Effect of Irregularities of Graft Inner Wall at the Anastomosis of a Coronary Artery Bypass Graft

摘要

It is well-established in medical literature that venous valves play a role in late segmental stenosis of vein grafts in the coronary artery bypass grafts (CABG). However, from the engineering point of view, vein grafts are always assumed as smooth tubes in the existing simulations, and no efforts have been put on the effects of vein valves and jagged-ness of the graft inner wall due to the competent valves (in case of reversed saphenous vein (SV) grafts) or the valve cusps remnants and valve sinus (in case of valve-stripped SV grfats) on the blood flow. In this preliminary study, the effects of the inner surface unevenness of a vein graft on the blood flow is investigated at the distal anastomosis with a more realistic geometry of valve-stripped SV, by means of numerical simulation of pulsatile, Newtonian blood flow. For this purpose, three CFD models of the distal anastomosis are designed, including one model with a smooth inner wall vein graft, one model with a vein graft containing one valve remnants and sinus, and one model containing two valve remnants and sinus in the graft. The proximal segment of the coronary artery is fully occluded in all models. The simulation results show that the valve remnants and sinus only cause some minor disturbances in the flow field and hemodynamic parameters (HP) just distal to the valve remnants, and not at the anastomosis. Therefore, assuming valve-stripped SV graft as a tube with a smooth inner surface will not affect the simulation results considerably at the anastomosis. This validates the assumption of smooth inner wall in case of bypass with valve-stripped vein grafts for simulation.