The mathematical basis for wide discrepancies in previous time-varying elastance or compliance based models of the ventricle is presented. The fundamental difficulty of describing the mechanical properties of the ventricle with an elastance function that is set a priori , and the practical problem of the act of measurement changing the compliance magnitude are described. Elastance determined in this way is less restrictive than previous methods, but is still insufficient for description of the ventricle.
Results suggest abandoning elastance-based models of the heart.