Crossbridge model compatible with the linear relation between left ventricular oxygen consumption and pressure-volume area

Ventricular pressure-volume area (PVA) is a specific area in the pressure-volume diagram, which represents the total mechanical energy generated by each contraction, consisting of stroke work and mechanical potential energy at end-systole. Animal experiments have shown that PVA is correlated linearly with the ventricular oxygen consumption (Vo2) per beat under a variety of loading conditions in a stable contractile state. The slope of the Vo2-PVA line has been shown to remain constant in different contractile states, implying a constant stoichiometry between Vo2 and PVA. As a first step to understand the nature of this Vo2-PVA relation, we devised a new crossbridge (CB) model to theoretically relate PVA with the total enthalpy change associated with the ATP hydrolysis for all CB cycles. One of the most important assumptions on which this model analysis depended was that the time-varying elasticity model could simulate the instantaneous pressure-volume relation. The result of this analysis implied that the empirical linear Vo2-PVA relation could be attributed to the energy balance between energy input and output of the chemomechanical transduction associated with CB cycles during a ventricular contraction.