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Shear-induced Thrombogenic Potential Of A Novel Tri-leaflet Mechanical Heart Valve Prosthesis Compared To A Bioprosthetic Valve And A Bi-leaflet Mechanical Valve: In-vitro Study Of Complex Flow Patterns And Turbulence
Leonardo Pietrasanta, Dominik Obrist.
University of Bern, Bern, Switzerland.

OBJECTIVE: Complex blood flow patterns and turbulence are principal determining factors for shear-induced thrombogenicity in prosthetic heart valves. The objective of this study is to analyse the thrombogenic potential of a novel tri-leaflet mechanical heart valve (TMHV) by comparing the flow field of the TMHV (mean flow velocities, wash-out patterns, turbulent shear stresses) to the flow fields of a bi-leaflet mechanical heart valve (BMHV) and a bioprosthetic heart valve (BHV).
METHODS: The tested valves (TMHV, BMHV, BHV) were mounted in a transparent phantom of an anatomically correct aortic root and integrated in a pulsatile flow loop reproducing physiological blood flow through the valves in aortic position. A multi-view imaging system for tomographic particle imaging velocimetry was used to measure the 3D flow field during a full pulse cycle. The data was analysed for mean flow, flow topology, and turbulent shear stresses.
RESULTS: The TMHV presents general flow patterns like in the BHV: A central systolic jet and retrograde flow along the aortic wall to enable the wash-out of the sinus portions. The wash-out in the TMHV is further enhanced by three side jets in the sinus portions. Peak turbulent shear stresses are of similar magnitude for all three valves. However, elevated turbulent shear stresses affect most of the blood flow behind the BMHV, whereas TMHV and BHV feature larger regions of laminar flow with low shear stresses and turbulent flow is concentrated in the shear layers along the edge of the central systolic jet.
CONCLUSIONS: The TMHV design with three leaflets in alignment with the sinus portions yields flow structures like in BHV. Together with the favourable sinus wash-out pattern and the lager regions of laminar flow with low shear stresses, the results suggest that the TMHV has a lower thrombogenic potential than a BHMV.


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