2023 年 37 巻 2 号 p. 96-104
The diastolic function of the ventricle is evaluated using the ventricular diastolic pressure-volume (P-V) relationship, and the P-V relationship is generally quantified by the stiffness or the stiffness constant. The P-V relationship of humans and other mammals is often normalized with the ventricular lumen volume to exclude the size effect on ventricular stiffness; however, in amphibians and reptiles which have trabecular ventricles, the ventricular mass is used for normalization instead of the ventricular lumen volume, because it is difficult to accurately define the ventricular lumen. In the present study, we investigated the ventricular diastolic P-V relationships of anurans of different sizes, and demonstrated both mathematically and experimentally that the stiffness parameters obtained directly from the P-V relationship were inversely proportional to the ventricular mass. We also demonstrated that the volume of the natural ventricular lumen was proportional to the ventricular mass. These combined results indicate that the stiffness parameters obtained directly from the P-V relationship are essentially dependent on the ventricular size. Normalization of V with ventricular mass attenuated the size effect, and we confirmed that this method is useful for comparing the diastolic function between the trabecular ventricles of different sizes when focusing on material properties.
