Study On The Effect Of Fluid Shear Stress On The Systolic And Diastolic Function Of Coronary Arteries

Objective: Cardiopulmonary bypass(CPB)is a precondition for the success of most open heart surgeries,up to now,the ischemia reperfusion injury to coronary endothelial cells and myocardium caused by blocking CPB is still an important reason for the high postoperative complications and mortality of patients undergoing heart surgery.In this study,the structure of coronary endothelial cells and the vasomotor function of coronary vessels were observed to investigate the effect of shear stress on coronary endothelial cells and the vasomotor function of coronary vessels.Methods: In this study,Chinese type piglets were randomly divided into three groups:(1)Normal low limiting pressure continuous perfusion group;(2)normal high pressure limiting continuous perfusion group;(3)The conventional CPB group.The double-bypass model was used to continuously perfuse the coronary circulation of Chinese type piglets at different pressures to detect the hemodynamic indexes,and then the coronary vascular ring was prepared to detect the vasomotor function.Finally,the coronary endothelial cells were observed by transmission electron microscopy and highpower electron microscopy.Results:(1)The changes of HR,MAP and CVP in the three groups with time showed that from T2,T3,T4 and T5 all accelerated HR,decreased MAP and increased CVP compared with T1(P < 0.05),but there was no statistical significance between the groups(P > 0.05).Both left ventricular end-systolic pressure(LVSP)and left ventricular end-diastolic pressure(LVEDP)were decreased after CPB(P < 0.05),but there was no statistical significance among the three groups(P > 0.05).The +dp/dtmax and-dp/dtmax in the three groups also decreased to different degrees after CPB,and the decrease of +dp/dtmax in the conventional CPB group and the high perfusion pressure group was higher than that in the low perfusion pressure group(P < 0.05).There was no significant difference in the decrease of-dp/dtmax among the three groups(P > 0.05).(2)The vascular ring systolic and diastolic function of the three groups showed that the vascular ring activity of the normal low pressure limiting continuous perfusion group was better than that of the normal high pressure limiting continuous perfusion group(P < 0.05),and the normal high pressure limiting continuous perfusion group was better than the conventional CPB group(P < 0.05).However,compared with normal coronary rings without CPB,systolic and diastolic function of coronary rings decreased in all three groups,showing no statistical difference.(3)The results of transmission electron microscopy and high-power electron microscopy indicated that the coronary endothelial cell injury in the conventional CPB group and the high-perfusion pressure group was more serious than that in the normal perfusion group.Conclusions: The shear stress affects the structure of coronary endothelial cells and the systolic and diastolic function of coronary vessels.