The effect of mechanical property change of the viscoelastic tube on the characteristic of the arterial stiffness indexes. – Consideration based on numerical simulation –

Recently, Arterial Stiffness has attracted a great deal of attention as the predictor of the circulatory system condition. The Arterial Stiffness indexes (Pulse Wave Velocity: PWV, pulse wave shape index (AIx: Augmentation Index), Pulse Pressure: PP, Mean Arterial Pressure: MAP, etc.), seem to show the change of the static stiffness. However, the pulse wave has the periodic beating in vivo, it is considered that Arterial Stiffness index is influenced not only the static stiffness but also dynamic viscoelastic modulus or peripheral resistance. Accordingly, the analysis was carried out by using numerical simulation, to understand the effect of the difference of such mechanical property on the pulse wave propagation and the Arterial Stiffness indexes. A single cylindrical tube was constructed by the model of the systemic artery from central aorta to common iliac artery bifurcation. When the ideal beating of periodic pressure pulse wave were given at the input, pulse pressure conditions were calculated. The vascular elastic modulus, the viscoelastic modulus and peripheral resistance were changed independently. Following results were obtained. 1) By the increase in the vascular elastic and the viscoelastic modulus, the wave reflection from peripheral was increased, and then the PP and PWV increase. 2) By the increase in the peripheral resistance, the AIx and MAP increase although the PP does not change. From these results, following conclusions were obtained. 3) The change of PWV shows the change of vascular elasticity and viscoelasticity of the thick artery, and it similarly changes by the aging with the PP. 4) The AIx value gradually increase by the aging, similarly with the MAP.