Fluid-structure interaction simulation of tissue degradation and its effects on intra-aneurysm hemodynamics

Abstract

Tissue degradation plays a crucial role in vascular diseases such as atherosclerosis and aneurysms. We present a novel finite element method-based approach to model the microscopic degradation of an aneurysmal wall due to its interaction with blood flow. The model is applied to study the combined effects of pulsatile flow and tissue degradation on the deformation and intra-aneurysm hemodynamics. Our computational analysis reveals that tissue degradation leads to a weakening of the aneurysmal wall, which manifests itself in a larger deformation and a smaller von Mises stress. Moreover, simulation results for different heart rates, blood pressures and aneurysm geometries indicate consistently that, upon tissue degradation, wall shear stress increases near the flow-impingement region and decreases away from it. These findings are discussed in the context of recent reports regarding the role of both high and low wall shear stress for the progression and rupture of aneurysms.

On the Potential Self-Amplification of Aneurysms Due to Tissue Degradation and Blood Flow Revealed From FSI Simulations

“…As mentioned above, in this work, we use a recently developed FSI framework to account for the interaction between blood flow and aneurysmal walls, and at the same time to capture the degradation of vascular tissues (Wang et al, 2021b). In this computational framework, a tissue degradation model (Balzani et al, 2012;Anttila et al, 2019) is combined with the opensource software, SimVascular/svFSI (2021) which is finiteelement-method-based and uses an arbitrary Lagrangian-Eulerian formulation of Navier-Stokes equations to model incompressible Newtonian fluid (blood) flows on moving domains (Vedula et al, 2017).…”

“…The degradation model employed here has been validated in previous studies (Balzani et al, 2012;Anttila et al, 2019) and proved to reproduce the experimental cyclic responses of different types of arteries. The current model is able to account for stress softening (Balzani et al, 2012;Anttila et al, 2019;Wang et al, 2021b), a phenomenon commonly observed in biological tissues. The present study is qualitative research and a first step toward a more realistic model.…”

“…The inner diameter of the spherical cap (aneurysm) is 1.0 cm. The mean diameter of the parent vessel Following the literature, the wall thickness has been chosen to be 0.04cm (Isaksen et al, 2008;Wang et al, 2021b). As shown in Figure 2, a variation of wall thickness by a factor of three (from 0.02 to 0.06 cm) leads to less than 15% change in degradation-induced effect on strain.…”

“…On the other hand, degradation-induced changes in mechanical properties of an aneurysmal wall may have an influence on hemodynamics inside the aneurysm, which is poorly studied though. Recently, we have developed a novel computational framework by combining a tissue degradation model and a finite element-based fluid-structure interaction (FSI) solver (Wang et al, 2021b). Using this model, we have shown that TAWSS increases near the flow-impingement region of idealized aneurysms and decreases away from it in the process of degradation (Wang et al, 2021b).…”

“…Recently, we have developed a novel computational framework by combining a tissue degradation model and a finite element-based fluid-structure interaction (FSI) solver (Wang et al, 2021b). Using this model, we have shown that TAWSS increases near the flow-impingement region of idealized aneurysms and decreases away from it in the process of degradation (Wang et al, 2021b).…”