J. Bila, I. Bukovsky (Czech Republic), T. Oliveira, and J. Martins (Portugal)
Heart Rate Variability, Fuzzy Modelling, Cardiovascular System, Chaos, Correlation Dimension, Lyapunov Exponent,
This paper presents some results coming from continuous, non-linear modelling of heart rate (HR) complex behaviour caused by various neural control regimes while disorders inside the myocardium tissue are not present, and thus the possible vagal control capability to modify the complexity of HR variability is manifested. This model is believed to reveal more about importance of the delays of fast beat-by-beat vagal baroreflex control feedback influences and displays development of chaotic behaviour similar to the one observed in other, even much simpler, non-linear systems where the deterministic chaos develops such as through bifurcations, for example. The paper briefly describes features of the modelling method leading to complex behaviour of the cardiovascular system from periodic-like R-R diagrams to ones with high dimension of deterministic chaos. The correlation dimension and largest Lyapunov exponents were calculated for measured data and briefly compared to ones calculated for real cardiac disorder signals [12]. Distinct types of complex behaviour of the simulated HR due to the modified parameters of vagal multiple feedback were recorded. Parasympathetic neural control significantly appeared to make the system work in those distinct regimes. The origins of HRV are presented at the model, and their possible relevance to multi-attractor variability are mentioned.
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