Is the time irreversibility of heart rate present even in newborns?

The aim of our research was to verify if the time irreversibility of heart rate oscillations exists even in the newborns. Multiscale irreversibility indices (Porta´s index P%, Guzik index G% and Ehlers index E) of the heart rate signals were computed in 20 healthy neonates. The presence of irreversibility and its origin in system nonlinearity was assessed by surrogate data analysis. The results were compared to irreversibility analysis of young adult heart rate signals. Surrogate data analysis revealed asymmetrical nature of the series present already in the neonatal age. Moreover Porta´s irreversibility index P% was significantly higher in newborns compared to adults indicating a shift in the sympatho-vagal balance in newborns towards sympathetic activity. The results of surrogate data analysis suggest an existence of the cardiovascular control system related time irreversibility in the majority of the recordings in both neonatal and adult groups.