Quantifying the Structural and Mechanical Changes in Elastase Degraded Arteries as an In Vitro Model of Aortic Aneurysm

Abstract

Common characteristics of aortic aneurysm include loss of elastin/smooth muscle cells, increase in fibrillary collagen, and increase in artery diameter [5]. Because of the high mortality rate of aneurysm rupture, it is desirable to be able to predict when a patient should have surgery to repair the dilated tissue. Current clinical practices involve predicting aneurysm rupture based on artery expansion rate and diameter. However, other parameters such as wall stiffness and peak wall stress may offer better predictions as to when an aneurysm will fail [8]. Previous studies have investigated the differences in elastin and collagen content of abdominal aortic tissue with and without abdominal aortic aneurysm (AAA) [1]. In another study, human aortic aneurysm tissue was tested in a biaxial tensile tester and the resulting stress strain curves were fitted using Fung type exponential strain energy function [7]. More extensive modeling of aneurysm tissue has been done by modifying the Holzapfel model to incorporate a parameter that characterizes the tissue weakening before the failure of the inner elastic laminae, ground matrix, or collagen fibers themselves [6]. Previous studies have found compositional and mechanical differences between aneurysm and healthy tissue. In addition, good structurally based models for arteries that are developing aneurysm exist but these are mostly theoretical [6]. In order to improve aneurysm rupture prediction techniques, a better understanding of how structural changes affect the mechanical properties of the artery is necessary.