Effect Of Carotid Bifurcation Angle On Hemodynamics And Its Correlation With Atherosclerosis

PART 1 Correlation between different carotid bifurcation angles and plaque formation at carotid bifurcationObjective(s): In this study,computed tomography angiography(CTA)technology was used to observe and analyze the carotid bifurcation Angle and the atherosclerotic plaque at the carotid bifurcation,and the subjects were divided into groups according to the carotid bifurcation Angle.In order to observe the correlation between different carotid bifurcation angles and the formation of atherosclerotic plaque at the origin of the internal carotid artery,so as to provide reference for clinical research on this disease.Methods: The head and neck CTA images of 97 subjects who met the study criteria in our hospital were retrospectively analyzed.The geometric morphology of194 carotid artery bifurcation was detected and divided into small Angle group(<45.37°),average Angle group(45.37°～68.43 °)and large Angle group(> 68.43°)according to the Angle of common carotid artery bifurcation.At the same time,whether there was atherosclerotic plaque at the carotid bifurcation was examined to observe and compare the effects of different carotid Angle groups on the formation of plaque at the carotid bifurcation.Results:(1)There were no significant differences in clinical baseline data(including gender,age,BMI,hypertension,diabetes,dyslipidemia,smoking history,and alcohol history)among the small-angle group,the average Angle group,and the large-angle group(P > 0.05).(2)The plaque detection rates of small Angle group,average Angle group and large Angle group were 28.3%,40.5% and 62.0%,respectively.There was no significant difference in plaque detection rate between the mean Angle group and the small Angle group(P > 0.05).There were significant differences in plaque detection rate between the large Angle group and the small Angle group,and between the mean Angle group(P < 0.05).Conclusion(s):(1)The detection rate of plaque in small Angle group,average Angle group and large Angle group increased.(2)The detection rate of plaque in the large Angle group was higher than that in the small Angle group and the average Angle group.PART 2 Computer simulation study on the effect of different carotid bifurcation angles on convective mechanicsObjective(s): In this study,an ideal model of carotid bifurcation with different angles was established,and Computer fluid dynamics(CFD)technology was used to simulate the ideal model of carotid bifurcation in order to observe the effect of different carotid bifurcation angles on hemodynamics.This study provides a mechanical reference for exploring the relationship between carotid bifurcation Angle and carotid atherosclerosis(CAS).Methods: According to the geometric measurements of the subjects in the first part,the ideal models of 25°,50°,75° and 100° carotid bifurcation were established respectively.The ideal models were imported into Materialise 3-matic software for smooth processing,and then imported into Ansys 2021 R2 software for mesh division and numerical simulation.The distribution maps of wall shear stress(WSS),wall pressure,blood flow line and flow velocity at the time of peak flow velocity were obtained after processing by CFD-Post software.Results:(1)Ansys 2021 R2 software was used for meshes: a total of 151878 internal nodes and 1153760 internal grids were generated by the 25° model.The 50° model generated 138207 internal nodes and 1221669 internal grids.The 75° model generated a total of 133797 internal nodes and 1184204 internal grids.The 100° model generated a total of 132,731 internal nodes and 1174,461 internal grids.(2)The magnitude and distribution of wall shear stress at the time of peak flow velocity: the WSS of the main vessel was slightly lower,and the lower WSS area was observed locally.When blood flow was shunted,areas of low WSS appeared near the bifurcation and on the lateral wall of the bifurcation.With the increase of the bifurcation Angle,the low-WSS region extended to the trunk,the area involved in the low-WSS region was wider,and the variation amplitude increased.At the same time,with the increase of the bifurcation Angle,the WSS near the bifurcation and the lateral wall of the bifurcation gradually became smaller,extending downstream of the blood vessel.(3)The magnitude and distribution of wall pressure at the peak flow velocity: at the peak flow velocity,the wall pressure of the whole carotid bifurcation showed a gradual downward trend from the main vessel to the downstream of the bifurcation,but the pressure near the bifurcation was higher.As the Angle increases,the pressure near the bifurcation increases significantly,and the higher pressure is distributed over a larger area of the inner wall of the bifurcation.(4)Blood flow line and core area distribution of vortex at the time of peak flow velocity: blood shunts could be observed near the blood vessel bifurcation in different bifurcation models,and the core area distribution of vortex could be observed near the bifurcation.With the increase of the carotid bifurcation Angle,the effect of blood diversion is more obvious,the change of blood flow direction is greater,the streamlines are more sparse,and the recirculation zone appears.At the same time,the core region of the vortex became larger and extended from the vicinity of the bifurcation to the downstream of the vessel,mainly concentrated in the vicinity of the bifurcation and the lateral wall region of the bifurcation.(5)The velocity and distribution of blood flow at the time of peak velocity: near the bifurcation of the bifurcation models with different angles,there was a velocity collapse zone in each model.After the bifurcation,the blood flow velocity gradually increased,and the flow velocity of the lateral wall of the bifurcation was lower than that of the medial wall of the bifurcation.After the change of bifurcation Angle,the velocity and direction of blood flow after bifurcation changed regularly.With the increase of the bifurcation Angle,the decrease of flow velocity near the bifurcation further increases,and the distribution of lower velocity area becomes larger.After bifurcation,the direction of blood flow changed significantly,the length also changed greatly,and the length of the vector became uneven.Conclusion(s):(1)The change of carotid bifurcation Angle has a certain effect on hemodynamics.(2)The distribution of wall shear stress,wall pressure,blood flow streamline and blood flow velocity at different carotid bifurcation angles can be visualized by CFD technology at the time of peak flow velocity,which provides certain help for the effect of carotid bifurcation Angle on hemodynamics.