The Effect of U-Shaped Patterns to Nonlinear Properties of Heart Rate Variability

Abstract

U-shaped patterns are acceleration-deceleration events characterized by high persistency of RR time intervals. Percentage contribution of U-shaped patterns to whole night-time series is small (in average 3%). However, the occurrence of U-shaped patterns affects to the properties of heart rate variability (HRV) significantly. The aim of this study is to evaluate its effect to nonlinear properties of HRV considering the ageing.Night-time 63 RR interval series from healthy subjects (26 males, 39 females, mean age: 40±14y) collected from the Institute of Cardiology and the Medical University of Gdansk were analysed. Nonlinear properties of HRV were described by using DFA, Multiscale Multifractal Analysis (MMA) and Sample entropy.We found significant differences of Sample entropy (p 2 (p 20, 33 pts) number of U-shaped patterns. In turn, we observed significant difference of DFA α 1 between the patients =39y (33 pts) (p<0.01). We also found the U-shaped patterns as the factor modulating the values of scaling exponents for wide range of scales.The effect of the U-shaped patterns on HRV appears to be much stronger than expected judging by their total length compared to the length of the signal.