Modelling chorded prosthetic mitral valves using the immersed boundary method

The Immersed Boundary (IB) Method is an efficient method of modelling fluid structure interactions. However, it has two main limitations: ease of use and ability to model static loading. In this paper, the method is developed, so that it can efficiently and easily model any multileaflet elastic structure. The structure may include chordae, which attach to the leaflets and continue through the leaflet surfaces. In addition, an external surface pressure may be applied to the leaflets, thus enabling the deformations that arise under steady loads to be solved. This method is validated for a model of the native mitral valve under systolic loading and for a prosthetic aortic valve under static loading. It is then applied to a new chorded prosthetic mitral valve, housed in a cylindrical tube, subject to a physiological periodic fluid flow. Results are compared with those obtained by using the commercial package ANSYS as well as with experimental measurements. Qualitative agreements are obtained. There are some discrepancies due to the current IB method being unable to model bending and shear behaviour. In particular, the fibre structures of the new prosthetic valve model developed using the IB method may be prone to crimping. Further development of the IB method is necessary to include bending effects. This will improve the accuracy of both the dynamic and static analysis.