Analysis of the Effects of Viscoelastic Parameters and Wall Thickness on Carotid Wall Motion and Its Clinical Application

Abstract

Understanding the changes in arterial wall viscoelasticity during the progression of vascular disease is crucial. Nonetheless, there has been a lack of comprehensive investigation into the assessment of viscoelastic parameters and their impact on radial wall motion. To address this gap, we analyzed the radius waveform by solving the viscoelastic constitutive equations of the standard linear model (SLM) based on a thin-wall tube assumption. Additionally, a finite element method (FEM) was applied to simulate radial wall motion for thicker walls. The analytic solution showed that a well-balanced SLM model with the time constant (tau(epsilon)) values smaller than 0.05 s could effectively simulate the dynamic response of radial wall motion in a human carotid artery. FEM result showed that increasing wall thickness led to a decrease in the amplitude of the radius waveform, while its effect on phase lag was marginal. To evaluate the clinical relevance of arterial wall viscoelasticity, the viscoelastic parameters of the SLM were estimated from the pressure and diameter waveforms of each patient using an optimization technique. The 105 patients were categorized according to their cardiovascular disease risk status, and statistical comparisons were made for viscoelastic parameters across the different groups. The results revealed that the high-risk group exhibited significantly higher wall elasticity than the low-risk group (p < 0.03), while the intermediate-risk group demonstrated higher wall viscosity than the low-risk group (p < 0.01). Therefore, arterial wall elasticity holds potential as a significant indicator for distinguishing between low-risk and high-risk groups, whereas viscosity shows promise as a significant indicator for distinguishing between low-risk and intermediate-risk groups.