Towards improved device design and clinical management: The thrombogenic effect of the fluid dynamics and material surface relationship

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Hastings, Susan M.
Ku, David N.
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Medical devices are burdened with complications of thrombosis and hemorrhage. The combined interaction of material surface, local hemodynamics (in particular shear rate), and large-scale thrombosis is poorly understood. First, basic science studies elucidated the relative importance of material surface and shear rate for large-scale bulk thrombus formation in an in vitro setup. The results from these studies were then used to develop a relative thrombogenicity ranking. It was found that relative material surface performance was modulated by shear rate, and that classical low and high shear thrombotic mechanisms were disrupted by artificial surfaces. Next, thrombogenicity was assessed in current blood-contacting devices and mechanistic understanding was discovered. In Extracorporeal Membrane Oxygenation (ECMO) circuits, it was revealed that the sudden expansions and contractions at connector junctions caused areas of super-low shear and potentiated thrombus in the entire device. In the Sorin Revolution centrifugal pump, the exposed stainless steel bearing surface was identified as a major potentiator of thrombosis. Then the clinical device thrombosis was simulated in vitro and validated against the clinical results, and the in vitro system was able to successfully replicate ECMO and centrifugal pump thrombosis. Finally, two novel devices were proposed to correct current thrombogenicity issues, and tested the prototypes were tested in vitro. The prototypes demonstrated superiority over current devices on the basis of bulk thrombus formation. The results in the context of material surface research and compared with other ranking studies and well as future directions for research are discussed.
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