PurposeThe understanding of the optimum function of the healthy aortic valve is essential in interpreting the effect of pathologies in the region, and in devising effective treatments to restore the physiological functions. Still, there is no consensus on the operating mechanism that regulates the valve opening and closing dynamics. The aim of this study is to develop a numerical model that can support a better comprehension of the valve function and serve as a reference to identify the changes produced by specific pathologies and treatments.MethodsA numerical model was developed and adapted to accurately replicate the conditions of a previous in vitro investigation into aortic valve dynamics, performed by means of particle image velocimetry (PIV). The resulting velocity fields of the two analyses were qualitatively and quantitatively compared to validate the numerical model. In order to simulate more physiological operating conditions, this was then modified to overcome the main limitations of the experimental setup, such as the presence of a supporting stent and the non-physiological properties of the fluid and vessels.ResultsThe velocity fields of the initial model resulted in good agreement with those obtained from the PIV, with similar flow structures and about 90% of the computed velocities after valve opening within the standard deviation of the equivalent velocity measurements of the in vitro model. Once the experimental limitations were removed from the model, the valve opening dynamics changed substantially, with the leaflets opening into the sinuses to a much greater extent, enlarging the effective orifice area by 11%, and reducing greatly the vortical structures previously observed in proximity of the Valsalva sinuses wall.ConclusionsThe study suggests a new operating mechanism for the healthy aortic valve leaflets considerably different from what reported in the literature to date and largely more efficient in terms of hydrodynamic performance. This work also confirms the crucial role that numerical approaches, complemented with experimental findings, can play in overcoming some of the limitations inherent in experimental techniques, supporting the full understanding of complex physiological phenomena.Electronic supplementary materialThe online version of this article (doi:10.1007/s13239-018-00391-1) contains supplementary material, which is available to authorized users.

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Transcatheter aortic valves are typically implanted inside the native (or failed bioprosthetic's) leaflets, permanently forcing the old leaflets open into a pseudo-cylindrical condition. Due to the passive nature of heart valves, the dynamics of the surrounding fluid environment is critical to their optimum performance. Following intervention, the haemodynamics of the region would ideally be returned to their healthy, physiological state, but major alterations are currently inevitable, such as increased peak flow velocity, the presence of stagnation regions, and increased haemolytic fluid environments. These leaflets reduce the volume of and restrict the flow into the Valsalva's sinuses, and minimise the development of vortices and associated flow structures, which would aid washout and valve closure. Despite these differences to the healthy condition, implantation of these devices offers much improved flow from that of a moderately stenotic valve, with reduced transvalvular systolic pressure drop, peak blood velocity, and shear stress, which normally outweighs the disadvantages highlighted above, especially for high risk patients.