Clot growth under periodically fluctuating shear rate

To control the morphology of a clot formed on an artificial flow path in pulsatile blood flow, the hydrodynamic effect of periodically fluctuating shear rate on clot growth has been quantitatively investigated in vitro. Uniform shear rates were applied to a sample of beagle blood in the concave-convex cones system. These shear rates were sinusoidally fluctuated between a maximum and a minimum in one direction at frequencies between 0.1 and 0.6 Hz. Evaluation of clot growth was derived from a clot ratio, which was experimentally determined from the rate of increase of frictional torque between the two cones. The results show that clot growth is controlled so as not to occupy a large space when the minimum shear rate is higher than 100 s-1, or when the time of application of lower (< 100 s-1) shear rates is modified by the intermittent application of higher (> 500 s-1) shear rates as long as the frequency is less than 0.6 Hz.