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, namesly 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.
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
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.
Echocardiography and MRI may also detect the abnormality but conventional angiography will not.
Treatment and prognosis
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
- acute aortic syndrome
- thoracic aortic aneurysm
- abdominal aortic aneurysm
- endovascular aneurysm repair (EVAR)
- reporting tips for aortic aneurysms
- aortic coarctation
- aortic pseudocoarctation
- cervical aortic arch
- interrupted aortic arch
- transposition of the great arteries
- variant anatomy of the aortic arch
- traumatic aortic injuries
- 1. Sebastià C, Pallisa E, Quiroga S et-al. Aortic dissection: diagnosis and follow-up with helical CT. Radiographics. 19 (1): 45-60. Radiographics (full text) - Pubmed citation
- 2. Macura KJ, Corl FM, Fishman EK et-al. Pathogenesis in acute aortic syndromes: aortic dissection, intramural hematoma, and penetrating atherosclerotic aortic ulcer. AJR Am J Roentgenol. 2003;181 (2): 309-16. AJR Am J Roentgenol (full text) - Pubmed citation
- 3. Song JK. Diagnosis of aortic intramural haematoma. Heart. 2004;90 (4): 368-71. Free text at pubmed - Pubmed citation
- 4. Chao CP, Walker TG, Kalva SP. Natural history and CT appearances of aortic intramural hematoma. Radiographics. 2009;29 (3): 791-804. doi:10.1148/rg.293085122 - Pubmed citation
- 5. Holden A. The value of narrow CT window settings in the recognition of subtle acute aortic intramural haematoma. Australas Radiol. 2000;44 (1): 128-9. Pubmed citation