Spatial energy balance within a structural model of the left ventricle.

A model describing the local instantaneous energetic needs within the left ventricle (LV) myocardium is presented. The model, which combines the myocardial oxygen consumption (MVO2) with the mechanical activity of the cardiac muscle, is based on the theory of cross bridge kinetics between the actin and myosin fibers within the sarcomere. The microscale relationship between the stress, stress development, strain rate and basal metabolism demand is incorporated into the LV model which describes the mechanical activities of different layers within the myocardium. The model shows a significant increase in the oxygen consumption in the endocardial layers as compared with the epicardial layers. Integrating the spatial and temporal oxygen consumption distribution within the myocardium yields the total myocardial oxygen consumption. The quantitative relationships between the heat rate, stress, contractility and external work and the MVO2 are in agreement with known data. The model thus offers a tool to assess the local instantaneous as well as the time averaged overall energy consumption, over a wide range of loading conditions of the LV.