Development of a cardiac acoustic mapping system.

The authors describe a cardiac acoustic mapping system designed to acquire, analyse, and display the amplitude distribution of a phonocardiogram (PCG) recorded from 22 sites on the thorax. A new PCG envelope detection approach, implemented by analogue circuits, enables simultaneous sampling of PCG envelopes from the 22 sites at a rate of 250 Hz/channel. A calibration procedure removes channel-to-channel gain variations, and a coherent averaging of each PCG envelope over several cardiac cycles improves the signal-to-noise ratio. Time congruent samples from the 22 averaged PCG envelopes are then interpolated in 2D to generate the isoamplitude maps. Preliminary results show that the acoustic maps can help locate the source of heart sounds and murmurs, and characterise their radiation and propagation patterns. Cardiac acoustic mapping opens up new avenues for the study of the propagation of heart sounds and murmurs through the heart-thorax acoustic system. This technique could contribute to improvements in the diagnosis of valvular dysfunctions.