Suppression of shear-induced blood damage in cardiovascular systems

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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).