Abstract: Background　The clinical data shows that the incidence of abdominal aortic aneurysm（AAA） is rising.A large number of studies have found that the cause of AAA is not only the internal cause of blood vessel biochemical properties，but also the external cause of blood hemodynamics.From the point of view of "stress-growth theory" of biomechanics，the abnormal hemodynamic environment will lead to the remodeling of pulmonary vascular structure，causing vascular diseases.Objective　To investigate the effect of internal hemodynamics on the generation and development of AAA in the case of abnormal deformation of the aortic blood vessels.Methods　The clinical CT image data of one case with healthy aortic vessel and two cases with typical AAA aortic vessel lesions in the Department of Neurology，Affiliated Hospital of Inner Mongolia University for Nationalities were collected in this article from 15 June 2016 to 31 July 2017.Three cases of CT data were reconstructed into a three-dimensional vascular structure model consistent with the real blood vessel using medical image three-dimensional reconstruction technology，and the numerical simulation was carried out using computational fluid dynamics software FLUENT 14.5.Based on the calculation results of hemodynamic characteristics in different vascular structure models with the same blood flow entrance velocity，the distribution of different blood wall shear stress，the distribution of blood flow after AAA in vascular and the secondary flow were compared，to explore the changes of hemodynamic characteristics in blood vessels after abnormal bending and distortion，and analyze the reason of hemodynamics caused by AAA.Results　On the premise of the same inlet velocity，and compared with the blood flow in the aorta of healthy person，the velocity and direction of blood flow decreased in the curved aortic arch of two AAA lesion models，and obvious circulation was found in the medial region of curved aortic arch.By calculating the distribution of secondary blood flow in the cross section of AAA model of arterial structure，it was found that the blood flow at the aortic arch appeared vortex flow，and the blood flow was normal after passing through the aortic arch，and the blood flow velocity was relatively low，the blood flow velocity at the bend of AAA increased locally.Compared with the tangential stress distribution of healthy blood vessel model，except for the large tangential stress at each outlet of blood vesselszthe tangential stress of aortic arch segment of human body was smaller，but the wall tangential stress of healthy blood vessel was slightly larger，and the distribution of tangential stress on the wall of blood vessel was more uniform in healthy human body.Conclusion　Compared with healthy human body，the abnormal bending and distortion of blood vessels of AAA are accompanied by secondary flow，and the phenomenon of secondary flow with high-speed and vortex can cause irreversible impact on the vessel wall，and thus causing the generation of AAA and increasing diameter of AAA gradually.

摘要： 背景　临床数据显示，腹主动脉瘤（AAA）的发病率呈逐年上升趋势，AAA的发病原因不但有血管自身生化性质的内因，也有血液血流动力学的外因。从生物力学“应力-生长理论”来看，异常的血流力学环境将会导致血管结构重建，致使血管疾病的产生。目的　探究主动脉血管发生异常形变时，其内部血流动力学特性对AAA的产生及发展的影响。方法　2016-06-15至2017-07-31采集内蒙古民族大学附属医院神经内科1例人体健康主动脉血管、2例典型AAA病变主动脉血管的临床CT图像数据。运用医学影像三维重建技术将3例CT图像数据重构出与真实血管一致的三维血管结构模型，并利用计算流体力学软件FLUENT 14.5进行数值模拟。基于相同血流入口速度在不同血管结构模型内血流动力学特性的计算结果，对比不同血管壁面切应力分布及发生AAA后的血管内血液流场及其二次流分布情况，探究血管发生异常弯曲、扭曲等形变后，其内部的血流动力学特性的变化，分析导致AAA产生的血流动力学原因。结果　相同入口速度前提下，与健康人体主动脉血管中血流状态相比，血流速度及方向在2例AAA病变模型中主动脉弓弯曲处血液流速降低，在弓部弯曲内侧区域发现明显环流。计算AAA患者动脉血管结构模型截面内血液二次流分布发现，血管主动脉弓处的血流出现涡旋流动，经过主动脉弓段后血流较为正常，且血流速度偏小，流经AAA弯曲处血流速度局部变大。与健康血管模型的切应力分布相比，除血管各出口位置的切应力较大外，人体主动脉弓段的切应力较小，但健康人体血管的壁面切应力稍大，且切应力在血管壁面分布较均匀。结论　与健康人体相比，AAA患者血管发生异常弯曲、扭曲等形变的同时伴有二次流的存在，且高速、涡旋的二次流现象会对血管壁造成不可缓解的冲击，从而导致AAA的产生，并使AAA的直径逐渐增大。

关键词: 腹主动脉瘤, 主动脉血管异常形变, 血流动力学, 预防