Stanford B型主动脉夹层撕破口局部计算流体力学研究

The Computational Fluid Dynamics Study of Stanford Type B Aortic Dissection on Local Tear Area

目的:探索Stanford B型主动脉夹层局部血流动力学改变对主动脉夹层发生、发展以及临床预后评估的作用,为临床治疗方案选择提供理论依据。方法:通过CT扫描获取临床常见典型形态的Stanford B型主动脉夹层断层序列,重建出三维主动脉夹层计算流体力学分析模型,对主动脉夹层真假腔内血液流场进行数值模拟计算。结果:血液流经Stanford B型主动脉夹层撕破口时会对血管局部壁面产生冲击,造成动脉管壁局部压强升高,此种"冲击效应"不但会出现在近端夹层撕破口附近管腔壁面,也会出现在中间段及远端夹层撕破口附近,当入口血流压强升高时,夹层撕破口附近局部壁面压强差值也会增加。在心动周期内,Stanford B型主动脉夹层壁面剪切应力异常升高区也主要集中在撕破口区附近的动脉壁面上。结论:对于Stanford B型主动脉夹层而言,撕破口的位置相对于撕破口直径而言似乎更有临床意义。对B型夹层患者采用降低血压治疗,可减低局部动脉管壁上的壁面压强差值,但无法消除此壁面压强差,即主动脉夹层管壁上的局部危险区始终存在。此现象揭示主动脉夹层中远端撕破口也可能是造成夹层局部危险因素的原因,采用手术治疗方法封闭撕破口,以消除局部壁面压强增高区,降低破裂风险,可能是更理想的治疗方法。

Objective： To discuss the effect ofhemodynamic factors on the area near the tears of Stanford type B aortic dissection, and to assess the value of these factors in predicting the prognosis. Methods： The computational fluid dynamic simulations with patient-specific type B aortic dissection geometries were performed through the cardiac cycle. The blood flow pathlines, wall shear stress and static pressure on area near the tears were calculated and visualized. Results： The solution results indicated that there could be wall pressure and wall shear stress imbalance on the local aortic wall near the tears, which could be found not only near the proximal tear, but also near the middle and distal tears. The pressure differences on local area near the tears increased in accordance with the inlet pressure. Conclusion： The solution results demonstrated that there may be wall pressure and WSS imbalance on the local aortic wall in correspondence with the location of the tears, which may be a risk factor for the aortic rupture in future. Because the pure medications for lowering the blood pressure could not eliminate this risk factor, surgical procedures for sealing the tears may be more reasonable options for the therapeutic decision making.