Hemodynamic Study Of Carotid Atherosclerosis Using CFD Based On Three-Dimensional Images

Part I: Association Between Formation of Carotid Atherosclerotic Plaque and Local Hemodynamics Using CFD Based on Three-dimensional ImagesObjective: To compare the difference of wall shear stress(WSS),pressure,blood flow velocity and flow pattern between plaque-prone area and other areas in normal carotid artery in vivo,using computational fluid dynamics(CFD)based on three-dimensional contrast enhanced-magnetic resonance angiography(CE-MRA)images and to discuss the association between formation of carotid atherosclerotic plaque and local hemodynamic factors.Materials and Methods: Sixteen carotid arteries without atherosclerotic plaque confirmed by carotid MR imaging were enrolled in our study.Original CE-MRA images were obtained for three-dimensional reconstruction.CFD analysis was then performed to estimate WSS,pressure,blood flow velocity and flow pattern in atherosclerosis-prone(sinus)and other areas(distal common carotid artery and distal internal carotid artery)in normal carotid artery.One-way analysis of variance was conducted to analyze differences among these areas.Results: CFD analysis revealed that WSS and velocity were significantly lower in sinus compared to distal common carotid artery(CCA)(P=0.011,P<0.001,respectively)and distal internal carotid artery(ICA)(P<0.001,P<0.001),and formed a vortex in sinus.While in-plane pressure difference was significantly higher in sinus compared to distal CCA(P <0.001)and distal ICA(P =0.005).Conclusion: Hemodynamic environment in sinus of normal carotid artery assessed using CFD analysis which appeared to be with lower WSS,higher in-plane pressure difference,lower velocity and formed vortex.These characterizations might facilitate the formation of atherosclerotic plaque.Part II: CFD Study of Local Hemodynamic Parameters Variation in Stenotic and Stenosis-repaired Carotid Arteries Based on Three-dimensional ImagesObjective: To study the variation before and after the formation of carotid atherosclerotic(CAS)plaque using vessel surface repaired method simulating normal carotid artery and to discuss the association between formation and development of carotid atherosclerotic plaque and local hemodynamic factors.Materials and Methods: Sixteen carotid arteries with sinus atherosclerotic plaque only confirmed by carotid MR imaging were enrolled in our study.Original three-dimensional(contrast enhanced-magnetic resonance angiography)CE-MRA images were obtained for three-dimensional reconstruction.The stenotic segments of carotid arteries were repaired by vessel surface repaired method to simulate normal carotid arteries.Computational fluid dynamics(CFD)analysis was performed to estimate wall shear stress(WSS),pressure,blood flow velocity and flow pattern in sinus and other areas in stenosis-repaired carotid artery,sinus before and after repaired,sinus in stenosis-repaired carotid artery and upstream and downstream of stenosis in stenotic carotid artery.Results: Compared with other areas(inner lateral internal carotid artery opposite to sinus,inner and outer lateral at common carotid artery and internal carotid artery)in stenosis-repaired artery,sinus demonstrated significantly lower WSS(4.66 vs.14.30,7.05,6.51,8.71,12.20 Pa,P<0.05,respectively)and lower velocity(0.43 vs.1.20,0.79,0.94,1.29,0.91m/s,P<0.05,respectively),and formed a vortex.Compared with common carotid artery level and internal carotid artery level in stenosis-repaired artery,sinus demonstrated higher in-plane pressure difference(202 vs.37,143 Pa,P <0.05,respectively).Compared with carotid sinus in stenosis-repaired carotid artery,the WSS in the upstream of stenosis in stenotic carotid artery was lower(3.44 vs.4.66 Pa,P<0.05)while in the downstream area was similar(5.16 vs.4.66 Pa,P=0.87),both upstream and downstream of stenosis were demonstrated similar velocity to carotid sinus in stenosis-repaired carotid artery(0.43,0.21 vs.0.43m/s,P=0.76,P=0.36,respectively).Both the upstream and downstream of stenosis formed vortex.Conclusion: Using the vessel surface repaired method to simulating normal vessel as follow up study of carotid plaque formation is feasible,economical,and simple.Atherosclerosis-prone areas harbor a hemodynamic environment characterized by lower WSS,higher in-plane pressure difference,lower velocity and formed vortex,favoring the formation of atherosclerosis.The hemodynamic characters of upstream and downstream may relate to the progress of atherosclerotic plaque.Part III: Association Between Rupture of Carotid Atherosclerotic Plaque and Local Hemodynamics Using CFD Based on Three-dimensional ImagesObjective: To analyze the hemodynamic characteristics in prone-rupture area of carotid atherosclerotic(CAS)plaque using vessel surface repaired method simulating pre-rupture plaque and to explore the possible hemodynamic factors lead to plaque rupture.Materials and Methods: Thirteen carotid arteries with ruptured atherosclerotic plaques confirmed by carotid MR imaging were enrolled in our study.Original three-dimensional contrast enhanced-magnetic resonance angiography(CE-MRA)images were obtained for three-dimensional reconstruction.The rupture area of carotid plaque was repaired by vessel surface repaired method to simulate pre-rupture plaque.Computational fluid dynamics(CFD)analysis was performed to estimate hemodynamic factors in prone-rupture area,other area,before and after rupture.Results: All of the thirteen rupture sites were located in proximal side of plaque.In rupture-repaired carotid plaque,compared with other area,the proximal side of plaque demonstrated significantly higher wall shear stress(WSS)(160 vs.92 Pa,P<0.0001),higher pressure(18070 vs.10295 Pa,P<0.0001)and larger velocity(11.46 vs.7.5m/s,P<0.0001).And form a high pressure difference on prone-rupture plaque.The WSS,pressure and velocity was lower(1.63 vs.160 Pa,7023 vs.18070 Pa,1.56 vs.11.46m/s,P<0.0001,respectively)when the plaque was rupture.Conclusion: Using the vessel surface repaired method to simulating pre-rupture plaque as follow up study of carotid plaque rupture is feasible,economical,and simple.The proximal side of pre-rupture plaque harbor a hemodynamic environment characterized by higher WSS,higher pressure,higher velocity and high pressure difference across plaque may favoring the rupture of plaque.