Determination of the elastic modulus of ascending thoracic aortic aneurysm at different ranges of pressure using uniaxial tensile testing

Objective: The purpose of this study is to provide measurements of the elastic modulus of the aortic wall of ascending thoracic aortic aneurysms for different ranges of pressure (physiologic, hypertensive). In addition, pre-failure stress, taken as the peak stress obtained before specimen failure, was recorded for each test. Methods: Ninety-seven aortic samples freshly excised from 13 patients with ascending thoracic aortic aneurysms were obtained from greater and lesser curvatures and tested uniaxially in circumferential and longitudinal orientations. Results: The maximum elastic moduli, overall, and particularly in the lesser curvature were significantly higher in the circumferential orientation (9.19 MPa) than in the longitudinal (3.13 MPa). Results of peak stress showed positive correlation with maximum elastic modulus and inverse correlation with tissue wall thickness. Conclusions: This study provides new data on the elastic modulus in the physiologic and hypertensive range that can be used in computational analysis and the design of bench-top models. The accuracy of computational analysis and bench-top models strongly depends on the knowledge of the elastic properties of the aortic wall. The mechanical properties presented in this study, with specific values for 2 locations (greater and lesser curvature) and 2 directions (circumferential, longitudinal), will increase our understanding of the mechanisms that precede rupture of an ascending aortic aneurysm. (J Thorac Cardiovasc Surg 2011;142:682-6)