves)
• CT angiogram- useful adjunct with ECHO, shows anatomy of narrowing as it can be in variable positions.

Question 6

Management

Answer 6

Surgical repair OR percutaneous angioplasty with stenting (balloon catheter is inflated & stent implanted)