Study Of The Flutter Kinematics And Blood Flow Motion For Bioprosthetic Aortic Valves With Different Designs

OBJECTIVE: Improving bioprosthetic aortic valve (BAV) design is of paramount importance considering the increased number of aortic valve replacement procedures over the past decades. The design of such valves still needs further investigation to improve haemodynamic performance and to reduce detrimental flutter motion of leaflets that can lead to calcification and structural valve degeneration in time. For this reason, the effect of relevant shape parameters on leaflet kinematics and on flow features downstream of the valve is characterised in this study. METHODS: The approach considered to tackle the fluid-structure interaction (FSI) problem encompassing the simulation of the flow around a BAV and its leaflet kinematics is based on (i) a finite-element solver for the elastodynamics equation governing the valve mechanics, (ii) a high-order finite-difference solver for the incompressible Navier-Stokes equations governing the blood flow, (iii) a variational transfer for the strong coupling between fluid and structure. RESULTS: An emphasis has been put on the interplay of leaflet dynamics (more specifically, the observed flutter motion) and flow disturbances. In fact, the phenomenon of fluttering describes a relatively rapid oscillation of the leaflet mainly during peak systole. Depending on the designed leaflet shape, the simulated cases displayed very different motion, also named flutter modes, entailing the presence of different vortical patterns in the flow, levels of viscous shear stress close to the leaflets and von Mises stresses in the leaflets. The flutter modes characterised from the simulations have also been noted during in vitro experiments using high-speed cameras. CONCLUSIONS: This work brings new insights on the optimisation of the design of BAV leaflets from advanced numerical simulations of fluid-structure interaction problems. We anticipate that the developed approach and the findings may help to improve the design of BAV.