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Mathematical analysis of left ventricular elastance with respect to afterload change during ejection phase
Shiro Kato1, Yukiko Himeno1, Akira Amano1
1Department of Bioinformatics, Ritsumeikan University, Kusatsu, Shiga, Japan.
Plos Computational Biology
|April 18, 2024
Summary
This study differentiates instantaneous and load-dependent left ventricular (LV) elastance using a hemodynamic model. Load-dependent elastance, unlike instantaneous elastance, is influenced by cardiac cell transient characteristics and force-velocity relations.
Area of Science:
- Cardiovascular Physiology
- Biomedical Engineering
- Computational Biology
Background:
- Left ventricular (LV) elastance, defined as the ratio of pressure (Plv) to volume (Vlv), offers insights into cardiac function.
- End-systolic elastance (Emax) is a recognized index of LV contractility, representing the slope of end-systolic pressure-volume points.
- The concept of elastance assumes LV elastance increases during ejection, peaking at end-systole.
Purpose of the Study:
- To define and differentiate 'instantaneous elastance' and 'load-dependent elastance' of the left ventricle.
- To investigate the relationship between instantaneous elastance and load-dependent elastance.
- To elucidate the underlying mechanisms governing these two elastance parameters using a computational model.
Main Methods:
- Development and utilization of a detailed hemodynamic model incorporating a ventricular myocyte contraction model.
- Simulation of cardiac function under varying loading conditions to generate pressure-volume data points.
- Analysis of model equations to determine the factors influencing instantaneous and load-dependent elastance.
Main Results:
- Isochronous pressure-volume points formed a linear relationship, with the slope (load-dependent elastance) slightly decreasing during ejection.
- Instantaneous elastance was found to be directly proportional to the ventricular myocyte's contraction force.
- Load-dependent elastance was determined by cardiac cell transient characteristics (velocity-dependent force drops) and the force-velocity relation.
Conclusions:
- Load-dependent elastance exhibits distinct behavior from instantaneous elastance during the ejection phase.
- The linear isochronous pressure-volume relationship arises from the interplay between cellular contraction dynamics and LV/aortic compliances.
- This study provides a mechanistic understanding of LV elastance variations based on cellular and system-level cardiac mechanics.
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