Measurement of Viscoelastic Properties of Arteries in the Living Dog

Abstract

Dynamic elastic moduli (E_dyn) and viscous moduli (ηω) of the arterial wall were obtained at a number of sites of the systemic vascular tree of living dogs anesthetized with pentobarbital. Constants were calculated using the first harmonics of pressure and diameter obtained from a Fourier analysis of simultaneously recorded pulse waves. The means and standard errors of E_dyn, in dynes cm^-2 x 10⁶, obtained at mean blood pressures ranging from 87 to 130 mm Hg and pulse frequencies from 1.1 to 2.8 cps were: 3.0±0.33 (9 midthoracic aortas), 9.8±1.2 (7 midabdominal aortas), 11.0 (4 iliac arteries), and 12.3±1.2 (11 femoral arteries). The viscous modulus was approximately 9% of E_dyn in the midthoracic aorta and approximately 12% of E_dyn in the abdominal and femoral arteries. Pulse wave velocities calculated from values of E_dyn and relative wall thickness by the Moens-Korteweg equation agreed with accepted values. A Fourier analysis of pressure and diameter waves was shown to be unsatisfactory for determining the frequency dependence of viscoelastic constants because of anomalous behavior of the viscoelastic parameters. In the midthoracic aorta this behavior may have been partly attributable to artefact; however, there was strong evidence that elsewhere nonlinear pressure and diameter relationships interfered with the accurate determination of the relatively small, higher-order harmonic components.