Non-invasive measurement of local pulse pressure by pulse wave-based ultrasound manometry (PWUM)

Abstract

Central blood pressure (CBP) has been established as a relevant indicator of cardiovascular disease. Despite its significance, CBP remains particularly challenging to measure in standard clinical practice. The objective of this study is to introduce pulse wave-based ultrasound manometry (PWUM) as a simple-to-use, non-invasive ultrasound-based method for quantitative measurement of the central pulse pressure. Arterial wall displacements are estimated using radiofrequency ultrasound signals acquired at high frame rates and the pulse pressure waveform is estimated using both the distension waveform and the local pulse wave velocity. The method was tested on the abdominal aorta of 11 healthy subjects (age 35.7 ± 16 y.o.). PWUM pulse pressure measurements were compared to those obtained by radial applanation tonometry using a commercial system. The average intra-subject variability of the pulse pressure amplitude was found to be equal to 4.2 mmHg, demonstrating good reproducibility of the method. Excellent correlation was found between the waveforms obtained by PWUM and those obtained by tonometry in all subjects (0.94 < r < 0.98). A significant bias of 4.7 mmHg was found between PWUM and tonometry. PWUM is a highly translational method that can be easily integrated in clinical ultrasound imaging systems. It provides an estimate of the pulse pressure waveform at the imaged location, and may offer therefore the possibility to estimate the pulse pressure at different arterial sites. Future developments include the validation of the method against invasive estimates on patients, as well as its application to other large arteries.

Figure 1

Summary of the PWUM method for estimating the local arterial pulse pressure waveform: 1) B-mode image illustrating the central lines where the incremental distension will be measured, 2) Three consecutive frames illustrating the incremental displacement overlaid onto B-mode, the arrow depicting the onset of the wave, allowing to estimate the Pulse Wave Velocity (PWV)

Figure 2

(a) Example of waveforms obtained on the same subject at 6 different cardiac cycles; (b) the corresponding averaged waveform (red curve), as well as the standard deviation.

Figure 3

Example of pulse pressure waveforms obtained by both applanation tonometry and the PWUM method for two subjects (left column) and corresponding correlation plots (right column) (i) Subject 1 (28 y.o.) and (ii) Subject 2 (25 y.o.).

Figure 4

Tukey mean-difference plot representing the difference between the amplitude of the pulse pressure measured by PWUM and the one measured by tonometry, versus the average value between the two methods.