Flow-Mediated Change in Viscoelastic Property of Radial Arterial Wall Measured by 22 MHz Ultrasound

Abstract

The endothelial dysfunction is considered to be an initial step in atherosclerosis. Additionally, it was reported that the smooth muscle, which constructs the media of the artery, changes its characteristics owing to atherosclerosis. Therefore, it is essential to develop a method of assessing the regional endothelial function and mechanical properties of the arterial wall. To evaluate the endothelial function, a conventional technique of measuring the transient change in the diameter of the brachial artery caused by flow-mediated dilation (FMD) after the release of avascularization is used. However, this method can not evaluate the mechanical properties of the wall. We previously developed a method for the simultaneous measurements of waveforms of radial strain and blood pressure in the radial artery. In this study, the viscoelasticity of the arterial wall was estimated from the measured stress-strain relationship using the least-squares method and the transient changes in the mechanical properties of the arterial wall ware revealed. From in vivo experimental results, the stress-strain relationship showed a hysteresis loop and viscoelasticity was estimated by the proposed method. The slope of the loop decreased owing to FMD, which resulted in the decrease in estimated elastic modulus. The increase in the area of the loop occurred after recirculation, which corresponds to the increase in the ratio of the loss modulus (depends on viscosity) to the elastic modulus when the Voigt model is assumed. In this study, the variance in estimates was evaluated by in vivo measurement for 10 min. The temporal decrease in static elasticity after recirculation due to FMD was much larger than the evaluated variance. These results show a potential of the proposed method for the thorough analysis of the transient change in viscoelasticity due to FMD.

Measurement of regional pulse wave velocity using very high frame rate ultrasound

“…In addition, methods for evaluating the elasticity and viscosity of the arterial wall have recently been developed [7][8][9][10][11][12][13]. For diagnosis of early-stage arteriosclerosis, it is useful to evaluate the elastic property of the arterial wall because arterial-wall elasticity changes with progression of arteriosclerosis [14].…”

Accurate measurement of elasticity of the radial artery wall considering changes in cross-sectional shape of artery caused by pushing pressure applied by ultrasound probe

“…Our group has focused on ultrasonic measurement of the relationship between the changes in the strain of the vessel wall and the blood pressure during one heartbeat to estimate the changes in the elastic and viscous moduli during FMD. [22][23][24][25] However, accurate viscoelasticity measurements were difficult because the measurement positions of the vessel diameter for the calculation of the strain and the pressure waveform were different.…”

Correction of change in propagation time delay of pulse wave during flow-mediated dilation in ultrasonic measurement of arterial wall viscoelasticity

“…For a more sensitive and detailed evaluation of the endothelial function and vessel wall mechanical property, a method of measuring the transient change in viscoelasticity during FMD was developed by our group. [8][9][10][11][12] However, in this method, stress (blood pressure) and strain (change in intima-media thickness) are measured in the radial artery in different arms. Moreover, the change in pulse wave velocity (PWV), 13,14) which is the velocity of the pressure wave caused by the contraction of the heart and propagating through the blood vessel, due to FMD has not been considered.…”