In vitro evaluation of prosthetic heart valves: anomalies and limitations

The in vitro evaluation of fifteen commercially available prosthetic heart valves is described. The group comprised both mechanical and bioprosthetic valves. The experimental studies were carried out in a steady flow circuit which included a flexible valve test section, the geometry of which was modelled on the aortic anatomy. The fluidic performance of the valves was examined over a range of flows and in particular, the phenomenon of "pressure recovery" distal to the valve was studied in depth. A number of theoretical parameters which might be used to define valve performance were evaluated but none was found to be ideal. The conclusions of the study emphasise the limitations of such in vitro testing and the danger of extrapolating such experimental data to the possible valve performance in vivo.