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Platelet transport is further affected by nonuniform particulate concentration profiles.RBCs move toward the center of a vessel and platelets move toward the periphery, which is commonly called platelet margination.
The results indicate that observed thrombus growth rates are limited by platelet transport to the wall for shear rates up to 6000 s m/s).High shear rates exist near the stenosis apex, which is where rapid platelet accumulation can occur (5–11).The hemodynamics around a stenosis are pathophysiological with large changes in shear rate and the potential for flow separation, providing a rich, complex environment in which to compare a model with experimental thrombus growth.Some transport models have been used in an attempt to characterize RBC motion on a microscale (29–31), whereas others have modeled motion on a macroscale (32–34).Direct numerical simulations of particulate RBC and platelet motion are too computationally expensive for our study of large-scale thrombosis.Alternatively, the convection-diffusion equation can be used to model concentrated suspensions through the use of a potential function in the species flux constitutive equation, an enhanced diffusivity term, and a drift function for RBCs (24,35,36).
This approach allows for more exploration of relative shear effects with standard computational resources.
We have previously reported on the experimental creation of thrombus under high shear, near a stenosis, that grows to full occlusion and is consistent with clinical disease (11,38,39).
These thrombi grow very rapidly and are platelet-rich, with platelets comprised of ~80% of the thrombus.
Above 7000 s(-1), the thrombus growth rate is likely limited by binding kinetics (10(-4) m/s).
Thrombus growth computed from these rate-limiting steps match the thrombus location and occlusion times for experimental conditions if a lag time for platelet activation is included.
Platelet margination can create a large concentration of platelets near the surface of a vessel, reaching up to 17 times the average platelet concentration (26–28).