A system for studying spectral and temporal characteristics of acoustic cardiosignals

Summary form only given, as follows. The measurement of acoustic cardiosignals (noise and rhythm of the heart, acoustic signals of heart valves, etc.) is widely used for objective evaluation of the state of man's cardiovascular system under normal conditions and under increased loads alongside the study of cardiograms. However, the use of acoustic cardiosignals as temporal dependencies limits the possibilities of this method. This paper offers a description of the structure of the measuring system based on an IBM PC computer with the controller of the measuring equipment capable of working under remote control and in an independent mode. In addition to controlling functions, the computer is used to process the results of measurement. Acoustic cardiosignals are measured by a highly sensitive electret microphone which is located in the acoustic channel with a contact membrane at the receiving end. A specific feature of the measurements is the use of spectral and temporal analysis based on the Wigner-Ville transform for processing acoustograms. It offers maximum resolution in the frequency-time plane. This approach has been chosen due to significant non-stationarity of the processes under study. Alongside the temporal and correlation analysis of acoustograms, spectral and temporal analysis allows to expand essentially the research and diagnostic opportunities of the techniques using the specific features of acoustic cardiosignals. Our first results show some general patterns, such as the presence of rhythmic components, and some appreciable differences in the forms of spectrum and time distributions of the cardiosignals being measured. Significant irregularities related to sharp deviations of the pulse frequency from its average values have been observed. Apparently, a combined study of cardiograms and acoustograms will be the most informative method, since it will allow to establish the relationship between electrophysical and mechanical processes in the functioning of heart.