Passive stress-strain relation for the right ventricle in diastole

Wall thickness and medial line radii of an in vitro canine heart are measured. These data are assumed to be characteristic of the in vivo ventricles subject to zero pressure, and in the absence of filling. The myocardium is taken to be homogeneous, isotropic, non-linearly elastic, and incompressible. The right ventricular free wall is modeled as a circular arch of constant thickness, fixed at the interventricular groove. Circumferential stress is determined from thrust, and circumferential strain from displacement, both at the crown of the midwall. Our purpose was to obtain a stress-strain relationship without inertia and ventricular filling, termed passive. The passive circumferential stress-strain relation for the right ventricle in diastole is shown to be an exponential equation with two parameters. These parameters are related to the product of material constants of in vivo heart, and functions of right ventricular geometry in terms of the ratio of wall thickness to arch radius, and the terminal value of the central angle. Using mean values of observations, right and left ventricular passive curves are plotted over the same representative strain interval in an example from lowest diastolic pressure to the start of atrial contraction.