Computational assessment of venous anastomosis angles and graft configurations in arteriovenous graft

Abstract

Arterio-venous grafts are a viable option for hemodialysis as long-term vascular access. The leading cause of Arterio-venous Grafts (AVG) failure is the development of intimal hyperplasia (IH), primarily found in vessel areas with unfavorable hemodynamic conditions. Computational Fluid Dynamics (CFD) is utilized in this study to assess the effect of some geometrical designs at venous anastomosis on these conditions.At first, models with various anastomosis angles are designed. Results represent that the maximum Wall Shear Stress (WSS) in the model with the anastomosis angle of 15° has decreased from 34.07 Pa to 17.48 Pa (48.69%) compared to the conventional model. Moreover, vortices and regions with high WSS at vein anastomosis reduce remarkably.In the second part, to lessen the unfavorable hemodynamic conditions inspired by the rotational blood flow in the aorta, the graft is designed with several cross-sectional ridges to induce a swirl flow. Three essential hemodynamic parameters, including Oscillatory Shear Index (OSI), Time Averaged Wall Shear Stress (TAWSS), and Relative Residence Time (RRT) in pulsating blood flow models, are extracted, and the outcomes are compared to conventional AVG.Finally, according to the results of the previous sections, an optimized model is proposed. Comparing this model with the conventional one illustrates more than 90% decrement in regions related to high OSI values and a 22.84% reduction in RRT values as the main hemodynamic parameters to assess the areas with a high risk of IH development.