Revisiting the Relevance of Platelet Margination in Arteries: a Computational Investigation*

Platelet margination (PM) refers to the migration of platelets toward the endothelial wall. Hence, it may influence platelet wall adhesion and thrombosis formation. PM has been experimentally observed in coronary-sized tubes (mm diameter) [1], [2] between 10 and 25 cm of tube length. These values surpass the typical axial locations of epicardial coronary arterial segments with atherosclerotic plaques [3]. This observation questions the need to consider PM in thrombosis simulations of the epicardial coronary arteries.

We investigated PM across vascular scales with 2D axisymmetric discrete particle transport (DPT) models: 1) A standard non-inertial drift-diffusion (DD) model [4], 2) a modified DD model accounting for shear and red blood cell concentration gradients [5], and 3) an inertial Maxey-Riley (MR) model [6]. Reynolds number (Re) and diameter ranged from 1 to 350 and 0.1 mm to 4 mm. We quantified PM as the percent displacement of particles from their initial radial position, as well as the normalized radial density of particles after 1 second of flow. 

All models had PM < 2% when diameter > 2 mm and Re > 20. The modified DD model had normalized near-wall platelet density of 6 for 0.1 mm vessels when Re < 4, whereas the standard model was 1.25. At these scales, the MR model led to center-of-vessel migration. All models had continuous, uniform platelet distributions when diameter > 2 mm. Our DPT results imply that PM may be negligible in coronary arteries. Future work will validate these results in 3D.