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The use of LS-DYNA fluid-structure interaction to simulate fluid-driven deformation in the aortic valve

The physiology and anatomy of the human body is so complicated that viable simu- lations of even only parts of it require severe simplification. Accordingly, for our work on the mechanics of natural and replacement aortic heart valves, we have simplified into two sub-models the interactive complexity by which blood is ejected from the left heart ventricle to open and close the aortic valve. One model generates the distribu- tion of velocity across the aortic aperture, and this velocity field controls the fluid in- put into the second model, that of the aorta and valve. The three-dimensional model of the left ventricle is driven by applied wall displace- ments and it generates data for the spatially and time-varying blood velocity profile across the aortic aperture. This data then forms the loading conditions in another three-dimensional model, that of the aortic valve and its surrounding structures. Both models involve fluid-structure interaction and simulate the cardiac cycle as a dynamic event. Confidence in the models was obtained by comparison with data obtained in a pulse duplicator. The results show a circulatory flow being generated in the ventricle, a flow that produces a substantially axial motion through the aortic aperture. The aortic valve behaves in an essentially symmetric way under the action of this flow, so that the pressure difference across the leaflets is approximately uniform. These results support the use of spatially uniform but temporally variable pressure distribution across the leaflets in dry or structural models of aortic valves. Many valve design studies have relied upon such dry modelling, and so the evidence of the pre- sent work helps to underpin the value of previous dry work. Scientifically, the study is a major advance through its use of truly three-dimensional geometry, spatially non- uniform loading conditions for the valve leaflets and the successful modelling pro- gressive contact of the leaflets in a fluid environment.