植入V形支架的降主动脉血流动力学观察

Observation of hemodynamics in human descending aorta after V-shaped stent implantation

目的观察植入V形支架并已经扩张稳定的人体降主动脉处的血流动力学指标,探讨支架植入的多少与远端支架处出现血管再狭窄的关系。方法获取1例动脉瘤患者覆膜V形支架植入术后复查的增强CT图像数据,以Dicom格式输入医学图像后处理软件,应用逆向工程方法三维重构主动脉血管和V形血管支架,在设定边界条件和初始条件的基础上,应用ANSYS模拟软件经多次迭代计算,获得血管壁面切应力、壁面振荡切应力和支架横截面血流速度矢量等相关血流动力学参数。结果由近及远,支架处的壁面切应力最大值逐渐降低,分别为3.56、3.26和2.48 Pa,而壁面振荡剪切指数平均值则相反,分别为0.002 140、0.005 677和0.010 852。在心动收缩峰值期(0.08 s),3个支架横截面处的血流速度均较大,方向多变并对支架有较大冲击,而在心动收缩末期和舒张期血流速度减缓,但与支架相接触处血流速度仍较高,并在舒张期出现明显的涡流。结论支架植入越多,降主动脉远端处支架的壁面切应力值越低,壁面振荡剪切指数值越高,且支架横截面的血流速度矢量越复杂,出现血管再狭窄的概率越大。

Objective To observe the hemodynamic parameters of the descending aorta with expanded V-shaped stent implantation , and to investigate the relationships between the stent number and vascular restenosis in the distal stents . Methods The enhanced CT image of the descending aorta with the V-shaped stents implanted was input into the medical image processing software with Dicom format , and the three-dimensional reconstruction model of aortic and stent was recon-structed by reverse engineering methods .On the basis of setting the boundary condition and initial condition , the vascular wall shear stress , wall oscillation shear stress , stent cross section flow velocity vector and other related hemodynamic pa-rameters were obtained with the application of ANSYS simulation software after several times of iterative calculation .Re-sults From the near to the distant , the wall shear stress values on the different positions were 3.56 Pa, 3.26Pa and 3.26 Pa, and the average values of oscillating shear index were 0.002 140, 0.005 677 and 0.010 852, respectively.In the sys-tolic peak period （0.08 s）, the blood flow velocities of the cross sections of three stents were larger with changeable direc -tions and had a great impact on the stent .While in the end-systolic and diastolic period , the flow velocity was slow down , but the flow velocity was still high in the contact point , and the eddy current was obvious in the diastolic phase .Conclu-sion With the stent increases , the wall shear stress value of the descending aorta decreases in the distal end but the wall oscillatory shear index value increases , meanwhile, the blood flow velocity vector of the stent cross section becomes more complex, and the risk of vascular restenosis increases .