Ascending aortic length across a large population presenting to the emergency room, a retrospective cross-sectional study.

Background: Aortic dissection often occurs at diameters below surgical thresholds, underscoring the need for better predictive markers. Ascending aortic length has emerged as a potential morphologic risk factor, but normal population data are limited. This study aimed to establish normative aortic length values by age and sex and develop a tool to predict dissection risk. Methods: We retrospectively analyzed 1030 (986 without and 44 with type A dissection) emergency room patients (from 1,445 screened) who underwent ECG-gated thoracic CT angiography between 2019 and 2025, excluding those with prior aortic surgery or disease. Ascending aortic length, from the sinotubular junction to the brachiocephalic trunk, was measured using semi-automated centerline tools. Logistic and LASSO regression models estimated type A dissection probability based on aortic length, age, height, and sex. Results: Mean ascending aortic length was 70.7 ± 11.6 mm in men and 64.1 ± 11.4 mm in women. Patients with acute type A dissection (n = 44) had significantly longer aortas (men: 93.9 ± 20.5 mm; women: 90.0 ± 18.5 mm; p < 0.001). Aortic length was the strongest independent predictor (OR = 1.13, 95 % CI 1.10-1.17, p < 0.001). A reduced model including only aortic length showed excellent discrimination (AUC = 0.871; sensitivity = 0.773; specificity = 0.867; PPV = 0.206; NPV = 0.988). Conclusion: Ascending aortic length increases with age and is markedly greater in patients with acute type A dissection. We provide normative reference tables by age and sex and a logistic model for individualized risk estimation of dissection at the time of the exam.