Some Effects of Different Constitutive Laws on FSI Simulation for the Mitral Valve

This study examined how selecting different constitutive laws for mitral valve (MV) leaflets and chordae tendineae alters predicted MV dynamics under physiological fluid–structure interaction (FSI) loading. The authors compared three fiber-reinforced hyperelastic leaflet models (M1–M3) and two chordae models (linear vs exponential), first fitting parameters to experimental mechanical data and then simulating MV opening/closure using a hybrid immersed boundary / finite element (IB/FE) FSI framework implemented in IBAMR. Model outputs were compared using physiologically relevant dynamic metrics including peak transvalvular jet velocity, closure regurgitation volume, transvalvular flow rate, leaflet displacement, and orifice area at key time points (fully opened, just closed, fully loaded). While stress/strain fields along the fiber direction were broadly similar across leaflet models because each law was fit to the same mechanical dataset, the simulations showed meaningful differences in dynamic performance measures (e.g., closure regurgitation and orifice area) across constitutive choices. The analysis suggested that the M1 leaflet law provided the most favorable combination of large open orifice area with tight closure, and that using an exponential (nonlinear) chordae model reduced closure regurgitation compared with a linear chordae law. Overall, the paper highlights that constitutive-model selection can materially affect FSI-predicted valve function even when models fit static tissue tests similarly, and it provides guidance on model combinations better suited for simulating MV dynamics.