Radiographic phenotyping of healthy and diseased aortas

BACKGROUND: Ascending aortic diameter guides intervention for thoracic aneurysms. Many patients with acute type A aortic dissection (ATAAD) present with ascending aortic diameters below 5.5 cm, rendering diameter an insufficient risk discriminator. This study evaluated computed tomography angiography (CTA) morphology to identify predissection radiographic features associated with ATAAD. METHODS: Control (n = 50, CTA for non-aortic indications), aneurysm (n = 61, thoracic ascending aorta [TAA] ≥ 4.5 cm), and predissection (n = 13, CTA within 3 years before dissection) groups were studied. Scans were interpreted by thoracic radiologists using predefined measurements. RESULTS: Age and sex distribution differed overall among groups (P < 0.001 and P = 0.010, respectively). The aneurysm group was older than controls, but the age difference from the predissection group was not significant (P = 0.084). Maximum TAA diameter (MaxD) was 3.11 ± 0.30, 4.96 ± 0.52, and 3.89 ± 0.60 cm in control, aneurysm, and predissection groups respectively; all predissection MaxD values were below 5.5 cm (maximum, 4.9 cm). Ascending aortic length (AAL) was elevated in both disease groups (aneurysm group, 9.03 ± 1.08 cm; predissection group, 10.73 ± 1.41 cm; P < 0.001 vs. control group, 6.38 ± 0.75 cm). The AAL/MaxD ratio differed significantly between every pair of groups (control group, 2.06 ± 0.22; aneurysm group, 1.83 ± 0.21; predissection group, 2.80 ± 0.50; all pairwise P < 0.001), reflecting disproportionate elongation in predissection aortas. Aneurysm patients demonstrated diffuse thoracic dilation, whereas predissection group patients showed predominantly ascending aortic involvement. CONCLUSIONS: In a small exploratory study, predissection aortas displayed a distinct morphological phenotype characterized by disproportionate elongation, moderate dilation, and a relatively nondilated descending aorta-distinct from the diffuse dilation of aneurysm. Ascending aortic length and the AAL/MaxD ratio may provide complementary morphological information beyond maximal diameter alone.