Hans W. Liepmann Professor of Aeronautics and Medical Engineering California Institute of Technology, United States
Introduction:: During the rapid pressure changes of the cardiac cycle, the interaction between the left ventricle and the aortic valve generates high-frequency pressure signatures. These pressure fluctuations are commonly perceived as heart sounds, and are listened to using a stethoscope for cardiovascular auscultation. However, since these sounds are based on pressure, they propagate along the cardiovascular system in a typical pulse pressure waveform. This study aims to investigate a cuff-based method for non-invasive measurement of the pressure-sound waveform from clinical data in a catheter lab.
Materials and Methods:: This study data is from an invasive clinical trial with left heart catheterization of the left ventricular and simultaneous custom cuff-based measurement. The cuff system used in the study performs an oscillometric blood pressure measurement followed by three instances of pulse waveform acquisition with the inflate-and-hold method at DBP, MAP, and sSBP (SBP+35 mmHg). The cuff-based high-resolution pulse waveform from the sSBP hold is digitally filtered to extract the pressure-sound waveform. Filter optimization is performed to obtain a signal with two distinct oscillatory peaks representing the two heart sounds. The method is applied to left heart catheterization clinical data to measure the correlation between the pressure-sound waveform and the left ventricular contractile function. Contractile function is measured using the left ventricular pressure gradients of dPdt-max, maximal pressure gradient during isovolumetric contraction, and the negative dPdt-max, the maximal negative pressure gradient during isovolumetric relaxation. Correlations strengths are measured using the Pearson Correlation Coefficient (Pearson-R).
Results, Conclusions, and Discussions:: The analysis included 72 subject undergoing left heart catheterization and a simultaneous cuff pressure measurement. The method successfully extract the pressure-sound waveform from the sSBP hold consisting of a first peak, S1, and second peak, S2, corresponding to the forceful ejection of blood during the opening of the aortic valve and the closing of the aortic valve, respectively. The left heart catheterization data showed that pressure-sound peaks are highly correlated with left ventricular contractile function; the S1 amplitude had a strong linear positive correlation with the dPdt-max (Pearson-R=0.597, p< 0.001) and the S2 amplitude had a strong linear positive correlation with the negative dPdt-max (Pearson-R=0.500, p< 0.001). High-resolution cuff-based devices are capable of extraction pressure-sound waveforms generated by the left ventricle and aortic valve system. The waveforms contains valuable information for non-invasive interrogation of the left ventricle contractile function.
Acknowledgements (Optional): : The human subject data used in this study is from a clinical trial performed by Avicena LLC is entitled Assessment of the Vivio System for the Non-Invasive Estimation of Left Ventricular Diastolic Pressure as an Aid in the Diagnosis of Heart Failure (Unique Identifier: NCT05633004).
