Key result
In an in vitro backward-facing step model, thrombus size exhibited asymptotic behavior over 10 to 90 minutes, with wall shear stress depending more on thrombus topography than size.
In vitro modeling demonstrates that thrombus growth in regions of flow separation reaches an asymptote, with wall shear stress driven primarily by thrombus topography.
Bench models quantify early thrombus stabilization in flow separation; leaves open in vivo validation for device design.
Thrombosis and thromboembolization remain large obstacles in the design of cardiovascular devices. In this study, the temporal behavior of thrombus size within a backward-facing step (BFS) model is investigated, as this geometry can mimic the flow separation which has been found to contribute to thrombosis in cardiac devices. Magnetic resonance imaging (MRI) is used to quantify thrombus size and collect topographic data of thrombi formed by circulating bovine blood through a BFS model for times ranging between 10 and 90 min at a constant upstream Reynolds number of 490. Thrombus height, length, exposed surface area, and volume are measured, and asymptotic behavior is observed for each as the blood circulation time is increased. Velocity patterns near, and wall shear stress (WSS) distributions on, the exposed thrombus surfaces are calculated using computational fluid dynamics (CFD). Both the mean and maximum WSS on the exposed thrombus surfaces are much more dependent on thrombus topography than thrombus size, and the best predictors for asymptotic thrombus length and volume are the reattachment length and volume of reversed flow, respectively, from the region of separated flow downstream of the BFS.
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Taylor et al. (2014) studied Thrombosis. Backward-facing step (BFS) model was evaluated on Thrombus size (height, length, exposed surface area, volume) and wall shear stress. In an in vitro backward-facing step model, thrombus size exhibited asymptotic behavior over 10 to 90 minutes, with wall shear stress depending more on thrombus topography than size.
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