Dissection of the thoracic aorta

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

Reference:

• (1) Hiratzka LF et al. 2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM guidelines for the diagnosis and management of patients with Thoracic Aortic Disease: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines, American Association for Thoracic Surgery, American College of Radiology, American Stroke Association, Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, Society of Thoracic Surgeons, and Society for Vascular Medicine. Circulation. 2010;121(13):e266-369
• (2) Thrumurthy SG et al. The diagnosis and management of aortic dissection. BMJ. 2011;344:d8290.
• (3) Hebballi R, Swanevelder J. Diagnosis and management of aortic dissection. Contin Educ Anaesth Crit Care Pain (2009) 9 (1): 14
• (4) Baman JR, Malaisrie SC. What Is Aortic Dissection? JAMA. 2023;330(2):198. doi:10.1001/jama.2023.5592
• (5) Curtis SL, Swan L.Aortopathy in pregnancy.Heart Published Online First: 10 February 2022. doi: 10.1136/heartjnl-2021-319828