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- AAS, acute aortic syndrome
- CT, computed tomography
- IMH, intramural haematoma
- MRI, magnetic resonance imaging
- TOE, transoesophageal echocardiography
Aortic intramural haematoma (IMH), a variant form of classic aortic dissection, has been accepted as an increasingly recognised and potentially fatal entity of acute aortic syndrome (AAS).1 In classic aortic dissection, flow communication occurs through a demonstrable primary intimal tear and blood flow propagation creates a so called “double channel aorta” with a true and false lumen. In IMH, it is believed that haemorrhage occurs within the aortic wall in the absence of initial intimal disruption. Thus, conventional aortography, which is useful for detection of intimal flap or double channel aorta in classic aortic dissection, failed to identify this disease entity and antemortem diagnosis of IMH was difficult.2 With recent advances and successful clinical introduction of various non-invasive imaging modalities for aortic pathology, such as contrast enhanced x ray computed tomography (CT), magnetic resonance imaging (MRI), and transoesophageal echocardiography (TOE), the clinical significance of IMH can be truly estimated. In this presentation, I would like to focus on the characteristic imaging features of IMH by these modalities and difficult scenarios for diagnosis.
DIAGNOSTIC CRITERIA
Non-invasive radiological techniques, CT and MRI, were first used for diagnosis of IMH—“aortic dissection without intimal rupture”.3 In CT, demonstration of continuous, usually crescentic, high attenuation areas along the aortic wall without intimal flap is characteristic before contrast injection (fig 1A⇓), which fail to be enhanced after injection of contrast medium (fig 1B⇓). Crescentic aortic wall thickening without intimal flap or tear is also very easily detected by MRI; the signal intensity of the thickened aortic wall might be variable, dependent on the amount of methaemoglobin formation within the haematoma (fig 1C⇓). TOE is also useful to demonstrate circumferential or crescentic aortic wall thickening without intimal tear4; displacement of intimal calcification caused by accumulation of blood within the aortic media …