Intramural Hematoma of the Aorta
Abstract & Commentary
With Comment by Michael H. Crawford, MD, Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco, Editor, Clinical Cardiology Alert.
Synopsis: There is a 6% incidence of IMH among patients presenting as acute aortic syndromes and it is as lethal as AD, especially in the ascending aorta and, thus, surgery should be considered for patients with type A IMH.
Source: Evangelista A, et al. Circulation. 2005;111: 1063-1070.
The International Registry of Aortic Dissection has enrolled 1010 patients with acute aortic syndromes suspected by clinical presentation and confirmed by imaging, surgical findings, or post-mortem examination. Intramural hematoma (IMH) was defined as an aortic wall hematoma without an intimal flap or tear; the latter being the characteristic of aortic dissection (AD).
IMH was found in 58 (6%) of the patients, who tended to be older (69 vs 62 years, P < .001) and have [more] type B (descending aorta) involvement than AD patients. IMH patients presented with more severe back pain and were less likely to have lower extremity ischemia, aortic regurgitation, and pulse deficits. Although both types of aortic injury usually presented within 4 hours of the onset of pain, IMH patients often took > 24 hours to have the diagnosis made, and required more than 1 imaging test. IMH patients were more likely to have a smaller aortic diameter and a normal ECG. IMH patients were more often treated conservatively, even if the hematoma involved the ascending aorta. Overall, hospital morality was similar (21 vs 24%) and was higher in those with type A involvement for both groups. Finally, among the 51 patients whose initial imaging study showed IMH, a second imaging study showed AD in 8 (16%). The other 7 had initially normal studies and the second study showed IMH. Evangelista and colleagues concluded that there is a 6% incidence of IMH among patients presenting as acute aortic syndromes, and it is as lethal as AD, especially in the ascending aorta. Thus, surgery should be considered for patients with type A IMH.
Comment
The major strength of this study is in the large number of patients seen in multiple centers internationally. The major weakness is that these are all tertiary referral centers, so there is some natural selection taking place at the referring hospital. Thus, the incidence of IMH of 6% may be low because some of the IMH patients may have progressed to AD before arriving at the tertiary center. In fact, the second imaging study showed this progression in 16% of the initially IMH patients. Also, the distribution of IMH is similar to AD; both occur in the descending aorta two-thirds of the time. In addition, despite less cardiac involvement and limb ischemia, the mortality of IMH is similar to AD and is high in ascending aorta cases (39%). Thus, IMH is likely a precursor to AD, which is never seen if progression to AD is rapid.
Patients with type B IMH have a low overall mortality (< 10%), so initial medical therapy seems appropriate. Only 7 patients had aortic arch IMH, and their mortality was zero. So, initial medical therapy would seem reasonable in them also. Medical therapy involves reducing the heart rate to < 60 beats/min and lowering the blood pressure to < 120/80 mm/Hg. Because of the possibility of progression, repeat imaging should be done before discharge, and then at 1, 3, 6, 9, and 12 months post discharge, and yearly thereafter. The best prognostic indicator is aortic size. A normal aortic diameter with IMH predicts regression on medical therapy. Such patients may need less frequent follow-up studies.
There is a 6% incidence of IMH among patients presenting as acute aortic syndromes and it is as lethal as AD, especially in the ascending aorta and, thus, surgery should be considered for patients with type A IMH.
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