Left ventricular model parameters and cardiac rate variability

A recent functional model of the left ventricle characterizes the ventricle´s contractile state with parameters, rather than variables. The ventricle is treated as a pressure generator that is time and volume dependent. The heart´s complex dynamics develop from a single equation based on the formation and relaxation of crossbridge bonds within underlying heart muscle. This equation permits the calculation of ventricular elastance via E_v = ∂p_v/∂V_v. This heart model is defined independently from load properties, and ventricular elastance is dynamic and reflects changing numbers of crossbridge bonds. The model parameters were extracted from measured pressure and volume data from isolated canine hearts. The purpose of this paper is to present in some detail how to describe a particular canine left ventricle from measured data. The model is also extended to include heart rate variability, which arises naturally from the model structure. Computed results compare favorably with measurements both in this study and from the literature.