Design Of Mechanical Anastomotic Devices And Numerical Simulation For Coronary Artery Bypass Grafting

Coronary-artery bypass grafting, CABG for short, is the most effective way totreat coronary heart diseases. For end-to-side anastomosis between graft vessel andaorta, traditional suturing method needs to clamp the aorta and it takes long time,besides, it requires high operating skills. The mechanical anastomotic method canaccomplish the process within short time and avoid aorta-clamping on nonstoppressured transportation pipeline. This paper is for the purpose of designingmechanical anastomotic devices. The anastomotic geometry has two features by usingthe connector provided in the paper: one is the bulge and the other is the difference ofthe straight portion length of the graft. In order to study the hemodynamiccharacteristics caused by two features in mechanical method and explore the factorsthat will affect the long-term patency in CABG, three-dimensional unsteadysimulations have been done by using the methods of computational fluid dynamics.The main research contents and results are listed as follows:(1) Based on current mechanical anastomotic devices, we provided a type ofanastomotic connector and designed an aortic opening and graft-released device,which could accomplish the punching and anastomosis in a short and simple way.(2) Based on the actual flow in cardiovascular, laminar model was used in thisstudy. Differential equations were discretized by a second-order upwind scheme, andSIMPLE algorithm was used for numerical calculation. Unstructured grid was usedfor meshing and boundary layer mesh was used near the wall, besides, gridrefinement was done near the anastomosis area, all of which would improve thereliability of the numerical calculation.(3) Numerical simulation was done about the bulge in mechanical anastomosis.Results showed that using the mechanical anastomotic devices enlarged the area oflow velocity while increasing the magnitude of the velocity in grafts. The wall shearstress in anastomosis changed dramatically, besides, stress concentration was moreserious, which would lead to the activation of the platelets and intimal hyperplasia.Optimal design of mechanical anastomotic devices was necessary to avoid the bulge.(4) Numerical simulation was done about the difference of straight portionlength of the graft. Results showed that hemodynamic characteristics were better inthe shorter model, the anastomosis area of which was featured with relatively smoother flow field, larger wall shear stress and smaller wall shear stress gradient.Besides, vortex center of the secondary flow was far away from the wall in the shortermodel. Those results had good effects on retarding intimal hyperplasia and improvingthe long-term patency in CABG.The results of this research have important theoretical sense and practical valuein clinical application of mechanical anastomotic devices in CABG.