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Open AccessArticle

Day and Night Changes of Cardiovascular Complexity: A Multi-Fractal Multi-Scale Analysis

1
IRCCS Fondazione Don Carlo Gnocchi, 20148 Milan, Italy
2
Italian Institute of Telemedicine, 21048 Solbiate Arno, Italy
3
Scientific Research Department of Cardiology, Science and Technology Park for Biomedicine, Sechenov First Moscow State Medical University, 119991 Moscow, Russia
4
Department of Medicine and Surgery, University of Milano-Bicocca, 20900 Monza, Italy
5
Istituto Auxologico Italiano, IRCCS, Department of Cardiovascular, Neural and Metabolic Sciences, S.Luca Hospital, 20149 Milan, Italy
*
Author to whom correspondence should be addressed.
Entropy 2020, 22(4), 462; https://doi.org/10.3390/e22040462
Received: 14 March 2020 / Revised: 15 April 2020 / Accepted: 16 April 2020 / Published: 18 April 2020
Recently, a multifractal-multiscale approach to detrended fluctuation analysis (DFA) was proposed to evaluate the cardiovascular fractal dynamics providing a surface of self-similarity coefficients α(q,τ), function of the scale τ, and moment order q. We hypothesize that this versatile DFA approach may reflect the cardiocirculatory adaptations in complexity and nonlinearity occurring during the day/night cycle. Our aim is, therefore, to quantify how α(q, τ) surfaces of cardiovascular series differ between daytime and night-time. We estimated α(q,τ) with −5 ≤ q ≤ 5 and 8 ≤ τ ≤ 2048 s for heart rate and blood pressure beat-to-beat series over periods of few hours during daytime wake and night-time sleep in 14 healthy participants. From the α(q,τ) surfaces, we estimated short-term (<16 s) and long-term (from 16 to 512 s) multifractal coefficients. Generating phase-shuffled surrogate series, we evaluated short-term and long-term indices of nonlinearity for each q. We found a long-term night/day modulation of α(q,τ) between 128 and 256 s affecting heart rate and blood pressure similarly, and multifractal short-term modulations at q < 0 for the heart rate and at q > 0 for the blood pressure. Consistent nonlinearity appeared at the shorter scales at night excluding q = 2. Long-term circadian modulations of the heart rate DFA were previously associated with the cardiac vulnerability period and our results may improve the risk stratification indicating the more relevant α(q,τ) area reflecting this rhythm. Furthermore, nonlinear components in the nocturnal α(q,τ) at q ≠ 2 suggest that DFA may effectively integrate the linear spectral information with complexity-domain information, possibly improving the monitoring of cardiac interventions and protocols of rehabilitation medicine. View Full-Text
Keywords: multifractality; multiscale complexity; detrended fluctuation analysis; heart rate; blood pressure; self-similarity multifractality; multiscale complexity; detrended fluctuation analysis; heart rate; blood pressure; self-similarity
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MDPI and ACS Style

Castiglioni, P.; Omboni, S.; Parati, G.; Faini, A. Day and Night Changes of Cardiovascular Complexity: A Multi-Fractal Multi-Scale Analysis. Entropy 2020, 22, 462.

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