Characterizing the mechanical properties of the aortic wall

Characterizing the physical properties of the aortic wall is essential to understanding the causes of cardiovascular diseases, such as aneurysms. Modelling compliant, anisotropic, multilayered tubes such as the aorta has proven to be a challenge. In vitro studies of the mechanical properties of arteries incorporate a variety of testing methods; however, the majority of these tests fail to replicate the complex, transmural loading conditions arising from pulsatile flow. These methods include typical tensile tests, both in uniaxial and biaxial set-ups, bulge inflation tests and extension-inflation tests. Bulge-inflation tests grant material information in response to biaxial loading but still do not mimic proper cylindrical loading conditions. Extension-inflation tests capture the cylindrical loading but have only been performed with static pressurization and with rigid boundary conditions in effect. This review aims to present the current state of the biomechanical characterization of arterial walls, particularly the aorta, through discussion of testing methods and their findings. We emphasize literature that focuses on prediction of aneurysm rupture risk. Moreover, overarching concepts such as histological effects, age dependent effects, segmental effects, hemodynamic effects, viscoelastic modelling and torsion will be briefly explored. An understanding of the current limitations of testing will hopefully lead to the development of more robust in vitro test methods that will further elucidate the relationship between changing vessel wall mechanics and cardiovascular disease