Mathematical analysis of left ventricular elastance with respect to afterload change during ejection phase

by Shiro Kato, Yukiko Himeno, Akira Amano

Since the left ventricle (LV) has pressure (Plv) and volume (Vlv), we can define LV elastance from the ratio betweenPlv andVlv, termed as “instantaneous elastance.” On the other hand, end-systolic elastance (Emax) is known to be a good index of LV contractility, which is measured by the slope of several end-systolicPlv—Vlv points obtained by using different loads. The wordEmax originates from the assumption that LV elastance increases during the ejection phase and attains its maximum at the end-systole. From this concept, we can define another elastance determined by the slope of isochronousPlv—Vlv points, that isPlv—Vlv points at a certain time after the ejection onset time by using different loads. We refer to this elastance as “load-dependent elastance.”
To reveal the relation between these two elastances, we used a hemodynamic model that included a detailed ventricular myocyte contraction model. From the simulation results, we found that the isochronousPlv—Vlv points lay in one line and that the line slope corresponding to the load-dependent elastance slightly decreased during the ejection phase, which is quite different from the instantaneous elastance.
Subsequently, we analyzed the mechanism determining these elastances from the model equations. We found that instantaneous elastance is directly related to contraction force generated by the ventricular myocyte, but the load-dependent elastance is determined by tw...

Source: PLoS Computational Biology - April 18, 2024 Category: Biology Authors: Shiro Kato Source Type: research