| Summary: | Given the poor durability of bioprosthetic heart valves and thrombogenicity of mechanical valves, recent attention has been directed towards synthetic leaflet valves. The work of this thesis forms part of a project to develop a tri-leaflet polyurethane heart valve prosthesis. Two aspects have been addressed: in vitro valve function and durability test methods, and fabrication techniques for polyurethane valves. Existing in vitro valve testing facilities, comprising a hydrodynamic function tester (pulse duplicator) and accelerated fatigue testers, have been upgraded. An improved data acquisition system combined with a computerised control system has been developed for the pulse duplicator. The new system allows valve function to be more efficiently and reliably assessed, and also provides a means for characterising the pulse duplicator and its transducers. Accelerated fatigue testing facilities have been similarly enhanced by the introduction of a computerised data acquisition system. In order to exploit the design potential offered by the use of a synthetic material, an integrated CAD/CAM system has been developed for producing sculptured valve formers. Such formers have been incorporated into injection moulding tools for tri-leaflet polyurethane valves. Polyurethane valves have been moulded, but to date not with sufficiently thin leaflets: the required leaflet thickness (< 150 gm) results in a mould cavity which presents an enormous resistance to flow in the injection moulding process. However, a finite element-based mathematical model has been used to simulate the flow of molten polyurethane into the mould cavity and initial results suggest that it should indeed be possible to injection mould a polyurethane valve and a practicable means of achieving this has been identified. The sculptured formers incorporated into the injection moulding tools have also been used to create dip moulded tri-leaflet polyurethane valves. These dip moulded valves, though difficult to produce consistently, function reasonably well in the pulse duplicator and accelerated fatigue tests are in progress.
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