Imaging Technique Findings

Computed tomography shows a high attenuation area, usually crecentic or circula, along the aorta wall without intimal flap before contrast injection, which fails to enhance after injection of contrast medium24 (Figure 14.2). Crecentic aortic wall thickening without intimal flap is very easily detected by magnetic resonance imaging; the signal intensity of the thickened aorta is secondary to methemoglobin formation within the hematoma, resulting in increased signal intensity on T1-weighted images in subacute IMH2 (Figure 14.1).

Transesophageal echocardiography is also useful to demonstrate thickening of the aortic wall25 (Figure 14.1), although it offers no signals to identify acute versus chronic hematoma, and a differential diagnosis among other entities that also present thickening of the aorta wall (such as severe atherosclerosis of the intima or aortitis) should be made.

As normal aorta wall thickness is less than 3-4 mm by any imaging modality, aortic wall thickness more than 5 mm with typical clinical symptoms suggesting acute aortic syndrome suffices for diagnosis of intramural hematoma26.

Although studies that compare the diagnostic sensitivity and specificity of imaging techniques do not exist, their diagnostic accuracy does not appear to be so different, and imaging modality selection in the acute phase depends on

Figure 14.1. IMH in descending aorta by four imaging techniques. A. Aortography revealed no abnormalities. B. CT showed an IMH in proximal descending aorta and peraortic hematoma. C. CMR disclosed a hyperintense signal identifying the hematoma. D. TEE showed the same IMH with echolucent areas.

Figure 14.1. IMH in descending aorta by four imaging techniques. A. Aortography revealed no abnormalities. B. CT showed an IMH in proximal descending aorta and peraortic hematoma. C. CMR disclosed a hyperintense signal identifying the hematoma. D. TEE showed the same IMH with echolucent areas.

Figure 14.2. CT reveals a high attenuation signal in ascending aorta (arrows) corresponding to an ascending aorta IMH.

many variables, including clinical situation, physician preference, and availability of experts.

TEE is superior to any other technique for assessing the intima and demonstrating small communications with the Doppler technique (Figure 14.3). One characteristic finding is the presence of echolucent areas or echo-free space within the thickened aorta wall27. By CT with contrast enhancement, it is possible to demonstrate, in selected patients, a small communication through an intimal micro-tear, but this is exceptional in the acute phase. However, the wide field of vision of CT and MRI is important to correctly define the global extension of IMH and periaortic bleeding. A high presence of fluid extravasation, pericardial and pleural effusion, and mediastinal hemorrhage is a frequent finding in IMH12,16,17.

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