BACKGROUND: It has been reported that early surgery should be required for 
patients with type A aortic intramural hematoma (IMH) because it tends to 
develop classic aortic dissection or rupture. However, the anatomic features of 
type A IMH that develops dissection or rupture are unknown. The purpose of this 
study was to investigate the predictors of progression or regression of type A 
IMH by computed tomography (CT).
METHODS AND RESULTS: Twenty-two consecutive patients with type A IMH were 
studied by serial CT images. Aortic diameter and aortic wall thickness of the 
ascending aorta were estimated in CT images at 3 levels on admission and at 
follow-up (mean 37 days). We defined patients who showed increased maximum 
aortic wall thickness in the follow-up CT (n=9) or died of rupture (n=1) as the 
progression group (n=10). The other 12 patients, who all showed decreased 
maximum wall thickness, were categorized as the regression group. In the 
progression group, the maximum aortic diameter in the initial CT was 
significantly greater than that in the regression group (55+/-6 vs 47+/-3 mm, 
P=0.001). A Cox regression analysis revealed that the maximum aortic diameter 
was the strongest predictor for progression of type A IMH. We considered the 
optimal cutoff value to be 50 mm for the maximum aortic diameter to predict 
progression (positive predictive value 83%, negative predictive value 100%).
CONCLUSIONS: Maximum aortic diameter estimated by the initial CT images is 
predictive for progression of type A IMH.