THE EFFECT OF ASYMMETRY AND AXIAL PRESTRAINING ON THE AMPLITUDE OF MECHANICAL STRESSES IN ABDOMINAL AORTIC ANEURYSM

Abstract

In this work we study the effect of asymmetry and axial prestraining on the maximum effective mechanical stress in relatively small human abdominal aortic aneurysm (AAA) during a cardiac cycle. Our model is based on the fluid-structure interaction (FSI) methodology. The arterial wall is modeled using large strain and large deformation formulation, with hyperelastic material behavior, and isotropic nonlinear strain energy function (SEF) fitted to the averaged data set of biaxial tests of AAA tissue specimens. The results confirm that the magnitude of the maximum von Mises stress increases significantly with asymmetry and decreases with aneurysmal length. It is found that the amplitude in variation of the maximum effective stress changes in the same manner as the maximum stress. These results indicate that a short asymmetric AAA is under significant dynamic stress, which might be one of the important factors in a progressive AAA growth over time. It is also found that, in most considered cases, magnitude and amplitude of the maximum effective stress of an AAA is smaller when the artery is pre-stretched in axial direction, while a pre-stretched artery with aneurysm has slightly larger relative volume change of lumen during cardiac cycle than the unstretched AAA.