Influence of a Poro-Mechanical Modeling of the Intra-Luminal Thrombus and the Anisotropy of the Arterial Wall on the Prediction of the Abdominal Aortic Aneurysm Rupture

Abstract

In order to improve the prediction of the Abdominal Aortic Aneurysm (AAA) rupture, a more comprehensive modeling is proposed, considering the porous nature of the Intra-Luminal Thrombus (ILT), the hyperelastic anisotropy of the AAA wall and fluid-structure interactions. Then, numerical simulations are performed on idealized AAAs. The results permitted to recover previous in vivo measurements of the intra-thrombus blood pressure. It is shown that the maximum pressure transmitted, through the ILT, to the AAA wall is about 10% lower than the pressure in the lumen. Despite this small decrease, the maximum stress (σ 1max) within the AAA wall strongly decreases when the relative volume of ILT increases. This new modeling is compared with classical modelings (dense hyperelastic ILT or hyperelastic isotropic AAA wall) by highlighting the influence of the mechanical modeling of the AAA wall and the ILT on the wall stress and the Peterson’s modulus (E P) of the AAA. This comparison shows that the magnitude and the location of σ 1max strongly depend on these modelings and that classical modelings overestimate the above decrease of σ 1max when the relative volume of ILT increases. Finally, the evolution of σ 1max with respect to E P is investigated. It is shown that, whatever the ILT modeling, the increase of its relative volume leads to a decrease of σ 1max and an increase of E P, for the isotropic AAA wall, while both σ 1max and E P decrease, for the anisotropic AAA wall. All these results point out that the prediction of the potential risk of the AAA rupture can be strongly affected by the coupling of (i) the mechanical modelings of the AAA wall and the ILT and (ii) the distribution of the latter within the aneurysm.