Effect of Viscoelasticity of Vessel Walls on Pulse Wave

The pulse wave comes from the displacement of surface skin and is composed of incident and reflected waves. Since the properties of the reflected wave change considerably owing to the viscoelasticity of the vessel walls, the analysis of the reflected wave is considered to be useful for evaluating arterial stiffness; thereby, appropriate estimation of the incident wave is important for separating the pulse wave. Here, the incident wave is generated by a forward wave, which is the intravascular pressure caused by blood flow. In the former analysis, we assumed the blood vessel as an elastic tube and estimated the forward wave from the blood flow velocity waveform. In this study, we used a viscoelastic model to estimate a more appropriate forward wave. In this estimation, we used viscoelastic properties similar to those of bovine aorta, human aorta, or human artery. The estimated forward waves showed that the difference in the viscous properties of vessel walls causes minimal changes in the forward waves, which were also similar to that estimated using the elastic model. The result tells us that the elastic model is acceptable and useful for the estimation of forward wave, incident wave, and reflected wave, which enables the simple evaluation of the viscoelastic properties of vessel walls.