Listening to heart sounds through the pressure waveform

Figures

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  Fig. 1. Method for sound pressure waveform extraction with brachial cuff. Step-by-step method for extracting the cardiovascular sound pressure waveform from a high-resolution brachial cuff device with inflate and hold capabilities. Part of the figure were generated with a modified picture from Servier Medical Art, provided by Servier, licensed under a Creative Commons Attribution 4.0 Unported License.

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  Fig. 2. Sound pressure waveforms from brachial cuff device extracted in a clinical study. (A) The three panels of the illustration show the sound pressure waveform extracted in the sSBP hold pressure for different individuals in the study. Catheter pressure signals (black) shown serve as a timing reference for the signals. (B) shows the cardiovascular signals timing intervals during a single cardiac cycle inclusive of cuff-based sound pressure waveform (red) and catheter aortic pressure (blue). The sound pressure waveform WP1 and WP2 peaks are labeled for reference. Acoustic pressure waveform has been time shifted using the calculated time delta to correct for wave propagation delay.

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  Fig. 3. Sound pressure signal comparison between simultaneous cuff and stethoscope. (A) Shows a ten-second segment of simultaneous stethoscope and sSBP hold sound pressure waveforms. (B) Shows the average waveform for the cuff and stethoscope highlighting the time shift between the WP1 and WP2 peaks. (C) The calculated beat-to-beat time delay between the cuff and stethoscope peaks showing a clear difference between the WP1 and WP2 time deltas. (D) shows the Instantaneous Frequency analysis for the WP1 and WP2 cuff sound pressure signal. (E) shows the Instantaneous Frequency analysis for the S1 and S2 stethoscope signal.

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  Fig. 4. Effect of the hold pressure on the sound pressure waveform morphology. Comparison between the pulse waveform and sound pressure waveform pairs for three holds: DBP (black), MAP (red), and sSBP (blue). Top row shows the characteristic pulse pressure waveforms, and the bottom row shows the extracted sound pressure waveforms. Each column represents a distinct individual from the clinical study.

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  Fig. 5. Comparison between cuff and catheter sound pressure waveforms. (A) shows a simultaneous cuff (red line) and catheter (blue line) sound pressure waveform segment from a subject in clinical study. Catheter pressure signal (black) is provided as a timing reference. (B) scatter plot comparing the WP1 and WP2 peak time intervals between the cuff and catheter signals. (C) shows the average time delays of cuff sound pressure signal compared to catheter sound pressure signal. (D) and (E) show the Instantaneous Frequency analysis for the sound pressure signal WP1 and WP2 in the cuff and catheter, respectively. (F) and (G) show scatter plots for the correlation of the height with the corrected Instantaneous Frequency of the WP1 and WP2, respectively.

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  Fig. 6. Correlation of Left Ventricular (LV) contractility with cuff-based sound pressure waveform parameters. (A) shows a segment of the simultaneous cardiac signals analyzed inclusive of the cuff-based sound pressure waveform (red) and the invasive catheter LV pressure (blue). (B) shows the scatter plots of the LV dPdt-max versus the WP1 parameter. (C) shows the scatter plot of the LV ndPdt-max versus the WP2 parameter. (D) shows the scatter plot of the LV p-RMS versus the cuff sound-pressure p-RMS.