Local mechanical properties of human ascending thoracic aortic aneurysms

Frances M. Davis1 · Yuanming Luo4 · Stéphane Avril2 · Ambroise Duprey2,3 · Jia Lu4
1 University of Southampton, Engineering Materials
2École Nationale Supérieure des Mines Saint-Étienne, CIS-EMSE, SAINBIOSE
3 Cardiovascular Surgery Service, CHU de Saint-Étienne
4 Mechanical Engineering, University of Iowa

Abstract. Ascending thoracic aortic aneurysms (ATAAs) are focal, asymmetric dilatations of the aortic wall which are prone to rupture. To identify potential rupture locations in advance, it is necessary to consider the inhomogeneity of the ATAA at the millimeter scale. Towards this end, we have developed a combined experimental and computational approach using bulge inflation tests, digital image correlation (DIC), and an inverse membrane approach to characterize the pointwise stress, strain, and hyperelastic properties of the ATAA. Using this approach, the pointwise hyperelastic material properties were identified on 10 human ATAA samples collected from patients undergoing elective surgery to replace their ATAAs with a graft. Our method was able to capture the varying levels of heterogeneity in the ATAA from regional to local. It was shown for the first time that the material properties in the ATAA are unmistakably heterogeneous at length scales between 1~mm and 1~cm, which are length scales where vascular tissue is typically treated as homogeneous. The distributions of the material properties for each patient were also examined to study the inter- and intra-patient variability. Large inter-subject variability was observed in the elastic properties.

Keywords: thoracic aneurysm, heterogeneous material properties, inverse elastostatic analysis, intra-patient variation, inter-patient variation, distribution of material properties.