Development of heart rate variation over the first 6 months of life in normal infants.
Development of heart rate variation in three frequency ranges was examined during sleep-walking states in normal infants over the first 6 mo of life. Extent of all three types of heart rate variation decreased from 1 wk to 1 mo of age. Extent of respiratory sinus arrhythmia increased from 1 mo to 6 mo during all sleep-waking states, with the increase most pronounced during quiet sleep. Variation in two bands of lower frequencies showed increases in extent from 1 to 3 mo, then a slowing or reversal of the increase between 3 and 4 mo of age. During rapid eye movement sleep, the two types of lower frequency heart rate variation decreased in extent from 3 through 6 mo of age. These results suggest that alterations in autonomic control of heart rate occur at several time periods over the first 6 mo of life and that these alterations may have an effect only on particular types of heart rate variation and only during particular sleep-waking states. The diminution of all three types of heart rate variation at 1 mo may indicate a reduction in vagal tone at this age.
Schechtman
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Department of Anatomy and Cell Biology, UCLA School of Medicine 90024.
Harper
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Kluge
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D000375:Aging / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D012119:Respiration / Q000502:physiology; D012890:Sleep / Q000502:physiology; D012895:Sleep, REM / Q000502:physiology; D014851:Wakefulness / Q000502:physiology