Feasibility of Estimation of Aortic Wave Intensity Using Non-invasive Pressure Recordings in the Absence of Flow Velocity in Man.

Alun D Hughes,Jamil Mayet,Chloe Park,Anenta Ramakrishnan,Nish Chaturvedi,Kim H Parker

doi:10.3389/fphys.2020.00550

Abstract

BackgroundWave intensity analysis provides valuable information on ventriculo-arterial function, hemodynamics, and energy transfer in the arterial circulation. Widespread use of wave intensity analysis is limited by the need for concurrent measurement of pressure and flow waveforms. We describe a method that can estimate wave intensity patterns using only non-invasive pressure waveforms (pWIA).MethodsRadial artery pressure and left ventricular outflow tract (LVOT) flow velocity waveforms were recorded in 12 participants in the Southall and Brent Revisited (SABRE) study. Pressure waveforms were analyzed using custom-written software to derive the excess pressure (Pxs) which was scaled to peak LVOT velocity and used to calculate wave intensity. These data were compared with wave intensity calculated using the measured LVOT flow velocity waveform. In a separate study, repeat measures of pWIA were performed on 34 individuals who attended two clinic visits at an interval of ≈1 month to assess reproducibility and reliability of the method.ResultsPxs waveforms were similar in shape to aortic flow velocity waveforms and the time of peak Pxs and peak aortic velocity agreed closely. Wave intensity estimated using pWIA showed acceptable agreement with estimates using LVOT velocity tracings and estimates of wave intensity were similar to values reported previously in the literature. The method showed fair to good reproducibility for most parameters.ConclusionThe Pxs is a surrogate of LVOT flow velocity which, when appropriately scaled, allows estimation of aortic wave intensity with acceptable reproducibility. This may enable wider application of wave intensity analysis to large studies.

Highlights

Blood pressure (BP) results almost entirely from waves generated by the heart; the intensity of these arterial waves is an important measure of ventriculo-arterial function and their interaction
Given that wave intensity is the product of the derivatives of pressure and flow velocity this suggests that it should be possible to estimate wave intensity patterns using the measured pressure waveform and Pxs derived from reservoir analysis
Bland Altman plots indicating the agreement between peak wave intensities for conventional WIA and pressure-only wave intensity analysis (pWIA) are shown in Figure 3 [mean difference Wf1 = −15 (LOA −106, 75) W/m2 × 104/cycle2, rho = 0.83; Wb = −49 (LOA −29, 19) W/m2 × 104/cycle2, rho = 0.42; −44 (LOA −13, 44) W/m2 × 104/cycle2, rho = 0.73]

Summary

Introduction

Blood pressure (BP) results almost entirely from waves generated by the heart; the intensity of these arterial waves is an important measure of ventriculo-arterial function and their interaction. While wave intensity analysis is not the only method to characterize waves in the circulation (Westerhof et al, 2005; Caro et al, 2012), it has proved an increasingly valuable approach to understanding hemodynamics and wave propagation in the circulation, since it quantifies the intensity and energy carried by forward and backward-traveling waves, along with their timing (Parker and Jones, 1990; MacRae et al, 1997; Parker, 2009; Broyd et al, 2015; Su et al, 2017) This has prognostic value: wave reflection has been reported to predict cardiovascular events independently of other cardiovascular risk factors (Manisty et al, 2010) and more recently, elevated wave intensity has been independently associated with greater decline in cognitive function from mid- to late life (Chiesa et al, 2019). We describe a method that can estimate wave intensity patterns using only non-invasive pressure waveforms (pWIA)

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Conclusion