血管支架内表面正六边形微织构对血液流动特性的影响

Effect of Hexagonal Micro Texture on Blood Flow Characteristics of Vascular Stent

目的 探究具有不同面积占有率的正六边形凹坑微织构血管支架对血液流动特性的影响,探究微织构在抑制支架再狭窄中的作用。方法 在管状血管支架内表面设计具有不同面积占有率的正六边形凹坑微织构,采用Ansys有限元分析方法探究不同面积占有率微织构的存在对其腔内血液流速的影响。结果 带有微织构的支架腔体内血液流速大于无织构的支架腔体内血液流速。在整个心动周期内,心脏收缩时微织构面积占有率为31.9%的血管支架腔体内的主流区血液流速整体上最快;心脏舒张时微织构面积占有率为11.2%的血管支架腔体内的主流区血液流速最快。在峰值时微织构支架下的血液流动方向会产生径向跳动和扰动,血液流速产生了径向分量,在近壁面处血液出现了扰动和不稳定流动现象,微织构面积占有率越大,壁面产生扰动的血液越多。在平稳时刻,近壁面血液会产生回流,在无微织构支架下腔体内正常流动的血液与回流区血液形成了漩涡,面积占有率越大,形成的漩涡越明显。结论 血管支架内壁微织构的存在可以减小血液的黏附和流动时所受到的阻力,提高血液的流速,同时可以使近壁面处血液更好地混合,有利于改善血液的流动状态,降低再狭窄现象的发生概率,提高血管支架正常服务的寿命。

In recent years, there is a high incidence of cardiovascular and cerebrovascular diseases in China. The treatment methods mainly include surgery, drug therapy and interventional therapy. Surgical treatment is more traumatic, high risk, many adverse reactions of drug treatment, long treatment cycle, and the effect is not obvious. In contrast, interventional therapy has the advantages of safe operation, less surgical trauma, high success rate and less complications. At present, it has become the first choice for the treatment of cardiovascular and cerebrovascular diseases. The research report shows that the blood flow rate is the key influencing factor of restenosis after stent intervention in human body. If the blood flow rate is too slow, it is easy to deposit blood cells, lipids and other substances in the blood on the blood vessel wall, resulting in vascular blockage and restenosis over time. The work aims to study the effect of hexagonal micro pit texture vascular stents with different area occupancy rates on blood flow characteristics, and explore the role of micro texture in inhibiting stent restenosis. On the inner surface of tubular vascular stent, regular hexagonal micro pit textures with different area occupancy rates were designed, and the effect of micro textures with different area occupancy rates on the blood flow velocity in lumen was explored by Ansys finite element analysis method. The blood flow velocity in the lumen of the stent with micro texture was greater than that in the lumen of stent without micro texture. In a cardiac cycle, when the heart was contracted, the blood flow rate in the main flow zone of the micro-textured stent lumen with the occupancy rate of 31.9% was the fastest. When the heart was diastolic, the blood flow velocity in the main flow zone of the micro-textured stent lumen with the area occupancy rate of 11.2% was the fastest. At the peak, the blood flow direction in the stent without micro texture was parallel to the axis direction of the stent and the blood flow direction in the micro-textured stent produced radial runout and disturbance, the blood flow velocity produced radial component,and the blood near the wall showed disturbance and unstable flow. As the micro-textured area occupancy rate increased, more blood disturbed on the wall. At a steady condition, the blood near the wall flew back, and the blood flowing normally in the lumen of the stent without micro texture formed a vortex with the blood in the reflux area. The larger the area occupancy rate was, the more obvious the vortex was. The vortex changed the sliding friction between the blood and the wall into rolling friction, which reduced the resistance in the process of blood flow. The micro texture of the inner wall of the stent can reduce the resistance of blood adhesion and flow, improve the blood flow velocity, and make the blood near the wall better mixed, which is beneficial to improving the blood flow state, reducing the probability of restenosis and prolonging the normal service life of the stent.