New Results in Magnitude and Sign Correlations in Heartbeat Fluctuations for Healthy Persons and Congestive Heart Failure (CHF) Patients

摘要

Heartbeat fluctuations exhibit temporal structure with fractal and nonlinear featuresthat reflect changes in the neuroautonomic control. In this work we have used the detrendedfluctuation analysis (DFA) to analyze heartbeat (RR) intervals of 54 healthy subjects and 40patients with congestive heart failure during 24 hours; we separate time series for sleep andwake phases. We observe long-range correlations in time series of healthy persons and CHFpatients. However, the correlations for CHF patients are weaker than the correlations for healthypersons; this fact has been reported by Ashkenazy et al. [1] but with a smaller group of subjects.In time series of CHF patients there is a crossover, it means that the correlations for high andlow frequencies are different, but in time series of healthy persons there are not crossovers evenif they are sleeping. These crossovers are more pronounced for CHF patients in the sleep phase.We decompose the heartbeat interval time series into magnitude and sign series, we know thatthese kinds of signals can exhibit different time organization for the magnitude and sign and themagnitude series relates to nonlinear properties of the original time series, while the sign seriesrelates to the linear properties. Magnitude series are long-range correlated, while the sign seriesare anticorrelated. Newly, the correlations for healthy persons are different that the correlationsfor CHF patients both for magnitude and sign time series. In the paper of Ashkenazy et al. theyproposed the empirical relation: α_(singn)≈1/2( α_(original) α_(magnitude))for the short-range regime (highfrequencies), however, we have found a different relation that in our calculations is valid forshort and long-range regime: α_(sign)≈1/4( α_(original) magnitude)).