engleski

Universal features in heartbeat dynamics

A physical system consists of numerous interacting units has a potential of displaying irregular and complex behaviour, but a remarkable thing is that it can also display a simple power-law behaviour. The "fractal concept" based on scale-invariance (in reality, nonexact invariance under scale transformation) can be successfully applied in the characterization of different physical systems. All of them have complex and irregular output of the measured time dependent parameters. They are driven by nonlinear interactions, and belong to the wide class of non-equilibrium phenomena. Examples are from turbulent flows and variation of atmospheric pressure to physiological systems, such as brain activity, and heartbeat (RR interval) variability. The article will discuss similarities and universal behaviour of fluctuation data, and their connection with anomaleous diffusion phenomena, where fractal scaling is not only a phenomenological description. Some results will show the applicability of nonlinear statistical methods for studying fluctuation patterns of RR intervals. Existence of universality classes predicted by the Random Matrix Theory (RMT), as well as scaling behaviour are examined for heartbeat RR interval time-series of healthy and diseased subjects. Particular interest is in the possibility of finding the method to distinguish healthy from diseased states, especially in the cases when changes in RR patterns (if exist) are not visible. This is the case with the coronary heart disease - stable angina pectoris. How changes in multifractal properties and changes in certain parameters in non-gaussian distributions, such as Brody and Berry-Robnik distribution, could provide a window into the possible complementary diagnostic methods, will be reported.

nonlinear interactions ; fluctuations ; heartbeat dynamics

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