Computation of Nonlinear Parameters of Heart Rhythm Using Short Time ECG Segments

Abstract

We propose the method to compute the nonlinear parameters of heart rhythm (correlation dimensionD2and correlation entropyK2) using 5-minute ECG recordings preferred for screening of population. Conversion of RR intervals’ time series into continuous functionx(t)allows getting the new time series with different sampling ratedt. It has been shown that for alldt(250, 200, 125, and 100 ms) the cross-plots ofD2andK2against embedding dimensionmfor phase-space reconstruction start to level off atm=9. The sample sizeNat different sampling rates varied from 1200 atdt= 250 ms to 3000 atdt= 100 ms. Along with, theD2andK2means were not statistically different; that is, the sampling rate did not influence the results. We tested the feasibility of the method in two models: nonlinear heart rhythm dynamics in different states of autonomous nervous system and age-related characteristics of nonlinear parameters. According to the acquired data, the heart rhythm is more complex in childhood and adolescence with more influential parasympathetic influence against the background of elevated activity of sympathetic autonomous nervous system.