RESUMO
In this paper an equipment is described for the loading of heart valve prostheses under physiological pressure conditions at a frequency of 10 Hz. The system consists essentially of two reservoirs between which a housing is mounted for holding the valve prosthesis. The reservoirs are partly filled with liquid. The physiological pressure variation across the valve is obtained by pressure control within the two reservoirs. A phase difference between the pressures in the two reservoirs compensates for the mass-inertia effects which normally occur at these high frequencies. The system without a valve has been analysed on the basis of simplified relationships between pressure and flow. The predicted values for the phase difference between the flow and the pressure curves within the valve housing, have been verified experimentally for various values of phase difference and amplitude ratios of the pressure variations within the reservoirs. The agreement between theory and experiment is fair. For the system with a valve the experimentally observed patterns closely resemble the theoretically predicted ones. From experiments with a Björk-Shiley ( 21ABP ) and a Hancock (242-A21) valve prosthesis it is concluded that the valves open and close completely and that the pressure and flow patterns around the valves mimic the essential features of the in-vivo signals.
