Aortic Luminal Contrast Attenuation Varies with Dissection Morphology and is Associated with Need for Intervention.

Objective: Prognostication after acute Type B aortic dissection (aTBAD) may be limited when relying upon static computed tomographic angiography (CTA) images to evaluate a dynamic process. We performed an exploratory study to characterize variations in luminal contrast attenuation on CTA, as a surrogate for blood flow in dissection, and to determine whether the resulting parameters held prognostic value.

Methods: Retrospective, single-institution data for patients with aTBAD were gathered from 1999-2020. Patients with prior dissection repairs were excluded. Dissection morphology was classified by the joint Society for Vascular Surgery / Society of Thoracic Surgeons (SVS/STS) scheme and location/number of fenestrations. Hounsfield unit ratios (HUR) comparing lumina, phases, and aortic zone were calculated. Aortic growth, false lumen thrombosis, and need for intervention were evaluated with logistic regression.

Results: After exclusions, 74 patients were identified (Figure 1). Most fenestrations were in Zone 4/5 (56.5%) and associated with more equilibrated HUR (0.93) compared to dissections without fenestration (0.65, p = 0.04). Intervention occurred in 68.9%. Increased arterial phase false-to-true HUR was strongly associated with eventual need for intervention (odds ratio [OR] 25.3 [95% CI 4.15-188.4], p = 0.001) while increased delayed-to-arterial phase false lumen HUR was associated with decreased intervention (OR 0.49 [95% CI 0.25-0.89], p = 0.02).

Conclusion: In patients with aTBAD, calculated permutations of HUR across lumina and between CTA phases may give insight into blood flow dynamics, which in turn likely impact need for intervention. Future prospective studies of time-resolved CTA are likely to hold significant prognostic value and alter management.