Comparison Between Bench-Top and Computational Modelling of Cerebral Thromboembolism in Ventricular Assist Device...

Area of Science:

• Biomedical Engineering
• Cardiovascular Research
• Medical Device Technology

Background:

• Ventricular assist devices (VADs) are crucial for heart failure but are associated with high stroke rates (14-47%).
• Previous computational fluid dynamics (CFD) studies suggested optimizing VAD outflow graft (VAD-OG) implantation angles could mitigate stroke risk.

Purpose of the Study:

• To develop and validate an in-vitro model for assessing cerebral embolization in VAD-assisted circulation.
• To compare benchtop results with CFD predictions for VAD-OG implantation geometries.
• To quantify the reduction in embolization achieved by different VAD-OG implantation angles and a left carotid artery bypass-graft.

Main Methods:

• An in-vitro flow-loop model was constructed using a 3D-printed aortic bed and a continuous-flow pump, simulating VAD-assisted circulation.
• Spherical particles (2, 3.5, 5 mm) mimicking thrombi were injected into a mock VAD-OG, with flow conditions matching CFD Reynolds numbers.
• Particle embolization into simulated cerebral vessels was quantified using catch cans, and results were statistically compared to CFD predictions via Z-scores.

Main Results:

• The in-vitro model demonstrated strong agreement with CFD predictions across various VAD-OG implantation angles (Z-scores: -1.05 for perpendicular, 0.32 for intermediate, -0.52 for shallow).
• Implementing a left carotid artery bypass-graft significantly reduced embolization: 22.6% (perpendicular), 21.2% (intermediate), and 11.9% (shallow anastomosis).
• Shallow anastomosis VAD-OG implantation resulted in reduced aortic arch flow recirculation, aligning with steady-flow CFD computations.

Conclusions:

• Contemporary steady-flow CFD models are reliable for predicting VAD-induced cerebral embolization.
• In-vitro validation confirms that optimizing VAD-OG implantation, particularly with a shallow angle and bypass-graft, can effectively reduce stroke risk in VAD patients.