Aortic intramural haematoma

Aortic intramural haematoma (IMH) is an atypical form of aortic dissection due to haemorrhage into the wall from the vasa vasorum without an intimal tear. It is part of the acute aortic syndrome spectrum.

Typically aortic intramural haematomas are seen in older hypertensive patients. The same condition may also develop as a result of blunt chest trauma with aortic wall injury or a penetrating atherosclerotic ulcer 1-2.

The clinical features of IMH are those of the acute aortic syndromes, namely chest pain radiating to the back and hypertension.

This condition is thought to begin with spontaneous rupture of the vasa vasorum, the blood vessels that penetrate the outer half of the aortic media from the adventitia and arborize within the media to supply the aortic wall 2.

The haematoma propagates along the media layer of the aorta.

Consequently, intramural hematoma weakens the aorta and may progress either to outward rupture of the aortic wall or to inward disruption of the intima, the latter leading to communicating aortic dissection 2.

Classification

Similar to aortic dissections, intramural hematomas are classified according to the Stanford classification system 4:

  • type A: involves the ascending aorta, with or without descending aortic involvement
  • type B: confined to the descending aorta, distal to the origin of the left subclavian artery
CT

Acute intramural haematomas appear as focal, crescentic, high-attenuating (60-70 HU) regions of eccentrically thickened aortic wall on non-contrast CT. Narrow window width is essential for identifying subtle lesions. Intimal calcification may be displaced inwards, best appreciated on non contrast phase.

The lesions exhibit low attenuation in relation to the aortic lumen on post-contrast CT and can be far more subtle, hence a non contrast phase before CTA is often used in an acute aortic syndrome protocol. Unlike aortic dissection, no intimal flap is present on the CTA.

Other modalities

Echocardiography and MRI may also detect the abnormality but conventional angiography will not.

If IMH involves the ascending aorta (Stanford A), treatment is surgical to prevent rupture or progression to a classic aortic dissection.

Conservative management is indicated for aortic IMH of the descending aorta (Stanford B).

Untreated, IMH can be life-threatening as it can lead to:

  • aortic rupture
  • aortic dissection
  • aortic aneurysm

The main differential diagnoses are:

  • thrombosed false lumen in classic aortic dissection: typically spirals longitudinally around the aorta whereas an intramural haematoma usually maintains a constant circumferential relationship with the aortic wall
  • aortitis: typically shows concentric uniform thickening of the aortic wall with or without peri-aortic inflammatory stranding, whereas an intramural haematoma is often eccentric in configuration
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Article Information

rID: 919
Systems: Vascular, Chest
Section: Pathology
Synonyms or Alternate Spellings:
  • Aortic intramural hematoma
  • Aortic intramural hematoma (IMH)
  • Aortic intramural haematomas
  • Aortic intramural hematomas

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