Defining ventricular elastance

The mathematical reason 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. A new, isovolumic analytical model of the canine left ventricle yields ventricular elastance from the classic definition relating ventricular pressure and volume: E/sub /spl nu//=/spl part/p/sub /spl nu////spl part/V/sub /spl nu//. This new ventricle model is defined independently from circulation properties, allowing separation of source (ventricle) effects from load (circulation) effects. Elastance determined in this way is insensitive to ventricular preload and afterload.