Leaflet geometry

Of all the materials tested, including collagen, silicone rubber, PTFE, and polyurethane, PUs have turned out to have the best biocompatibility, durability, and thrombo-genic resistance. Polyurethane valve prostheses are either constructed from solvent-cast sheets of polyurethane, which are thermally formed into the correct leaflet geometry, or dip-cast valves, which use a stainless steel mold which is dipped into a polyurethane solution to produce the valve leaflets. It was found that the results for the dip-cast valve showed a more uniform distribution of mean axial velocity and Reynolds normal stress resulting from the more circular central orifice produced by the dip-cast leaflets [164]. 

Fig. 12 PVA-C heart valve prototype constructed using the arc subtending two straight lines geometry that integrates into a single part the three leaflets, stent, and sewing ring. Reprinted from [100] with permission. Copyright (2004) Elsevier...

On realizing the valve a geometry similar to the natural one has been chosen. It is, in fact, a tri-leaflet valve, where the leaflets have been assembled on a stent similar to those used for bioprostheses. This stent has been provided with three prongs connected to the basic ring with very wide fillets in order to limit the notch effects. The used thicknesses guarantee a sufficient softness to the whole structure, without endangering its strength. 

Geometry Number of DMPC molecules D(x 10- cmVs) Inner leaflet Outer leaflet... 

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