Mechanical properties of arteries

Abstract

For the description of the mechanical properties of the arterial wall, a number of different models and mathematical approaches of varying complexity have been used. Most investigations based on the elastomeric approach have been related to the elastic properties of arteries, while relatively little is known about the arterial wall viscosity (η _w) and its dependence on circumferential wall stress (σ _t) and smooth muscle tone. For this reason we have examined these relationships on segments of the abdominal aorta, the carotid artery, and the tail artery of normotensive rats in vitro under the condition of strong smooth muscle activation induced by norepinephrine (NE), and during smooth muscle relaxation induced by papaverine (PAP).

Results:

1. For the abdominal aorta, the quotient of the dynamic (En) and the quasistatic elastic modulus (Est) increases from 1.5 to 2.1 under NE, and from 1.2 to 1.5 under PAP, for the carotid artery from 2.8 to 3.9 under NE, and from 1.3 to 1.4 under PAP, when σ _t increases from 10 to 120 kPa. For the tail artery, this quotient is 8.6 under NE and 1.9 under PAP in the low σ _t-range (5 to 60 kPa) and 12.1 under NE and 1.5 under PAP in the σ _t-range between 60 and 120 kPa.

2. For all three types of arteries, E_d and η _w increases with increasing σ _t. At a given σ _t, the values of E_d are virtually independent of frequency, while the values of η _w decrease markedly with increasing frequency.

3. The values of E_d and η _w, obtained under NE and PAP, are virtually identical for a given σ _t-range.