NORMAL RANGES OF HEART-RATE-VARIABILITY DURING INFANCY AND CHILDHOOD

Heart rate variability is a noninvasive index of the neural activity o f the heart. The present study examined heart sate variability indices in 210 infants and children aged 3 days to 14 years to obtain normal ranges for all age classes. Heart rate variability was measured by cal culating mean RR interval over the length of the analysis, mean RR int erval during quiet sleep, 5 time-domain (SDNN, SDNN-i, SDANN-i, r-MSSD , pNN50), and 4 frequency-domain (VLF, LF, HF, LF/HF ratio) indices. O ur data show a significant positive correlation between all indices an d the mean RR interval over the length of the analysis, except for the LF/HF ratio for which the correlation was binomial. A positive power correlation was also found between all parameters and age. The multipl e correlation analysis confirmed the independent effect of age and mea n RR interval on the heart rate variability. These data in a healthy p ediatric population confirm a progressive maturation of the autonomic nervous system during childhood and may be utilized to examine the eff ects of underlying disease processes or therapeutic interventions on c ardiac autonomic tone during infancy and childhood.