Fractional shortening of the left ventricle as analytically predicted in various species of widely differing body mass

The End-Systolic Diameter (ESD) versus End-Diastolic Diameter (EDD) relationship has been shown to offer a convenient framework to describe ventricular volumetric behavior. In most cases ESD is linearly correlated with EDD, both in an individual animal and for a group of different hearts. Many indices of ventricular function (such as Ejection Fraction, Pressure Volume Area, and Aortoventricular Coupling) directly depend on ESD. EDD or both. Since ESD and EDD change as a function of growth and age. it is of interest to study possible effects related to body size and age on clinically relevant indices such as the commonly used index of Fractional Shortening (FS). We analyzed ESD vs. EDD using data from our experiments, from dogs with heart disease and also in growing healthy foals. Subsequently, FS was predicted on the basis of an analytical expression. For three age groups in the dogs we found distinct curves. In the foals we found similar differences during early development. These results were confirmed by reanalysis of data collected from the literature. including man, dog and swine. We conclude that ESD vs. EDD is affected by growth and age, and that the consequences for FS can be analytically predicted. This implies that the index FS should be interpreted with caution, especially if age dependent effects are not properly incorporated.