26:T49d,

Different rheological concepts and theoretical studies have been recently presented. using models of myocardial mechanics. Complex analysis of the mechanical behavior of the left ventricular wall have been developed in order to estimate the local stresses and deformations that occur during the heart cycle as well as the ventricular stroke volume and pressure.

Theoretical models have taken into account non-linear and viscoelastic passive properties of the myocardium tissue. when subjected to large deformations. through given strain energy functions or stress-strain relations. Different prolate spheroid geometries have been considered for such thick shell cardiac structure. During the active state of the contraction. the rheological behavior of the fibers has been described using different muscle models and relationships between fiber tension and strain. and activation degree.

A forthcoming approach for bridging the gap between the knowledge of the muscle fiber microrheological properties and the study of the mechanical behavior of the entire ventricle. consists in including anisotropic and inhomogeneous effects through fiber direction field.

27:T496,

In order to measure the flow-dynamical effect of arteriosclerotic changes of the vessel wall we determined volume elasticity E′ and modulus of elasticity ϰ of 53 human aortae in a static p-V-test as other authors did, too. The p-V-curves are normalized to the aortic basic volume V₀, so that we could determine the haemodynamic effect of arteriosclerosis immediately from E′ and ϰ.

Diameter, length, and, accordingly, the basic volume of the aorta without prestressing increase significantly in aortae with severe arteriosclerosis in comparison to those without sclerosis. The volume elasticity E′ as a function of the static aortic pressure has a minimum within physiological pressure range and changes into a linear function when arteriosclerosis increases. The modulus of elasticity of a normal aorta remains constant within a pressure range of 20 to 100 mm Hg and it shows a linear increase at higher pressure. The differences between V₀, E′ and ϰ of aortae with and without severe arteriosclerosis, however, are highly significant.

28:Tc2d,