Biomechanical experiments on excised myocardium: theoretical considerations.

Both the specific functional form of a constitutive relation and the particular material parameters must be determined from experiments. Constitutive formulations based on experimental data are valid, however, only when the experimentally measured stresses closely represent the actual distribution of stress in a specimen. In this paper, we present theoretical considerations to help experimentalists identify conditions under which biaxial data obtained from thin slabs of non-contracting myocardium satisfy the above criterion. In particular, we present both a general framework to investigate, and specific numerical examples to illustrate, the influence of certain distributions of muscle fibers, in-plane shearing strains and particular stretching protocols on the distribution of stress within biaxially tested myocardial specimens.