Hemodynamic Research On Surgical Planning Of Coronary Artery Bypass Grafting

Coronary artery bypass surgery,also known as coronary artery bypass grafting(CABG),is a surgical procedure consisting of either diverting the left internal thoracic artery(LITA)to the left anterior descending(LAD)branch of the left main coronary artery;or a harvested great saphenous vein(SV)of the leg,attaching the proximal end to the aorta or one of its major branches,and the distal end to immediately beyond a partially obstructed coronary artery.The purpose is to restore normal blood flow to that partially obstructed coronary artery.While,the hemodynamics will affect the short-and long-term surgical results directly.If the SVG is used to bypass the coronary stenosis,dangerous hemodynamics may exist at the surgical site,which may lead to intimal hyperplasia and even the re-stenosis at the anastomosis or some other graft lesions.All these post-operative lesions will decrease the long-term patency of CABG.The LITA is the choice of graft for CABG due to the excellent long-term patency when grafted to the LAD coronary artery.However,many reports of LITA graft failure exist due to the so-called string phenomenon.While now,the surgical planning of CABG is mainly based on clinical experience,there should be a useful surgical planning system based on the hemodynamic evidence.The structure and lesion of coronary artery are patient-specific,so the surgical planning system should not only be general but also can be patient-specific.For this purpose,the general lumped parameters model of coronary arteries,which can be used in patientspecific surgical planning,was built in this study,based on the typical coronary structure.Moreover,the geometrical multiscale model of coronary arteries was constructed by coupling the lumped parameters model with patient specific threedimensional model of coronary arteries.Based on these two models,the hemodynamic research method on the CABG surgical planning was constructed to predict the postoperative hemodynamics and its effects to the surgical results.Moreover,some suggestions and references for the clinical surgical planning can be provided.The topics of this thesis contains:(1)Hemodynamic research on the SVG.In this study,two researches on the surgical decision of SVG were finalized based on the patient specific geometrical multiscale model.First,the hemodynamic difference among the normal graft,Y-type graft and sequential graft was compared and discussed;Second,whether the coronary branch without stenosis should be bypassed or not for the preventive purpose was studied.Results show that the short-term results,such as the graft flow and the coronary flow,of the normal graft,sequential graft and the Y-type graft are almost the same.But,by comparing the low WSS and the high OSI distributions of different grafts,it can be found that large area of low WSS distribute on the Y-type and normal graft.That means the long-term patency of the sequential graft may be better than normal graft and the Ytype graft.If the coronary branch without stenosis was bypassed for the preventive purpose,part of the blood will flow to the distal through the coronary artery.This will lead to large area of low WSS distribution on the graft.This may affect the long-term patency of the graft,so the branch without stenosis should not be bypassed for the preventive purpose.(2)Hemodynamic research of the LITA graft.In this study,the hemodynamic feature of the LITA grafted to the LAD with moderate stenosis and its relationship with the competitive flow was discussed by comparing it with that in serious stenosis condition.Moreover,the difference between LITA graft and SV graft was also studied and reported.Results show that the high OSI is the main hemodynamic feature of string phenomenon in LITA.While,the low WSS is not the main hemodynamic factor.(3)Surgical planning software based on LPMIn this study,a surgical planning software was developed based on the LPM of coronary system.Within this software,the parameters of the LPM will be modified personalized according to the patient information.Then,some different post-operative LPMs will be built based on different surgical plans designed by the surgeon.Finally,the results of these LPMs,such as the graft flow,myocardial perfusion,average wall shear stress(WSS)and oscillation shear index(OSI)on the graft will be displayed on the interface of the software.These results will help the surgeons to predict the results of different surgical approaches.This study is focus on the surgical planning and short-/ long-term surgical results of CABG.Some surgical planning methods and suggestions for the long-term patency of SVG was provided.The hemodynamic of string phenomenon in LITA was clarified.Furthermore,some references for the prediction of the competitive degree and the probability of string phenomenon were provided.Moreover,a general CABG planning software,which can be used for patient-specific surgical planning,was developed in this study.In general,the theoretical basis and reference of CABG hemodynamic surgical planning were provided in this study.Moreover,it has potential value to promote the clinical application of hemodynamic surgical planning in CABG.