Abstract
Introduction: Thrombosis in LVADs can have fatal consequences either by causing device failure or by emboli causing stroke. Computational Fluid Dynamics (CFD) can predict flow fields in devices and various authors have created CFD based numerical models for clot formation. However, blood clots are not all the same; the concentrations of proteins and cells vary depending on the flow characteristics.
Methods: Eight steady state, convection-diffusion-reaction equations were solved including: von Willebrand factor (vWf) (collapsed, unfolded, fragmented), platelets (nonactivated, activated, receptor shed), and an example platelet agonist. Source terms for mechanical activation and receptor shedding from platelets used power law functions of shear stress and time. Rate constants for vWf unfolding and collapsing were dependent on the local flow type: rotating, shearing or extensional. Platelets attached to the walls according to a modified thrombus susceptibility potential. Blood flow was solved in Ansys Fluent with reaction equations implemented as User Defined Functions. Individual models were first compared with literature results from stenosis-like geometries. The model will be used to estimate clot type and location in the HeartMate II.
Results: Results for shear induced vWf unfolding were in good agreement with the literature in both symmetric and asymmetric stenosed flows. Qualitative agreement in regions of high platelet deposition was found. The relative numbers of platelets deposited in the different regions of the HeartMate II was similar to the relative numbers of thrombus formations.
Discussion: While the model still requires some tuning, it was able to predict the LVAD region with most thrombi.
Methods: Eight steady state, convection-diffusion-reaction equations were solved including: von Willebrand factor (vWf) (collapsed, unfolded, fragmented), platelets (nonactivated, activated, receptor shed), and an example platelet agonist. Source terms for mechanical activation and receptor shedding from platelets used power law functions of shear stress and time. Rate constants for vWf unfolding and collapsing were dependent on the local flow type: rotating, shearing or extensional. Platelets attached to the walls according to a modified thrombus susceptibility potential. Blood flow was solved in Ansys Fluent with reaction equations implemented as User Defined Functions. Individual models were first compared with literature results from stenosis-like geometries. The model will be used to estimate clot type and location in the HeartMate II.
Results: Results for shear induced vWf unfolding were in good agreement with the literature in both symmetric and asymmetric stenosed flows. Qualitative agreement in regions of high platelet deposition was found. The relative numbers of platelets deposited in the different regions of the HeartMate II was similar to the relative numbers of thrombus formations.
Discussion: While the model still requires some tuning, it was able to predict the LVAD region with most thrombi.
| Original language | English |
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| Publication status | Unpublished - 5 Sept 2024 |
| Event | 4th International Workshop on Flow-Induced Blood Damage in Rotating Systems - Technologiepark Warnemünde, Warnemünde, Germany Duration: 5 Sept 2024 → 6 Sept 2024 https://www.bdw.uni-rostock.de/ |
Workshop
| Workshop | 4th International Workshop on Flow-Induced Blood Damage in Rotating Systems |
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| Country/Territory | Germany |
| City | Warnemünde |
| Period | 5/09/24 → 6/09/24 |
| Internet address |
Funding
National Heart, Lung, and Blood Institute of the National Institute of Health under Award Number 1R01HL153538.