Evaluation of the Natural History of the Proximal Descending Thoracic Aorta with Age

Background: Endovascular stent grafting has become an attractive alternative to the open repair of traumatic disruption of the aortic isthmus. However, the long-term consequences of this therapy are unknown. Since the majority of patients experiencing traumatic aortic disruption are young, anatomic changes of the thoracic aorta may become clinically important over time. The purpose of this study, therefore, was to examine the natural history of thoracic aortic diameter with progressing age.
Methods: From April to June 2006, 1000 consecutive thoracic CT scans performed for non-thoracic aortic pathology on patients age 15- 89 (mean age = 59.4 yrs) were examined, and thoracic aortic diameter immediately adjacent to the left subclavian artery was measured. Factors possibly influencing diameter, including age by decade of life (< 20 yrs, 20-29 yrs, 30-39 yrs, 40-49 yrs, 50-59 yrs, 60-69 yrs, 70-79 yrs, >80 yrs), race, gender, history of hypertension, diabetes, COPD, and tobacco use were examined. Factors were compared using the Students t-test.
Results: The differences in mean diameters of the thoracic aorta by gender (male = 27.1 v. female = 26.0, p = 0.87), race (Caucasian = 26.6 v. non-Caucasian = 26.3, p = 0.10), presence of hypertension (HTN = 25.8 mm v. no HTN = 24.9 mm, p = 0.36), COPD (COPD = 26.3 mm v. no COPD = 25.4 mm, p = 0.21), diabetes (DM = 26.1 mm vs no DM = 25.3 mm, p = 0.12), and tobacco use (tob = 26.3 mm v. no tob = 25.0 mm, p = 0.18) were not significant. However, differences in mean diameter over age were substantial as shown in Figure 1. Patients under 40 years old had mean aortic diameters of 22.92 mm compared to 27.09 mm (p<0.001) for patients over 40. The mean aortic isthmus diameter increases approximately 1 cm in size when comparing octogenarians to teenagers.
Conclusions: The diameter of the aortic isthmus increases substantially with age. While the clinical significance of this phenomenon for younger patients treated with endovascular stent grafts is unknown, these findings suggest that long-term surveillance is warranted to monitor the natural history of these grafts and to assess for possible late complications.