Computational haemodynamics analysis and comparison study of arterio-venous grafts.

Haemodialysis arterio-venous graft failure is related to the development of stenotic lesions most commonly located near the venous anastomosis, especially in the toe region. 'Disturbed flow' interaction with the vessel wall surface, characterized by haemodynamic parameters based on the local wall shear stress or the radial pressure gradient, have been widely recognized as the trigger mechanism of a cascade of abnormal biological events leading to occlusive developments. Assuming incompressible laminar flow and rigid, in-plane vessel walls, validated haemodynamics are numerically simulated for a constant-diameter end-to-side base case, the Venaflo graft, and an improved graft-end configuration. The geometric design of the new graft-end was based on the reduction of three time- and area-averaged haemodynamic parameters, i.e. the wall shear stress gradient, wall shear stress angle gradient, and radial pressure gradient. Considering the critical toe region, the Venaflo graft has demonstrated measurable improvements over the base case configuration in predictive computer simulations as well as in clinical trials. The performance improvement should be further enhanced with the modifications illustrated by the new design.