Study On Hemodynamics Of Coronary Artery Aneurysm And Bypass Grafts

Coronary artery aneurysm(CAA)is defined as a local coronary artery diameter expansion to the normal size of 1.5 times or more,which is a rare cardiovascular disease.The clinical manifestations of patients with CAAs are generally the same as those with narrow ischemic heart disease,such as angina pectoris,vasospasm or thrombosis,Usually saphenous vein graft(SVG)or left internal mammary artery(LIMA)are used to do bypass surgery.Because of it is rare,the mechanism of hemodynamics which causes ischemic is not entirely clear.The choice of two bypass grafts and CAA ligation or not rely mainly on the experience of doctors.It is lack of coronary quantitative evaluation of the influence of aneurysm and graft on hemodynamics.It is important to study and predict the hemodynamics of preoperative and postoperative aneurysm and bypass surgery.To reveal the mechanism of hemodynamics which causes ischemic and provide a reliable basis for clinical operation.To this end,this paper uses geometric multi-scale numerical simulation method to calculate the hemodynamics when SVG and LIMA were used as bypass graft.The contents of this paper include:(1)Hemodynamics of CAA.To build three models.The ratio of CAA diameter to adjacent coronary diameter was 2,3 and 5 respectively.The three dimensional model was coupled with the lumped parameter model for finite element calculation.Hemodynamics parameters wall shear stress(WSS),relative residence time(RRT)and vortex were analyzed.Describe the mechanism of ischemia.(2)Hemodynamics of SVG bypass surgery.To build SVG as bypass graft with ligation of CAA and normal CAA two models.Study on hemodynamics parameters about the blood flow,WSS and OSI of the SVG.Study on hemodynamics parameters about the WSS,RRT and vortex of the CAA.(3)Hemodynamics of LIMA bypass surgery.To build LIMA as bypass graft with ligation of CAA and normal CAA two models.Study on hemodynamics parameters about the blood flow,WSS and OSI of the LIMA.Study on hemodynamics parameters about the WSS,RRT and vortex of the CAA.The results show that:(1)With the increase of the volume of the CAA,the wall shear stress of the CAA decreased;the high RRT area increased;the vortex of the CAA increased.(2)When SVG is chosen as the bypass graft with the normal CAA,WSS of the SVG is in the range of 0.4-1Pa,the OSI is low and the blood flow rate is high.WSS of the CAA is basically the same as that before the operation.RRT is higher.And the vortex is reduced by 45.2%.When SVG is chosen as the bypass graft with ligation of the CAA,the WSS of SVG is in the range of 0.4-1Pa.The OSI is low and the flow rate is high.(3)When LIMA is chosen as the bypass graft with the normal CAA,the WSS of LIMA is in the range of 1-7Pa.The OSI is high and the blood flow rate is low.When LIMA is chosen as the bypass graft with the ligation of CAA,the WSS of the CAA is almost unchanged.And the high RRT area increased.And the vortex was reduced by 26.3%.The WSS of LIMA is in the range of 1-7Pa.The OSI is low and blood flow is high.The conclusions are as follows:(1)The low WSS and high RRT of the CAA can lead to the occurrence of thrombosis caused by endothelial cell disorder.So with the increase of the volume of CAA,the possibility of thrombosis increased easily lead to myocardial ischemia;increasing vortex easy caused vasospasm,causing poor blood vessels downstream.(2)SVG bypass surgery has a better physiological hemodynamic environment,but the WSS of SVG is in the transition range,the long-term effectiveness may be affected.(3)When LIMA is chosen as the bypass graft with the ligation of CAA,the hemodynamic parameters are good.When LIMA is chosen as the bypass graft with normal CAA,the OSI on the graft is high and blood flow is low.It easily leads to LIMA become invalid.It is not meet hemodynamic requirements.So when choose LIMA,the CAA should be ligatured.Through the study of hemodynamics of CAA,the part of hemodynamic mechanism is revealed.Studying the hemodynamics of bypass grafts can provides hemodynamic basis for clinical surgical decision.