Can sites prone to flow induced vascular complications in a-v fistulas be assessed using computational fluid dynamics?

Arterio-venous fistulas (shunts between arteries and veins) are the preferred vascular access for hemodialysis. Despite their superior patency, compared with synthetic tubes and grafts, functional problems and inadequate flow rates are the common complications. Local flow conditions, in particular low and oscillating wall shear stresses (WSS), are central to vascular problems and a robust framework for analyzing flow conditions in vascular structures could provide an understanding of the mechanisms leading to vascular complications, such as stenoses, aneurisms, and thromboses. We hypothesize that a validated computational fluid dynamics (CFD) framework can be used to identify critical fistula configurations with elevated risk of complications. Therefore, the aim of the present study was to develop a CFD framework for analyzing fluid flow in complex vascular structures, such as arterio-venous fistulas validated by comparisons of in vitro volume flows with CFD results and flow fields from ultrasound scans with CFD simulations. Volume flows measured in vitro and CFD data differed quantitatively. However, good relative correlations exist between the data using logarithmic scales. Qualitatively, visual comparisons between ultrasound and CFD images showed good agreement between the two methods. In addition, WSS levels and the oscillatory shear index (OSI) were calculated and visualized on the model surface. The method was successfully validated and the method is deemed suitable for more thorough investigations into the field of vascular complications in a-v fistulas.