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Heart rate (HR) and heart rate variability (HRV) in newborns is influenced by genetic determinants, gestational and postnatal age, and other variables. Premature infants have a reduced HRV. In neonatal HRV evaluated by spectral analysis, a dominant activity can be found in low frequency (LF) band (combined parasympathetic and sympathetic component). During the first postnatal days the activity in the high frequency (HF) band (parasympathetic component) rises, together with an increase in LF band and total HRV. Hypotrophy in newborn can cause less mature autonomic cardiac control with a higher contribution of sympathetic activity to HRV as demonstrated by sequence plot analysis. During quiet sleep (QS) in newborns HF oscillations increase - a phenomenon less expressed or missing in premature infants. In active sleep (AS), HRV is enhanced in contrast to reduced activity in HF band due to the rise of spectral activity in LF band. Comparison of the HR and HRV in newborns born by physiological vaginal delivery, without (VD) and with epidural anesthesia (EDA) and via sectio cesarea (SC) showed no significant differences in HR and in HRV time domain parameters. Analysis in the frequency domain revealed, that the lowest sympathetic activity in chronotropic cardiac chronotropic regulation is in the VD group. Different neonatal pathological states can be associated with a reduction of HRV and an improvement in the health conditions is followed by changes in HRV what can be use as a possible prognostic marker. Examination of heart rate variability in neonatology can provide information on the maturity of the cardiac chronotropic regulation in early postnatal life, on postnatal adaptation and in pathological conditions about the potential dysregulation of cardiac function in newborns, especially in preterm infants. [ABSTRACT FROM AUTHOR]

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This paper presents an overview of cardiac chronotropic regulation determinants in newborns, which are reflected in mean heart rate (HR) and heart rate variability (HRV). Heart rate and heart rate variability in newborns are determined by many factors. Heritability and maturation play major role. Factor of the maturation can be seen in HR and HRV differences between healthy full term and preterm newborns as well as in changes over early postnatal time. These parameters in newborns are influenced also by many other factors as gender, nutrition, sleep, breathing pattern/ventilation, etc. Autoregulation and extrinsic regulation of cardiac activity has its own specificities in newborns. Homeometric mechanism (depended on HR) is dominant and baroreflex sensitivity is reduced, mainly in premature newborns. Complex cardiac regulation can be studied and evaluated by cardiac reflexes. Examination of the reflexes in newborns is limited. Therefore, new approaches for the study of maturation cardiac control are developed taking into consideration all cardiac activity in newborns determinants. [ABSTRACT FROM AUTHOR]