目的 提出一种基于理想几何的单向流固耦合计算方法,用于分析多层裸支架干预后主动脉夹层假腔内的血流动力学和假腔壁面应力等生物力学特征。 方法 根据假腔是否累及分支动脉将模型分为两类,建立多层裸支架作用下主动脉夹层的单向流固耦合数值仿真模型,进行血流动力学分析的同时考虑血流对壁面应力的影响。模拟不同手术策略干预下,术后假腔内的血流动力学和壁面应力状态特征,并对血栓形成前后的假腔壁面应力状态进行对比分析。 结果 忽略支架释放过程对假腔壁面应力的计算影响较小。仅用多层裸支架无法有效缩小假腔内的高流速、高壁面剪应力区域；仅用覆膜支架封堵近端入口,远端将维持高流速、高壁面剪应力区域；覆膜支架和多层裸支架联合使用会使假腔内出现最大范围的低流速和低剪应力区域,最大程度降低假腔内的压力和壁面应力。与有分支动脉模型相比,无分支动脉模型术后更易形成低流速、低壁面剪应力区域,然而,其术后假腔内血压更高。假腔内血栓的形成可以使血栓覆盖区域的壁面应力大幅下降。 结论 本文所提出的计算方法可以同时分析术后假腔内的血流动力学和壁面应力特征,为多层裸支架引发假腔血栓化以及主动脉再膨大的力学机理研究提供支撑。
Objective A one-way fluid-structure interaction (FSI) method based on an idealized aortic dissection model is proposed to analyze the hemodynamics and wall stress in the false lumen (FL) under the influence of multiple overlapping uncovered stents (MOUS). Methods Upon the establishment of the numerical model of one-way FSI of aortic dissection under the action of MOUS, the models were divided into two categories according to whether the model involved FL perfused branch artery. In the FSI model, the effect of blood flow on wall stress was considered, along with the hemodynamic analysis. The characteristics of hemodynamics and wall stress state in the post-operative scenarios were simulated under different surgical strategies. The wall stress state of the FL before and after thrombosis formation was also compared and analyzed. Results The release process of the stents has little influence on the simulation of the wall stress of the FL. The high velocity and high wall shear stress area in the FL cannot be reduced by using the MOUS alone. If only the proximal entry tear is blocked with a covered stent-graft, the distal end will maintain a region of high flow rate and high wall shear stress. Combination of covered stent-graft and MOUS will result in a region of low flow rate and low shear stress, as well as reduced wall pressure and wall stress in the FL Compared with the model with the FL perfused branch arteries, the model without it is more likely to form a region of low flow rate and low wall shear stress after surgery. However, the blood pressure in the FL was relatively higher. The formation of thrombus in the FL can greatly reduce the wall stress in the area covered by the thrombus. Conclusion The method proposed in this paper can simultaneously investigate the hemodynamics and wall stress characteristics of the FL, and provide support to study the mechanical mechanism behind the FL thrombolysis induced by MOUS and the post-operative aortic expansion.