基于腹主动脉瘤数值模拟下的血流动力学分析

Analysis of hemodynamics based on numerical simulation of abdominal aortic aneurysm

目的探讨基于腹主动脉瘤(AAA)数值模拟条件下的血流动力学改变。方法收集昆明医科大学第四附属医院(云南大学附属医院)2019年6—9月体检的10例健康者的腹主动脉计算机体层血管成像(CTA)数据及10例AAA患者腔内修复术(EVAR)术前、术后的CTA数据。将其导入Mimics软件中,构建AAA三维数值模型,采用计算流体力学软件FLUENT对AAA三维数值模型进行流固耦合分析,得到AAA瘤腔内术前、术后10个心动周期内典型时刻的流场、壁面压力及切应力的分布图,分析其变化特点。结果术前AAA中,流线紊乱区域主要集中在瘤腔后下部位及主髂分叉处,主要以湍流和涡流为主,AAA的EVAR后血流流线在病变血管段呈层流趋势;血流流速自近心端向远心端呈递减趋势,瘤腔直径较大区域流速高于直径较小区域,与腹主动脉长轴成角大的一侧高于成角小的一侧,术后高流速主要集中于狭窄段;壁面压力整体表现为近心端大于远心端,在瘤腔的后下部位为高壁面压力的集中分布区,且在心室射血期末达最高值,术后壁面压力分布呈现由近心端向远心端递减的均匀分布趋势;高切应力分布于瘤颈、瘤腔后下部位、主髂分叉处及主髂成角较大的一侧,术后高切应力分布于主髂分叉部位。结论血流动力学参数在AAA瘤颈、瘤腔后下部位、主髂动脉分叉处等特殊部位出现明显改变,进一步证明血流动力学是AAA发生、进展的关键因素;关注瘤颈、瘤腔后下部位、主髂动脉分叉处等特殊部位的血流动力学改变,可优化EVAR的治疗方案。

Objective To investigate the hemodynamic changes based on numerical simulation of abdominal aortic aneurysm(AAA).Method The data of computed tomography angiography(CTA)of abdominal aorta were collected from 10 healthy subjects who underwent physical examination in the Fourth Affiliated Hospital of Kunming Medical University(Affiliated Hospital of Yunnan University)from June to September 2019.CTA data before and after endovascular aneurysm repair(EVAR)in 10 patients with AAA.The AAA three-dimensional numerical model was constructed by importing it into the Mimics software.The fluid structure coupling analysis of the AAA three-dimensional numerical model was carried out by using the computational fluid dynamics software FLUENT.The distribution maps of flow field,pressure and wall shear stress at typical times in 10 cardiac cycles before and after operation were obtained,and their variation characteristics were analyzed.Result In preoperative AAA,the flow line disorder areas were mainly concentrated in the posterior lower part of the tumor cavity and the main iliac bifurcation,mainly turbulence and eddy current.After AAA EVAR,the flow line showed a laminar flow trend in the diseased vascular segment.The flow velocity decreased from the proximal end to the distal end.The flow velocity in the area with large diameter was higher than that in the area with small diameter,and the side with large angle with the long axis of abdominal aorta was higher than that with small angle.The high flow velocity was mainly concentrated in the narrow segment after operation.The wall pressure showed that the proximal end was greater than the distal end,and there was a concentrated distribution area of high wall pressure in the posterior and inferior part of the tumor cavity.From the end of ventricular ejection to the highest value,the postoperative wall pressure distribution showed a uniform distribution trend of decreasing from the proximal end to the distal end;The high shear stress was distributed in the tumor neck,the posterior inferior part of the tumor cavity,the main iliac bifurcation and the side with a large angle of the main iliac.The high shear stress was distributed in the main iliac bifurcation after operation.Conclusion There were significant changes in hemodynamic parameters at the neck of AAA,the posterior inferior part of the tumor cavity and the bifurcation of the main iliac artery,which further proved that hemodynamics was the key factor in the occurrence and progress of AAA.To pay attention to the hemodynamic changes of tumor neck,posterior inferior part of tumor cavity and bifurcation of main iliac artery can optimize the treatment scheme of EVAR.