Analysis Of Computational Fluid Dynamics And Prediction On Frequent Site Of Rupture In Lenticulostriate Arteries

Hypertensive intracerebral hemorrhage(HICH)is a common subtype of stroke that is associated with high incidence,mortality and disability.ICH’s ictus frequently locates in the lenticulostriate arteries(LSAs)which are perforator arteries from the horizontal segment(M1)of middle cerebral artery(MCA).The LSAs supply the basal ganglia and the internal capsule.When the blood pressure elevates obviously,the LSAs don’t adapt to the raised blood pressure,which can result in rupture of LSAs.Nowadays,although there is a few literature available about physiopathologic mechanism of ICH,few researches about the analysis of LSA bleeding and frequent site of rupture exists regarding to our knowledge.Computational fluid dynamics(CFD)technology is accepted as an effective method to study cerebrovascular hemodynamics that is difficult to obtain through in vivo or in vitro experiments.Hence,the objective of this study is to provide a basic theory on the prognosis of HICH through analysing distributions of blood pressure and flow velocity of LSAs by means of finite-element analysis,and a flow chamber is used to simulate the effect of shear stress within LSAs on the vascular endothelial cells(ECs)in order to predict the position of aneurysms and artery damage.Firstly,2D model of LSAs was generated by GAMBIT2.3,including M1 segment of MCA(the diameter of 3mm,the length of 15mm),three levels of LSA branches(the diameter of 0.10 mm,0.14 mm,0.27 mm,respectively).There were 52,077 nodes and 95,282 cells by the paving algorithm for all triangular mesh generation.Secondly,this model was computed under pulsatile flow conditions using FLUENT6.3 pressure solver set by default with the first-order implicit coupled solution scheme based on steady and transient formulation.For simplicity,the vessel wall was designed to be rigid and no-slip.Navier-Stokes equation(N-S equation)was used to perform numerical calculation of incompressible Newton fluid(circulating blood: density ρ=1055 kg/m3,dynamics viscosity υ=3.3*10-4 Pa·s),and the data analysis was performed on TECPLOT.And then we designed a novel flow chamber which could be simulated the effect of shear stress within LSAs on ECs in vitro.In our study,the characteristics of hemodynamics were acquired,containing the blood flow velocity,velocity vector,and pressure distribution of LSAs.A positive correlation indicated significantly among the velocity and LSA diameter.The flow velocity was 45~30mm/s in Ⅱlevel branch of LSA,25~15mm/s in Ⅲ level branch,20~15mm/s in Ⅳ level branch closed to the measured same diameter arteriole blood flow velocity under normal physiological condition,corresponding to 0.44%,0.11% and 0.09% flow rate weighting,respectively.In addition,the origins(point 1,2,3)and bifurcations(point 4,6)LSAs showed turbulent and chaotic flow,this can result in vascular endothelial cells inflammatory responses,narrowing of the lumen and aneurysms.The significant magnitudes of pressure change and fluctuation concentrated on the terminal(point 10,11)of LSAs compared to the weighted parameter ω,that is to say,it forms the rupture-frequent site of the wall within the terminals when the blood pressure raised.The experiment in vitro demonstrated shear stress within LSAs(point 1,2,3,4,6,10,11)could lead to impairing ECs distinctly,increasing malondialdehyde concentrations and decreasing superoxide dismutase concentrations under hypertension,especially in the bifurcations of LSAs.These results showed that there were three vulnerable positions of rupture within LSAs,including the terminals(point 10,11),origins(point 1,2,3)and bifurcations(point 4,6).Interestingly the terminal of the LSAs rupture and bleed frequently,corresponding to the clinical summary statistics.And the original locations of LSAs are the frequent site of LSA aneurysms,cerebral haemorrhagic occurs when the aneurysms rupture.