Unexpected Course of Nonlinear Cardiac Interbeat Interval Dynamics during Childhood and Adolescence

Abstract

The fluctuations of the cardiac interbeat series contain rich information because they reflect variations of other functions on different time scales (e.g., respiration or blood pressure control). Nonlinear measures such as complexity and fractal scaling properties derived from 24 h heart rate dynamics of healthy subjects vary from childhood to old age. In this study, the age-related variations during childhood and adolescence were addressed. In particular, the cardiac interbeat interval series was quantified with respect to complexity and fractal scaling properties. The R-R interval series of 409 healthy children and adolescents (age range: 1 to 22 years, 220 females) was analyzed with respect to complexity (Approximate Entropy, ApEn) and fractal scaling properties on three time scales: long-term (slope β of the power spectrum, log power vs. log frequency, in the frequency range 10−4 to 10−2 Hz) intermediate-term (DFA, detrended fluctuation analysis, α2) and short-term (DFA α1). Unexpectedly, during age 7 to 13 years β and ApEn were higher compared to the age <7 years and age >13 years (β: −1.06 vs. −1.21; ApEn: 0.88 vs. 0.74). Hence, the heart rate dynamics were closer to a 1/f power law and most complex between 7 and 13 years. However, DFA α1 and α2 increased with progressing age similar to measures reflecting linear properties. In conclusion, the course of long-term fractal scaling properties and complexity of heart rate dynamics during childhood and adolescence indicates that these measures reflect complex changes possibly linked to hormonal changes during pre-puberty and puberty.

Symbolic patterns of heart rate dynamics reflect cardiac autonomic changes during childhood and adolescence

“…This monotonic increase with progressing age serves as a reference. Other linear time and frequency domain parameters show similar monotonic behavior (Cysarz et al, 2011).…”

“…due to attention-deficit disorder). However, previous results did not show any systematic changes in these subjects (Cysarz et al, 2011). Hence, all subjects were considered in this study.…”

“…These quantities show an increase with increasing age indicating that HRV is higher for adolescents than for pre-school children. Many other linear parameters in the time and frequency domain show similar age-related changes (Cysarz et al, 2011) and, hence, these parameters are all closely interdependent when focussing on age-related changes. The age-related occurrences of many binary pattern sets also show an increase or a decrease with increasing age.…”

“…ECG recordings from a previous study were re-analyzed (Cysarz et al, 2011). The recordings were obtained from 469 subjects.…”

“…R-R interval, increases with increasing age and, likewise, also linear measures such as the standard deviation of the R-R intervals and the very low frequency oscillations increase (Massin and von Bernuth, 1997;Massin et al, 2001;Silvetti et al, 2001). Measures derived from nonlinear dynamics, however, show unexpected variations during childhood and adolescence (Cysarz et al, 2011). E.g.…”