Background: Acute aortic intramural hematoma (IMH) is an important subgroup of aortic dissection, and controversy surrounds appropriate management.
Methods and results: Patients with acute aortic syndromes in the International Registry of Acute Aortic Dissection (1996-2011) were evaluated to examine differences between patients (based on the initial imaging test) with IMH or classic dissection (AD). Of 2830 patients, 178 had IMH (64 type A [42%], 90 type B [58%], and 24 arch). Patients with IMH were older and presented with similar symptoms, such as severe pain. Patients with type A IMH were less likely to present with aortic regurgitation or pulse deficits and were more likely to have periaortic hematoma and pericardial effusion. Although type A IMH and AD were managed medically infrequently, type B IMH were more frequently treated medically. Overall in-hospital mortality was not statistically different for type A IMH compared to AD (26.6% versus 26.5%; P=0.998); type A IMH managed medically had significant mortality (40.0%), although less than classic AD (61.8%; P=0.195). Patients with type B IMH had a hospital mortality that was less but did not differ significantly (4.4% versus 11.1%; P=0.062) from classic AD. One-year mortality was not significantly different between AD and IMH.
Conclusions: Acute IMH has similar presentation to classic AD but is more frequently complicated with pericardial effusions and periaortic hematoma. Patients with IMH have a mortality that does not differ statistically from those with classic AD. A small subgroup of type A IMH patients are managed medically and have a significant in-hospital mortality.