The Study Of The Effect Of Hemodynamic Factors On Pathogenesis Of Intracranial Aneurysm

Objective:To simulate hemodynamic status of bent and bifurcation of intracranial artery as well as corresponding aneurysms,obtain parameters of hemodynamics,analyze the effect of hemodynamic factors on origin,growth and rupture of intracranial aneurysm,and provide theoretic support to clinical prophylaxis and treatment of aneurysm.Method:By the means of numeral simulation of computational fluid dynamics(CFD),three-dimensional model of bent and bifurcation of intracranial artery as well as 40 corresponding aneurysms were reconstructed with MIMICS10.0 and variety of hemodynamic parameters,such as velocity,pressure and wall shear stress,were obtained using ANSYS11.0.Characteristic of hemodynamic parameters in different location were compared and effects of hemodynamic factors on origin and growth of intracranial aneurysms were analyzed.The aneurysms were classified based on the geometry of parent artery. Characteristic of hemodynamics of different type aneurysms were described and its relationship to rupture of aneurysm was analyzed.Result:The CFD is a dependable simulation technique,which can provide various hemodynamic parameters.We found that the pressure of convex of internal carotid artery was statistical significantly higher than that of concavity(P =0.0001);the pressure in bifurcation of intracranial artery was statistical significantly higher than that of inlet artery and outlet artery(P＜0.05),however, the wall shear stress in bifurcation of intracranial artery was statistical significantly lower than that of inlet artery and outlet artery(P＜0.0001);and the areas of high pressure and wall shear stress in aneurysm were distributed at the distal part of aneurysm neck and its adjacent aneurysm wall.Based on the geometry of parent artery,the aneurysms were divided into four subtypes: sidewall aneurysm,sidewall aneurysm with branching vessel,endwall aneurysm, and fusiform aneurysm.We found that the pressure and wall shear stress in widernecked bent sidewall aneurysm were statistical significantly higher than those of smaller-necked straight sidewall aneurysm(F=349.72,P=0.000;F=34.46, P=0.000);the pressure and wall shear stress in sidewall aneurysm with a widercaliber draining vessel were statistical significantly higher than those of sidewall aneurysm with smaller-caliber draining vessel(F=107.87,P=0.000;18.20, P=0.001);the pressure in endwall aneurysm with wider angle between outlet artery and inlet artery was higher than that of endwall aneurysm with smaller angle between outlet artery and inlet artery(3.24,P=0.071);rupture rate of bent sidewall aneurysm was significantly higher than that of straight sidewall aneurysm(X~2=5.004,P=0.025);rupture rate of endwall aneurysm was higher than that of sidewall aneurysm(X~2=3.85,P=0.05);and all the aneurysms with mean pressure ratio between aneurysm and parent vessel exceeding 0.95 were rupture aneurysms.Conclusion:The CFD is a reliable simulation method to research hemodynamics of intracranial aneurysm nowadays;local high pressure in areas of bent and bifurcation of intracranial artery probably is mechanics foundation of origin of intracranial aneurysm;pressure and wall shear stress have together improve the growth of intracranial aneurysms;pathological factors might play a role in origin of intracranial aneurysms;the geometry of parent artery aneurysms markedly affects hemodynamic characteristic of intracranial aneurysm;and the aneurysms with relative higher pressure and/or higher wall shear stress are prone to rupture.