Estimating the elastic modulus of non-atherosclerotic elastic arteries

Non-invasive measurements of the diameter and wall thickness of arteries in vivo, combined with recordings of pressure, permit the assessment of some mechanical aspects of arteries in vivo. However, arteries are anisotropic cylinders with complex elastic properties which can only be determined by a detailed evaluation. Many of the parameters required to calculate the anisotropic circumferential elastic modulus cannot be obtained in patients in vivo, or can be obtained only with difficulty.

Experiments were performed to assess the true anisotropic circumferential elastic modulus, and to find simpler methods of estimation.

One hundred and twenty dog carotid arteries were mounted in vitro and were extended to four lengths, 120, 130, 160 and 180% of the retracted length. The different lengths were applied in random order. The vessels were pressurized in steps while the longitudinal force and vessel diameter were measured. When a reproducible mechanical behavior was observed, the pressure, diameter and longitudinal force were recorded. These values were used to calculate the longitudinal elastic modulus, the circumferential-longitudinal Poisson's ratio and the true anisotropic circumferential elastic modulus with respect to the dimensions of the fully unloaded vessel. A number of simpler expressions were then evaluated for their value as approximations of the true anisotropic modulus.

Excellent estimates were obtained with a variety of expressions.

These methods may be useful for non-invasive assessments of the elastic properties of non-atherosclerotic arteries in patients.