Simulation of damage in a porcine prosthetic heart valve

A model of a bioprosthetic porcine valve has been produced which simulates the non-linear elastic behaviour of the fixed tissue and the re-inforcement of the leaflets by collagen fibre bundles. The loading on the model is a s patially uniform but temporally varying distribution of pressure. Bending i s allowed in the tissue of the leaflets and is shown to be significant in d etermining the behaviour and failure modes of the leaflets. The simulation of the undamaged valve is validated against in vitro pulse duplicator studi es and a simple fluid-solid interaction simulation. Progressive damage is i ntroduced into three models of the valve at a location where tears have bee n commonly found in vivo. It was found that during the opening and closing of the valve the tip of the tears were subject to mode III or tearing displ acements, but that in the fully closed or diastolic state the tear tip was subject to mode I or opening displacements such that it would be expected t o propagate parallel to the line of attachment to the stent. The tear tip s tresses increased with the length of the tear so that the rate of tearing w ould be expected to increase with length.