Bulgrin J R, Rubal B J, Thompson C R, Moody J M
Brooke Army Medical Center, San Antonio, TX.
Biomed Sci Instrum. 1993;29:465-72.
Heart sounds provide clinicians with valuable diagnostic and prognostic information. They are repetitive in nature, but reflect complex mechano-acoustical events which have been inadequately described by traditional digital signal processing methods. In this study, left ventricular and aortic intravascular phonocardiograms were obtained from six patients by catheter-mounted piezoelectric transducers. Phonocardiograms (PCGs) were bandpass filtered (50-500 Hz), digitized at 4kHz and analyzed by three separate techniques: (1) Short-Time Fourier Transform (STFT), (2) Fast Wavelet Transform (FWT), and (3) a pulse-counting time-domain method based on an Order Statistic (OS) filter. The resulting time-frequency distributions were employed to examine intra-patient and inter-patient acoustic variability. Results suggest that STFT and FWT provide comparable temporal and frequency resolution of cardiac acoustical events. However, the time-varying and multicomponent nature of heart sounds was poorly characterized by the OS technique employed in this study. This study suggests that improved localization of acoustic events during the cardiac cycle may prove useful in the development of automated auscultation devices.
心音为临床医生提供了有价值的诊断和预后信息。它们本质上具有重复性，但反映了复杂的机械声学事件，而传统数字信号处理方法对这些事件的描述并不充分。在本研究中，通过导管安装的压电换能器从6名患者身上获取了左心室和主动脉血管内心音图。心音图（PCG）经过带通滤波（50 - 500Hz），以4kHz进行数字化处理，并采用三种不同技术进行分析：（1）短时傅里叶变换（STFT），（2）快速小波变换（FWT），以及（3）基于顺序统计（OS）滤波器的脉冲计数时域方法。所得的时频分布用于检查患者内和患者间的声学变异性。结果表明，STFT和FWT在心脏声学事件的时间和频率分辨率方面具有可比性。然而，本研究中采用的OS技术对心音随时间变化和多成分的特性描述欠佳。这项研究表明，在心动周期中改善声学事件的定位可能对自动听诊设备的开发有用。
