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Dissection of the thoracic aorta

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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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.

Risk factors (4)

  • most important risk factor is hypertension - which causes increased stress on the aortic wall
  • other risk factors include:
    • atherosclerosis of the aorta
    • preexisting aortic aneurysm
    • bicuspid aortic valve
    • cocaine use
    • traumatic injury to the chest
    • certain genetic disorders (such as Marfan syndrome and Turner syndrome);
    • certain connective tissue disorders (such as Ehlers-Danlos syndrome)

Aortic dissection in pregnancy (5)

  • 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


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