dissection of thoracic aorta aneurysm

Last edited 02/2022 and last reviewed 03/2022

Aortic dissection is a condition caused by disruption of the media layer of the aorta with bleeding within and along the wall of the aorta which separates the layers of aorta (1)  

  • an intimal disruption is seen in 90% of cases resulting in tracking of the blood in a dissection plane within the media creating a false lumen in the aorta which may spread in an antegrade or retrograde manner within the vessel
  • this false lumen may rupture through the adventitia or back through the intima into the aortic lumen creating a septum, or “flap,” between the 2 lumens
  • the false lumen may thrombose over time (1)

According to the time between the onset of symptoms and diagnosis aortic dissection can be:

  • acute – when the diagnosis is made within 14 days of onset
  • chronic – diagnosis made 14 days after the onset (2)

Aortic dissections are seen

  • along the greater curvature of the aorta (usually within 10 cm of the aortic valve) in majority of dissections (3)
  • in the descending thoracic aorta immediately distal to the origin of the left subclavian artery - the next most commonest site (3)

Aortic dissection is often used synonymously with dissecting aneurysm. This is not strictly correct as dissection may occur in the absence of a pre-existing aneurysm.

Aortic dissection in pregnancy (4)

  • is one of the most common causes of death in pregnancy
  • most cases are caused by hereditary thoracic aortopathy (HTA), and women are often unaware they are at risk
  • dissection is most common post partum