A realistic arteriovenous dialysis graft model for hemodynamic simulations

Abstract

Objective The hemodynamic benefit of novel arteriovenous graft (AVG) designs is typically assessed using computational models that assume highly idealized graft configurations and/or simplified boundary conditions representing the peripheral vasculature. The objective of this study is to evaluate whether idealized AVG models are suitable for hemodynamic evaluation of new graft designs, or whether more realistic models are required. Methods An idealized and a realistic, clinical imaging based, parametrized AVG geometry were created. Furthermore, two physiological boundary condition models were developed to represent the peripheral vasculature. We assessed how graft geometry (idealized or realistic) and applied boundary condition models of the peripheral vasculature (physiological or distal zero-flow) impacted hemodynamic metrics related to AVG dysfunction. Results Anastomotic regions exposed to high WSS (>7, ≤40 Pa), very high WSS (>40 Pa) and highly oscillatory WSS were larger in the simulations using the realistic AVG geometry. The magnitude of velocity perturbations in the venous segment was up to 1.7 times larger in the realistic AVG geometry compared to the idealized one. When applying a (non-physiological zero-flow) boundary condition that neglected blood flow to and from the peripheral vasculature, we observed large regions exposed to highly oscillatory WSS. These regions could not be observed when using either of the newly developed distal boundary condition models. Conclusion Hemodynamic metrics related to AVG dysfunction are highly dependent on the geometry and the distal boundary condition model used. Consequently, the hemodynamic benefit of a novel graft design can be misrepresented when using idealized AVG modelling setups.

Adaptation process of decellularized vascular grafts as hemodialysis access in vivo

“…This indicates good in vivo adaptation of the decellularized vascular grafts. Non-invasive ultrasound imaging showed that our model exhibited features similar to clinical cases, such as changes in hemodynamics [ 30 , 31 ] and vascular morphology [ 2 ]. By measuring the area change within the elastic lamina of the graft in HE staining, we found that the graft did not undergo expansion in the early post-transplantation period and only exhibited mild enlargement at arterial and venous ends after 1 year.…”

Hemodynamics and Wall Mechanics of Vascular Graft Failure

“…189 As in other vein grafts, CFD simulations have suggested that stenotic failures tend to localize with regions of low WSS and high OSI, 192 though the threshold values are related to the geometry and may require patient-specific models to identify clinical thresholds. 193 Alternative approaches to the standard vessel configuration have been proposed with recent high success rates observed for radial artery deviation and reimplantation, where the anastomotic stenosis associated with failure to mature is eliminated. 194 CFD in a rat model used to mimic this operation showed relatively lower pressures and WSS values in the vein with the artery-to-vein anastomosis, which could allow 136,178 The Dacron graft connects the aorta (green) to the femoral arteries (yellow) to bypass narrowing of the iliac arteries, which became fully occluded with the implantation of the bypass graft.…”