The pressure gradient across the endocardium

A mathematical formalism for the non-linear end-systolic pressure-volume relation (ESPVR) in the heart ventricles has the interesting feature that the peak active pressure generated by the myocardium (also called peak isovolumic pressure P
_isom
by physiologists) is included in the mathematical formalism describing the ESPVR. In this study we look at the ratio (P
_isom
- P
_m
)/P
_m
as an index to segregate between different clinical groups, this ratio can be calculated in a non-invasive way with the mathematical model used. Application to the left ventricle by using clinical data taken from the medical literature is given and discussed. Mathematical relations between the ejection fraction (EF) and the parameters describing the ESPVR are used in a way to get new insight into the problem of heart failure with normal or preserved ejection fraction (HFpEF).