Biomechanical properties of ascending thoracic aortic aneurysms and mathematical characterization

Abstract

To properly understand the natural history of ascend ing thoracic aortic aneurysms (ATAA) and better assess their risk of rupture, stress analyses asking for biaxial biomechanical data of the tissue are necessary, but information on this matter is restricted in the literature. The present study addressed the role of ATAA on the biomechanical response of vessel wall. Degenera tive ATAA were excised from patients during graft replacement and non-aneurysmal age-matched vessels during autopsy. Uniaxi al tensile-tests were conducted on circumferential (CIRC) and longitudinal (LONG) tissue strips. The experimental recordings were reduced by a Fung-type strain-energy function that was found to be appropriate for characterization of the vessel's biome chanical response. The material parameters and rupture proper ties disclosed that ATAA and non-aneurysmal aorta were aniso tropic, i.e. stronger and stiffer in the CIRC direction. ATAA had no influence on tissue strength, but caused stiffening and exten sibility reduction. Our findings may serve as input data for the implementation of finite element models to be used as improved surgical intervention criteria. © 2011 Springer-Verlag Berlin Heidelberg.