Effects of Anastomotic Angles and Distances of the Bypass Graft to the Stenosis on Blood Flow Hydrodynamics in a Bypass Grafting Coronary Artery

It is believed that the proper distance between the grafting location and the stenosis location and the appropriate angle of graft or transplantation in the blocked artery of the heart are two important factors in the removal or decrease of reappearance and re-development of intimal hyperplasia (IH), blood clotting, and re-blockage of the surgical artery. In the present study, a 3-D geometry of the host coronary artery as non-elastic with 75% symmetric axial cross-sectional area reduction is considered. The main assumptions were incompressible, laminar, steady-state, Newtonian, and non-Newtonian (with Herschel Bulkley model) blood flow. The 3-D Navier-Stokes equations coupled with the non-Newtonian constitutive model were solved numerically using a finite volume method with the procedure of the SIMPLE program. Shear stress distribution was obtained on the areas of potential re-obstruction and the occurrence of IH such as the Toe, Heel, arterial bed, suture location, and graft artery walls. Based on the results, the distribution of wall shear stress near the Heel, Toe location, and the intersection of the host and graft arteries suddenly increased dramatically. Wall shear stress (WSS) distribution was obtained in the areas of hyperplasticity re-incidence for some important anastomosis angles of grafted arteries, i.e. α=35°,45°,65°,75°. In addition, the increase in the angle of the graft artery caused a sharp increase in the shear stress on the area after the graft and the arterial bed in front of the branching region, and the shear stress decreases in the pre-graft region. Therefore, the excessive angle of the graft artery can cause damage to the arterial endothelial cells in the surrounding suture region.