Coarctation of the aorta is aortic narrowing that typically occurs proximal to the ductus arteriosus (can be termed “preductal” or “postductal” based on location of the stenosis
in relation to the ductus arteriosus), resulting in increased LV afterload. Coarctation can be symptomatic early (infantile form) or later in life (adult form), depending on severity of stenosis and if there is a patent ductus arteriosus (PDA) at birth:
- Infantile form: Aortic narrowing proximal to a PDA, which can lead to cyanosis of the lower half of the body due to right-to-left shunting via the PDA to vessels below the aortic arch. Note that the upper half of the body is supplied by branches of the aortic arch, which are unaffected by the distal right-to-left shunt.
- Adult form: Aortic narrowing distal to the aortic arch without PDA.
Presents later in life, with hypertension in upper extremities (supplied by the
branches of the aortic arch) and hypotension in lower extremities from decreased
blood flow across the coarctation and absence of PDA. As a result, collateral circulation
usually develops to route blood from the aorta to the lower extremities (from
the proximal aorta via the subclavian artery, to the internal thoracic artery, to the
superior epigastric artery, to the inferior epigastric artery, to the external iliac artery).
Increased blood flow to the intercostal arteries causes them to dilate and eventually
erode into ribs. This process results in the characteristic “rib notching” associated
with coarctation of the aorta.