For the last decade aortic intramural hematoma (AIH), a variant form of classic aortic dissection (AD), has emerged as an increasingly recognized and potentially fatal entity of acute aortic syndrome (AAS). The successful clinical introduction of noninvasive imaging modalities for aortic diseases, including transesophageal echocardiography (TEE), has contributed to early differential diagnosis of AIH and investigation of its natural course or remodeling process after the initial event.
AIH, which is characterized by circular or crescentic aortic wall thickening without an intimal flap or tear, is easily differentiated from classic AD. Other findings suggestive of AIH are smooth contour of the aortic lumen, increased density of aortic wall thickening before contrast injection, and demonstration of an 'echo-lucent area' or 'echo-free space' within the thickened aortic wall. It is widely accepted that AIH is not just a precursor of AD but has diverse remodeling processes, and, compared to classic AD, has a more favorable clinical course including complete resorption with medical treatment, reported even in type A pathology. Further study has demonstrated that two important predictors for the development of AD or mortality are aortic diameter and hematoma thickness. Thus, noninvasive imaging modalities are useful not only for diagnosis but also for risk stratification and treatment strategy selection. Although a consensus regarding optimal management strategies, especially for type A AIH, has not been established, this is in part due to our incomplete understanding of AIH. With more information of this interesting disease entity, the role of TEE and other noninvasive imaging modalities is expected to be reestablished in the near future.