Prosthetic heart valves: waveform comparisons and average value disposition for pulsatile flow in vitro

With the development of the in vitro testing of heart valves, the standardization of the test methods becomes increasingly important and they should also be improved continuously. This paper discusses the problems of waveform comparison and average value dispositions. In the pulsatile model driven by pneumatics, the pressures before and after the valve, and the flow through it, are measured as three one-dimensional variates. The mean values are calculated according to the FDA and the ISO. A comparison and analysis of experimental waveforms indicate that, for basically the same ranges of pressures and flow rate, the flow curves of different types of valve are clearly different. The mean values and the waveforms in the time domain should be taken into consideration synthetically so that the pusatile characteristics of the valve can be more completely reflected. Using numerical filtering methods to treat the waveforms allows for better comparisons between the measured results taken from the different devices. By means of the constellation graphical method for treating mean values as multivariates, it is feasible to classify the valves and to judge their qualities under conditions of pulsatile flow.