Clinical importance of minimal enhancement of type B intramural hematoma of the aorta on computed tomography imaging.

OBJECTIVE: To investigate the instability, morphology, natural course, and prognostic value of enhancement of the thrombosed false lumen on contrast-enhanced computed tomography (CT) scans in patients with type B intramural hematoma of the aorta (IMH). METHODS: A total of 65 patients (42 men; mean age, 75 years) with type B IMH were evaluated retrospectively. On initial CT scans, attenuation of the false lumen (AFL) was determined before enhancement and in the early and delayed phases of contrast enhancement. Then enhancement of the false lumen (EFL) was calculated (AFL in the delayed image - AFL in the precontrast image). The Cox proportional hazards model was employed to estimate the risk of IMH-related events, including death or surgical repair. RESULTS: The mean AFL for precontrast CT, arterial phase enhanced CT, and delayed phase enhanced CT was 56.3 ± 10.5, 59.9 ± 10.8, and 63.7 ± 11.1 Hounsfield units, respectively, whereas the mean EFL was 7.4 ± 9.0 Hounsfield units. EFL was the only independent predictor of IMH-related events (n = 23; hazard ratio, 1.008; 95% confidence interval, 1.03-1.15; P = .0044) and IMH-related death/surgical repair (n = 10; hazard ratio, 1.111; 95% confidence interval, 1.017-1.213; P = .0197). CONCLUSIONS: In patients with IMH, EFL is the most powerful predictor of IMH-related events, as well as IMH-related death or surgical repair.