Acquisition of diastolic heart sounds via a noninvasive method

Abstract

It has recently been shown that sounds caused by the turbulent flow in partiallyoccluded coronary arteries may be used for detecting the location of occlusions and isvaluable for an early, nomnvaslve diagnosis of coronary atherosclerosis.Unfortunately, it is difficult to isolate and analyze these sounds directly, since they arecorrupted with sounds having similar characteristics which originate from certaininternal sources, such as the valve sounds, or sounds from some external sources.In this thesis work a special instrumentation system for the acquisition ofdiastolic heart sounds is developed and physically realized. The system consists of twopassive sonic probes, two sound channels, anECG channel, various filters, a PersonalComputer equipped with an analog-to-digital converter board and a special dataacquisition software. To reduce amplifier saturation and cut-off problems, whichmight arise when the sensitive amplifiers of the system are subjected to momentarylarge inputs, like the S 1 and S2 valve sounds, a logarithmic amplification has beenused. One of the sound channels is used for monitoring the environmental noise.Using the information from this channel, the system software adaptively cancels out theeffects of external noise, allowing measurements in ordinary, non-sound-proof rooms.The ECG channel is used for placing time windows properly, during the diastolicphase of the heart, at which time background sounds are minimum and the soundscoming from the occluded coronary arteries are maximum.Keywords: Heart sounds, coronary atherosclerosis, sonic probes