Fluid-structure interaction in an arteriovenous fistula: An assumption-related sensitivity analysis

Abstract

As the two-way coupled fluid-structure interaction (FSI) methodology has become a widely accepted numerical tool for solving biomedical engineering problems, several questions have arisen regarding the assumptions that must be made when employing FSI. This study focuses on the assumption-related sensitivity FSI analysis of an arteriovenous fistula (AVF) case. AVF is the widely accepted vascular access for hemodialysis, in which highly disturbed non-physiological blood flow is observed and mutual fluid-wall interaction is unavoidable. In the presented high-flow AVF, blood rheology played a minor role since the used Newtonian and non-Newtonian models overlap in the high-shear strain environment. Critical factors that play an important role in FSI simulations were analysed: 1) damping of loose connective tissue (LCT) embedding the AVF vasculature, 2) outlet pressure conditions and dealing with pressurization phase, 3) compliance of LCT, and 4) compliance of blood vessel walls. All of the above-mentioned mechanical factors to some extent affected the temporal quantitative results: lower damping can lead to wall vibrations resulting in biological response; correct procedure coping with the pressurization phase is of very high importance as data concerning the geometry of vasculature are acquired in the prestressed state; the total wall compliance resulting from the elasticity of walls and LCT remains unknown but may be responsible for significant differences in wall extension and temporal progression of hemodynamic parameters. However, when flow parameters are averaged over time, properly performed FSI produces comparable results to the rigid wall approach, which may be alternatively used to analyse hemodynamics in relatively small or stiff vascular models.