David A. Guel, Matthias Peltz, Amit Khera,

1. Changes in Diameter of the Descending Thoracic Aorta with Age: Implications for Thoracic Endovascular Aneurysm Repair David A. Guel, Matthias Peltz, Amit Khera, Donald D. McIntire, Ronald M. Peshock, Michael E. Jessen, UT Southwestern Medical Center, Dallas, TX

2. Introduction: • Thoracic Endovascular Aneurysm Repair (TEVAR) has proven effective for treating descending thoracic aneurysms but long term results are unknown. • One concern is whether the endograft will remain stable over time if the aorta grows in size. • This study applied information from a large unselected contemporary community population to define normal aortic dimensions and to examine the relationships between aortic size and patient age.

3. Methods: • Data were provided from a validated multiethnic, population-based probability sample from an urban community. Adults 18 - 65 years of age underwent collection of demographic and medical history data. • A subset of participants (n=2643) underwent gated aortic magnetic resonance imaging and the diameter of the descending aorta at the level of the pulmonary artery bifurcation was measured.

4. Methods: • Age, gender, ethnicity (white, black, Hispanic or other) and multiple indices of body size and composition were collected (including height, weight, waist circumference, hip circumference) or calculated from available data (body mass index [BMI], body surface area [BSA], allometric height [AlloH]). • Data from dual-energy x-ray absorptiometry was used to calculate total body fat mass and lean body mass.

5. Methods: • A univariate analysis was performed relating descending aortic diameter to each variable. • A stepwise multivariable regression analysis was used to identify variables independently associated with aortic size. • A p-value < .05 was considered significant.

6. Results: • By univariate analysis, increased aortic size was associated with: • increased age, male gender, black ethnicity, • greater height, greater weight, • greater waist and hip circumference, • greater BMI, greater BSA , greater AlloH, • greater total body fat mass, and • greater total body lean mass.

7. y = age * 0.128 + 19.358 r=0.411, p<0.0001, n=2643

8. Correlation Between Ascending Aortic Diameter and Gender P<0.0001 by t-test

9. Correlation Between Ascending Aortic Diameter and Ethnicity P<0.05 by one-way ANOVA

10. Results: • Multivariable analysis determined the following: • Greater age remained significantly associated with greater aortic size (p<0.0001). • Lean body mass (p<0.0001), ethnicity (p<0.0001), gender (p=0.0001), waist circumference (p<0.0001) and hip circumference (p=0.0295) also emerged as significant determinants of descending aortic diameter.

11. Conclusions: • The diameter of the descending aorta appears to increase with age and is larger in subjects with greater lean body mass and greater hip circumference. • While the diameter of the descending thoracic aorta progressively increases over time, this increase in diameter averages only about 5.1 mm over 40 years. • This degree of aortic enlargement is unlikely to affect most patients who undergo treatment with TEVAR, even when treated at a young age.

12. Study Limitations: • The area examined is the proximal descending thoracic aorta and many endografts are seated in the transverse arch, or distal aorta – areas not assessed in this study. • The study does not apply serial assessments of the same patients – rather the analysis is done by comparing aortic size over a population with a range of ages. • The study population is unselected, and therefore approximates a “normal” population, whereas endografts are placed in patients with aortic pathology (with the exception of those treated for aortic trauma). • The behavior of the aortic wall over time may be different after an endograft has been placed.