Spectral and spectral-temporal heart rate analysis in newborns

Spectral (in 3-min segments) and spectral-temporal (in 36-s windows with a 9-s step) analyses were carried out on the basis of cardiointerval recordings of newborns (full-term and preterm) during 24 h. It was found that each of the 3-min intervals of the 24-h cardiointerval recordings in the newborns had a unique spectrum; the spectra could be combined into several types. During 24 h, a spectrum with a marked LF component prevailed in the newborns. A spectrum with a peak in the HF region recorded in the newborns in the range from 0.4 to ∼1 Hz was an indicator of the rhythmic pattern of the variation of cardiointervals related to respiratory waves. Owing to the diversity of patterns of the spectral behavior of cardiointervals in a newborn during 24 h, no single short segment of the cardiointerval recording could serve as an unambiguous characteristic of the newborn’s physiological state. The actual heart rate variability pattern could be seen by means of the spectraltemporal analysis, visualizing the dynamics of conversion of one spectral type to another, i.e., the change of the dominant system of regulation.