The contracted mammalian left ventricle functions similarly to an equivalent thick-walled sphere, allowing derivation of equations relating chamber internal volume to systolic pressure and energy.
Since, over a limited range, rubber has elastic properties similar to contracted cardiac muscle, a method for determining the elasticity constant of rubber left ventricle models has been developed and used to determine the elasticity constant of the contracted mammalian left ventricle. Serial determinations of left ventricular end-systolic pressure, enddiastolic volume, end-systolic volume, and stroke volume were carried out following increased blood volume and stepwise hemorrhages in rabbits, dogs, swine, horses, and cattle. The end-systolic pressure-volume relationship of the ventricle of these animals was found to be similar to that of rubber ventricle models, hemiprolate spheroids, and thick-walled spheres; evidence is presented that the contracted left ventricle, and rubber models of it, function as an equivalent thick-walled sphere having the same wall mass and internal volume. From the linear relationship between "average" wall stress and "average" circumference, equations are derived relating chamber internal volume and: systolic pressure, total potential energy, and energy dissipated in ejection of the stroke volume.
Holt et al. (Thu,) studied this question.