Heartbeat Dynamics is an Output of a Non-Chaotic Dynamical System driven by Physiological Noise

Heart rate variability (HRV) time series refers to the temporal fluctuations in R-R intervals and serve as an output of the cardiovascular system, which is known to produce complex and nonlinear dynamics. Although early studies suggested the presence of deterministic chaotic behavior in the cardiovascular system, the discovery of stochastic influences - hereinafter the physiological noise - challenged these conclusions. In this study, we propose a methodological framework for assessing whether noisy dynamical systems exhibit regular or chaotic behavior. We apply the proposed method to a total of 38 HRV series obtained from the publicly available Fantasia dataset, aiming to investigate whether aging modulates the regular/chaotic cardiac dynamics driven by physiological noise. Our results indicate that HRV series originate from a non-chaotic, i.e. regular, system influenced by dynamical noise. Young adults tend to show higher physiological noise driving heartbeat dynamics than elderly individuals.Clinical relevance: The characterization of the dynamical nature of HRV series is essential for improving diagnostic and prognostic strategies in neuro-cardiovascular medicine. Our findings support the view that the cardiovascular system operates under regular dynamics perturbed by physiological noise, which should be considered as a fundamental biomarker in neuroscientific research.