Ascending Thoracic Aortic Aneurysms in a Veterans Affairs Health System: Longitudinal Outcomes and Risk Factors

Background The decision to perform ascending thoracic aortic aneurysm (ATAA) repair is primarily guided by diameter thresholds, but the optimal timing remains debated. We aimed to analyze ATAA outcomes in a large cohort of veterans. Methods Retrospective cohort study of patients with ATAA with diameter≥4.0 cm under surveillance between 1998 and 2024. Outcomes included surgical repair, all‐cause mortality, and aortic events. Fine–Gray competing risks regression evaluated the association of baseline diameter with all‐cause mortality, adjusting for age, hypertension, smoking, heart failure, and aortic valve phenotype. Results are reported as adjusted subdistribution hazard ratios (aSHRs) with 95% CIs. Results We included 764 veterans (98.0% male) with median (interquartile range) age of 75.0 (9.3) years, and ATAA diameter of 4.40 (0.50) cm. Median follow‐up was 5.4 (6.2) years. Surgical repair occurred in 86/764 patients (11.3%). Aortic dissection occurred in 2 patients (0.3%), both within the 4.0 to 4.5 cm group. All‐cause mortality rates were 2.83 (2.23–3.59), 3.22 (2.47–4.21), 5.82 (3.91–8.67), and 24.6 (12.2–54.1) deaths per 100 person‐years for ATAA diameters 4.0 to 4.4, 4.5 to 4.9, 5.0 to 5.4, and ≥5.5 cm, respectively ( P <0.001). In multivariable analysis, all‐cause mortality was independently associated with increasing ATAA diameter (aSHR, 1.36 per 0.5cm increase [95% CI, 1.14–1.63]; P <0.001) and increasing age (aSHR, 1.07 per year [95% CI, 1.05–1.09]; P <0.001). Conclusions ATAA all‐cause mortality increases with diameter, with a 7‐fold incidence increase in aneurysms ≥5.5 cm. Our findings support the 5.5 cm threshold for prophylactic ATAA repair and emphasize the need for selective intervention in smaller aneurysms.