A Log-linearized Arterial Viscoelastic Index and Its Application to Carotid Ultrasonography

This paper proposes a method for qualitatively estimating the mechanical properties of arterial walls on a beat-to-beat basis through noninvasive measurement of continuous arterial pressure and arterial diameter. First, in order to describe the nonlinear relationships between arterial pressure waveforms and arterial diameter waveforms as well as the viscoelastic characteristics of arteries, we developed a second-order nonlinear model (called the log-linearized arterial viscoelastic model) to estimate the viscoelasticity of arterial walls. Next, to verify the validity of the proposed method, carotid viscoelastic indices were estimated based on arterial pressure waveforms measured using an ultrasonic device, and on arterial diameter waveforms measured using a noninvasive sphygmomanometer. The results showed that the proposed model could be used to accurately approximate the mechanical properties of arterial walls, and it was confirmed that the viscoelastic indices of arterial walls were proportional to age (stiffness: r=0.870; viscosity: r=0.668; and modified viscosity: r=-0.720). It was therefore concluded that the proposed model can be used to qualitatively evaluate arterial viscoelastic properties based on noninvasive measurement of arterial pressure and arterial diameter.