Aortic intramural hematoma (IMH) is an atypical form of aortic dissection due to hemorrhage into the wall from the vasa vasorum without an intimal tear. It is part of the acute aortic syndrome spectrum.
Typically aortic intramural hematomas 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 hematoma propagates along the medial 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 a communicating aortic dissection 2.
Similar to aortic dissections, intramural hematomas are classified according to the Stanford classification 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
The DeBakey classification can also be used 5.
Acute intramural hematomas appear as focal, crescentic, high-attenuating (60-70 HU) regions of eccentrically thickened aortic wall on non-contrast CT (high-attenuation crescent sign). Narrow window width is essential for identifying subtle lesions 6. Intimal calcification may be displaced inwards, best appreciated on the 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 done in an acute aortic syndrome protocol. Unlike aortic dissection, no intimal flap is present on the CTA.
An intramural hematoma (IMH) may be readily visualized with transesophageal echocardiography, which offers superior visualization of the aorta than is usually available via transthoracic examinations. Defining features include 10:
- crescentic thickening of the aortic wall
- normal aortic wall thickness < 3 mm
- wall thickness must exceed 7 mm to diagnose IMH
- wall demonstrates mixed echogenicity
- predominantly echodense with scattered internal echolucencies
- no internal flow detectable
- lack of an intimal (dissection) flap
- the luminal surface in IMH tends to be smooth and continuous
MRI may also detect the abnormality but conventional angiography will not.
Treatment and prognosis
If an intramural hematoma involves the ascending aorta (Stanford A), treatment is surgical to prevent rupture and progression to a classic aortic dissection.
Conservative management is indicated for an intramural hematoma of the descending aorta (Stanford B).
- 77% of intramural hematomas regress at 3 years
- survival of >90% at 5 years 7
Untreated, an intramural hematoma can be life-threatening as it can lead to:
The main differential diagnoses are:
- thrombosed false lumen in classic aortic dissection: typically spirals longitudinally around the aorta whereas an intramural hematoma 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 hematoma is often eccentric in configuration
- 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. Vilacosta I, San Román JA, Ferreirós J, Aragoncillo P, Méndez R, Castillo JA, Rollán MJ, Batlle E, Peral V, Sánchez-Harguindey L. Natural history and serial morphology of aortic intramural hematoma: a novel variant of aortic dissection. American heart journal. 1997 Sep 30;134(3):495-507.
- 6. 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
- 7. Rathore, A. Current Concepts in Vascular Therapies, 2017 http://conceptsinvasculartherapies.com/pdf/2017/FridaySessions/FriS21130-PenetratingAtheroscleroticUlcersoftheAorta-Rathore.pdf
- 8. Ihab B. Alomari, Yasmin S. Hamirani, George Madera, Cyril Tabe, Nila Akhtar, Veena Raizada. Aortic Intramural Hematoma and Its Complications. (2014) Circulation. 129 (6): 711. doi:10.1161/CIRCULATIONAHA.113.001809 - Pubmed
- 9. Gutschow SE, Walker CM, Martínez-Jiménez S, Rosado-de-Christenson ML, Stowell J, Kunin JR. Emerging Concepts in Intramural Hematoma Imaging. (2016) Radiographics : a review publication of the Radiological Society of North America, Inc. 36 (3): 660-74. doi:10.1148/rg.2016150094 - Pubmed
- 10. Ivascu NS, Skubas NJ. Aortic intramural hematoma: echocardiographic characteristics. (2012) Anesthesia and analgesia. 114 (2): 286-8. doi:10.1213/ANE.0b013e318239c2cb - Pubmed
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