The Non-syndromic Ascending Thoracic Aorta in a Population-based Setting of 60–74-Year-Olds: A Five-year Prospective Cohort Study from the Multi-center, Randomized DANCAVAS Screening Trials

Background: Prospective data on the ascending thoracic aorta are lacking. This study aimed to estimate growth rates and predictors of adverse aortic events (AAE).

Methods: In this prospective cohort study from the population-based, multicenter, randomized Danish Cardiovascular Screening trials (DANCAVAS), participants underwent cardiovascular risk assessments including non-contrast computed tomography (CT) scans. The clinical database was supplemented with data from nationwide Danish healthcare registries. Exclusion criteria were connective tissue disorders, bicuspid aortic valves, and AAE (thoracic rupture, dissection type A, thoracic aortic-related deaths) before inclusion. The cohort was followed until December 31, 2021, to monitor AAE, elective ascending aortic surgery, and death.

Results: Amongst 14,962 non-syndromic screened participants (95.0% men, mean age 67.7±3.7 years, mean follow-up 5.0±1.2 years), 2,026 individuals underwent ≥2 CT scans. The overall ascending aortic growth rate was 0.1±0.5 mm/year with no differences between small (<40 mm, n=1,374, mean 0.11±0.4 mm/year) and large (≥50 mm, n=76, mean 0.07±0.6 mm/year) (P=0.60) aortas ([Figure 1]).

Twenty-three individuals (0.2%) encountered AAE (31 per 100,000/person-years, 95%CI: 20.6-46.6), whilst 26 (0.2%) underwent elective ascending aortic surgery. In size-groups <40.0, 40.0-44.9, 45.0-49.9, 50.0-54.9, and ≥55.0 mm, proportions of AAE were 10/11,382 (0.1%), 5/2,997 (0.2%), 7/495 (1.5%), 0/74 (0.0%), and <3/16 (<19.0%), respectively. The mean time from scan to AAE was 2.2±1.7 years. Patients with familial disposition to aortic aneurysms had an adjusted hazard ratio for AAE of 3.9 (95%CI: 1.3-12.0, P=0.016). Using <40 mm as references, the adjusted hazard ratios were 11.1 (95%CI: 3.4-32.5, P<0.001) and 83.8 (95%CI: 9.7-726.4, P=0.027) for diameters 45.0-49.9 and ≥55.0 mm, respectively ([Figure 2]).

Conclusion: Prospective data from this large cohort showed remarkably low growth rates of the ascending aorta, which challenges the currently recommended (bi)annual surveillance scan interval. However, diameter ≥45.0 mm was a critical risk factor for AAE, indicating that the threshold for prophylactic surgery should be reduced.

Fig. 1 Violin Plots for the Growth Rates of the Ascending Aorta stratified by Baseline Ascending Aortic Size Groups. Estimated annual growth rates of the ascending aorta from linear mixed-effect modeling presented in violin plots and stratified by baseline ascending aortic size groups. The data are based on 4,897 non-contrast CT scans from 2,026 individuals (464 women; 1,562 men) with 1,374 below 40 mm, 388 between 40.0-44.9 mm, 188 between 45.0-49.9 mm, and 76 above 50 mm ascending aortic diameter at baseline, respectively. The central circles indicate medians, the boxes represent upper and lower percentiles, the dashed spikes denote the upper- and lower-adjacent values, and the surrounding overlays depict kernel-estimated densities of the annual growth rates by group, respectively.

Fig. 2 Adjusted Hazard Ratios for Adverse Aortic Events. Adverse Aortic Event was a composite outcome of rupture of the thoracic aorta, aortic dissection Type A, and thoracic aortic-related death. The hazard ratios were adjusted for age, sex, body surface area, baseline ascending aortic diameter, systolic and diastolic blood pressures, smoking history, peripheral arterial disease, diabetes mellitus, familial disposition to aortic aneurysms, and hypertension.