FLOW EFFECTS ON VASCULAR STENT FAILURE

血管支架在临床上越来越多地用于各种血管疾病，但血栓形成和新生内膜增生继续损害这些器械的潜在效用。本提案中概述的研究基于以下假设：流体力学现象是血管支架临床失效的部分原因。本研究的总体目标是确定在急性实施阶段，流体力学如何与支架上的血小板沉积相关，以及如何改变支架设计以最大限度地降低流动相关再狭窄的风险。拟议研究的具体目标是： 测定圆柱形中的总血小板沉积量 使用体外流动装置的顺应性支架动脉模型 用人血作为工作流体。血小板沉积将是 通过放射性标记血小板的存在进行定量， 管壁三种不同的支架设计（两种市售 现有的设计和一个原型设计）将进行研究。 确定平板中血小板沉积的位置 使用荧光标记血小板的支架动脉模型， 共聚焦显微镜相同的三种支架设计将 研究了 量化三个区域中的流动分离和停滞程度 使用计算流体动力学（CFD）的不同支架设计 技术.由于存在脉动流布尔斯， 在流动分离中，定义了分离参数， 将以参数的方式变化。流动停滞的区域将是 通过存在持续低的所有剪切速率来鉴定。的 流动分离和停滞的程度将在统计上 与血小板沉积数据相比。 进一步阐明流动模式在血小板沉积中的作用， 通过实验和计算粒子 跟踪.将在支柱附近定量颗粒停留时间 在相同的三种支架设计中， 血小板沉积数据。 刺激CFD中新生内膜发育的进展 通过“填充”流动分离区域进行流动模拟。的 上述分离参数将适于定义 脉动流分离区域。由此产生的组织生长 模式将与现有的体内数据进行比较， 新生内膜发育模式。这项工作有望提供关于支架植入术机械方面的独特信息。这些信息将有助于开发下一代支架设计，其中动脉力学是主要考虑因素。

Vascular stents are being used clinically in increasing numbers for a variety of vascular disorders, but thrombosis and neointimal hyperplasia continue to compromise the potential utility of these devices. The research outlined in this proposal is based on the hypothesis that fluid mechanical phenomenon are, in part, responsible for clinical failures of vascular stents. The overall goals of this research are to determine how fluid mechanics may be related to platelet deposition on stents in the acute implementation stage, and how stent design can be changed to minimize the risk of flow-related restonosis. The specific aims of the proposed research are: Determine the amount of overall platelet deposition in cylindrical compliant stented artery models using an in vitro flow apparatus with human blood as the working fluid. Platelet deposition will be quantified by the present of radioactively labeled platelets on the tube wall. Three different stent designs (two commercially available designs and one prototype design) will be studied. Determine the localization of platelet deposition in a flate-plate stented artery model using fluorescent labeled platelets and confocal microscopy. The same three stent designs will be studied. Quantify the degree of flow separation and stagnation in the three different stent designs using computational fluid dynamics (CFD) techniques. Since the presence of pulsatile flow burs the definition of flow separation, a separation parameter has been defined and will be varied parametrically. Areas of flow stagnation will be identified by the presence of persistent low all shear rates. The extent of flow separation and stagnation will be statistically compared with the platelet deposition data. Further elucidate the role of flow patterns in platelet deposition in stents by performing experimental and computational particle tracking. Particle residence times will be quantified near the struts of the same three stent designs and statistically compared with the platelet deposition data. Stimulate the progression of neointimal development in the CFD flow simulations by "filling in" areas of flow separation. The separation parameter mention above will be adapted to define areas of pulsatile flow separation. The resulting tissue growth patterns will be compared with available in vivo data on neointimal development patterns. This work is expected to provide unique information on the mechanical aspects of stenting. This information will aid in developing the next generation of stent design in which arterial mechanics are a prime consideration.