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Modeling the transient response to volume perturbations in the beating heart by the difference equation method
D Adler1, S D Nikolic, E H Sonnenblick
1Department of Biomedical Engineering, Hadassah University Hospital, Ein Kerem, Jerusalem, Israel.
The American Journal of Physiology
|April 1, 1994
Summary
This study models the heart's response to volume changes, finding that sustained mechanical alternans (SMA) are unlikely to be caused by preload and afterload variations. The discrete theoretical methods accurately predict experimental results in dogs.
Area of Science:
- Cardiovascular Physiology
- Computational Biology
- Biomedical Engineering
Background:
- The beating heart exhibits discrete dynamics, making discrete theoretical methods suitable for analysis.
- Understanding transient responses and sustained mechanical alternans (SMA) is crucial for cardiac health.
Purpose of the Study:
- To quantitatively understand the transient response to volume perturbation and SMA in the beating heart.
- To develop and validate a discrete theoretical model for cardiac mechanical behavior.
Main Methods:
- Utilized discrete theoretical methods and experimental studies in anesthetized dogs.
- Developed a three-stage model involving first- and second-order difference equations for stroke volume (SV) and aortic pressure (P).
- Investigated the influence of Frank-Starling mechanism (gamma) and afterload (lambda 1) on cardiac response.
Main Results:
- Model predicts different responses (non-oscillatory, oscillatory, SMA, chaotic) based on gamma and lambda 1 values.
- Experimental perturbations in dogs resulted in non-oscillatory (type 1) and oscillatory (type 2) decays.
- Model predictions were compatible with experimental findings in dogs, suggesting SMA is unlikely driven by preload/afterload variations.
Conclusions:
- Discrete models accurately capture cardiac response to volume perturbations.
- Experimental data supports model predictions, indicating preload and afterload variations are unlikely primary drivers of SMA.
- Further research may explore other mechanisms contributing to SMA.