Effects of stent geometry on local flow dynamics and resulting platelet deposition in an in vitro model.

Platelet deposition has been shown previously to depend on convective transport patterns, visualized by the instantaneous streamlines. Previous attempts to quantify hemodynamic studies of platelet deposition have been limited to 2D geometries. This study provides a physiologic assessment of the effects of stent geometry on platelet deposition by using actual 3D stents. Human blood with fluorescently labeled platelets was circulated through an in vitro system producing physiologic pulsatile flow in a compliant tube in which Bx Velocity, Wallstent and Aurora stents were implanted. Computational fluid dynamic models of the stents provided flow data to aid in explaining localized platelet deposition. Regions of constant flow separation proximal and distal to the strut exhibited very low platelet deposition. Platelet deposition was highest just downstream of flow stagnation regions due to convection towards the wall, then decreased with axial distance from the strut as flow streamlines became locally parallel to the wall. The nearly helically recirculating regions near the Bx Velocity stent connectors exhibited complex fluid dynamics with more platelet deposition, than the smaller separation regions. Localized platelet deposition was heavily dependent on flow convection, suggesting that arterial reaction to stents can be modulated in part by altering the hemodynamics associated with stent design.