Wall shear stresses in small and large two-way bypass grafts

Wall shear stress, as one of the most important hemodynamic parameters of the cardiovascular system, has been studied extensively in the numerical and experimental approaches to blood flow in various arteries. In order to clarify the influence of graft diameter on the wall shear stress in a femoral two-way bypass graft, the pulsatile blood flows in two models were simulated with the finite element method. Both models were constructed with different diameters of grafts. The main geometric structure and the boundary conditions were identical for both models. The emphasis was on the comparison analysis of wall shear stresses in the vicinity of the distal anastomosis. The temporal-spatial distributions of wall shear stresses, wall shear stress gradients, and oscillating shear index were analyzed and compared. The present study indicated that femoral artery bypassed with a large graft demonstrated relatively uniform wall shear stresses and small wall shear stress gradients, whereas it does not have advantages in the oscillating shear index. The large model exhibits better and more regular hemodynamic phenomena and may be effective in decreasing the probability of the initiation and development of postoperative intimal hyperplasia and restenosis. Thus, appropriately large grafts are applicable in the clinical practice of femoral two-way bypass operation. More detailed studies are necessary on this problem for the purpose of increasing the success rates of the femoral bypass grafts.