Suppression of shear-induced blood damage in cardiovascular systems

这个研究项目的重点是开发一种有吸引力的方法，通过研究微型、表面集成的被动流动控制元件（如涡流发生器、波纹、凹窝等），来减轻心血管硬件中高剪切应力的不利影响。血流剪切引起的血液损伤可导致血栓栓塞并发症，严重限制包括假体瓣膜、旁路泵和辅助装置在内的各种心血管硬件的性能。特别是，最近关于双小叶机械心脏瓣膜的研究强调了当血液成分受到非生生性血流动力学剪切应力时，血栓栓塞并发症的显著风险。目前，机械心脏瓣膜患者必须终身接受抗凝治疗，以预防血栓栓塞性并发症，但出血和其他继发性并发症的风险增加。减轻心血管硬件中高剪切应力的不利影响的一种有吸引力的方法是使用微型，表面集成的被动流动控制元件（例如，涡流发生器，波纹，凹窝等）来改变已知高剪切临界区域的内部速度分布，从而直接最小化这些应力。这些被动的流动控制元件在很多情况下都是受生物启发的，它们操纵和管理流动中的二次涡度浓度，从而增强横流混合、动量传递，改变局部速度和剪切应力分布。虽然初步工作证明了该方法的可行性，但要将该技术提升到一个新的水平，还需要进一步探索和优化各种被动流量控制配置。这项研究计划的更广泛的影响是开发一种新的设计范式或技术，适用于任何心血管硬件，基于这里开发的流量控制原理。所提出的工作将集中在一个简单的心血管试验台系统，该系统由一个理想的心脏瓣膜组成，配有被动涡发生器阵列和其他配置。不同的被动流量控制配置（刚性，柔性，几何形状）将被探索和优化。利用高分辨率锁相粒子图像测速技术（PIV），研究了被动涡发生器诱导的二次流（顺流涡量）对叶片闭合时瞬间湍流射流的影响。除了流体力学评估外，优化后的被动流量控制配置的促凝剂特性将被表征，并与没有流量控制的基线流量进行比较。与佐治亚理工学院最近的初步血液调查类似，拟议的血液研究将集中在血液凝固、血小板活化和溶血的测量上。这项研究将直接涉及佐治亚理工学院的研究生和本科生。特别强调将放在协作和测试配置的实际利益。该项目由热传输过程（TTP）计划、生物医学工程（BME）计划和流体动力学（FD）计划以及工程理事会（ENG）内的化学、生物工程、环境和运输系统（CBET）部门共同资助。

CBET-0828874YoganathanThis research program focuses on developing an attractive way to mitigate the adverse effects of high shear stress in cardiovascular hardware by investigating miniature, surface-integrated passive flow control elements (e.g., vortex generators, riblets, dimples, etc.). Blood damage caused by flow shear can cause thromboembolic complications that seriously limit the performance of a broad range of cardiovascular hardware including prosthetic valves, bypass pumps, and assist device. In particular, recent work with bileaflet mechanical heart valves has emphasized the significant risk of thromboembolic complications when blood elements are subjected to non-physiological hemodynamic shear stresses. Currently, patients with mechanical heart valves must undergo lifelong anti-coagulant therapy as a preventive measure against thromboembolic complications, but at an increased risk of hemorrhage and other secondary complications. An attractive way to mitigate the adverse effects of high shear stress in cardiovascular hardware is to use miniature, surface-integrated passive flow control elements (e.g., vortex generators, riblets, dimples, etc.) to alter the internal velocity distributions at known critical areas of high shear and thereby directly minimize these stresses. These passive flow control elements which in many cases have been bio-inspired, manipulate and manage secondary vorticity concentrations within the flow and thereby enhance cross stream mixing, momentum transfer, and alter local velocity and shear stress distributions. Although preliminary work demonstrates the viability of the approach, further exploration and optimization of various passive flow control configurations is necessary to take the technology to the next level. The broader impact of this research program is the development of a new design paradigm or technology, applicable to any cardiovascular hardware, based on the flow control principles developed here. The proposed work will focus on a simple cardiovascular test-bed system comprised of an idealized heart valve fitted with passive vortex generator arrays and other configurations. Different passive flow control configurations (rigid, flexible, geometries) will be explored and optimized. The effect of the secondary flow (streamwise vorticity) induced by the passive vortex generators on the momentary turbulent jet that forms when the leaflets close will be investigated in the pulsatile flow loop facility using highresolution, phase-locked particle image velocimetry (PIV). In addition to fluid mechanical evaluation, the pro-coagulant properties of optimized configurations of passive flow control configurations will be characterized and compared to a baseline flow in the absence of flow control. Similar to the recent preliminary blood investigations at Georgia Tech, the proposed blood studies will focus on measures of blood coagulation, platelet activation, and hemolysis. The study will directly involve participating Georgia Tech graduate and undergraduate students. Particular emphasis will be placed on collaboration and testing in configuration of practical interest. This project is jointly funded by the Thermal Transport Processes (TTP) Program, the Biomedical Engineering (BME) Program, and the Fluid Dynamics (FD) Program, all of the Chemical, Bioengineering, Environmental, and Transport Systems (CBET) Division within the Directorate for Engineering (ENG).