Ejection Fraction and Espvr: A Study in the Mechanics of Left Ventricular Contraction

The end-systolic pressure-volume relation (ESPVR) is the relation between pressure Pm and volume Vm in the heart left ventricle when the myocardium reaches its maximum state of activation during contraction near end-systole. Relations between the ejection fraction (EF), parameters describing the ESPVR and the areas under the ESPVR are derived in this study for a linear model of the ESPVR. An important feature of the model is the inclusion of the active pressure generated by the myocardium during an ejecting contraction (also called isovolumic pressure Piso) in the mathematical expression of the linear ESPVR. Criteria that can help in understanding the problem of heart failure with normal or preserved ejection fraction (HFpEF) are discussed. Applications to clinical data published in the literature are presented, the applications show the consistency of the mathematical formalism used. When ratios of pressures are used, the calculation can be carried out with clinical data measured in a non-invasive way (the ratio of pressures can be calculated). This study shows that the EF is just one index of several indexes that can be derived from the ESPVR for the assessment of the ventricular function, and that using bivariate (or multivariate) analysis of data is superior to univariate analysis for the purpose of classification and segregation between different clinical groups.