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Development of heart rate variation over the first 6 months of life in normal infants
V L Schechtman1, R M Harper, K A Kluge
1Department of Anatomy and Cell Biology, UCLA School of Medicine 90024.
Insights
Heart rate variation in infants changes significantly during the first six months. Autonomic nervous system control of heart rate (HRV) develops, impacting different sleep states and HR patterns.
Area of Science:
- Pediatric cardiology
- Infant autonomic nervous system development
- Sleep physiology
Background:
- Heart rate variation (HRV) reflects autonomic nervous system (ANS) function.
- Understanding HRV development in infants is crucial for assessing cardiovascular health.
- Previous research has not fully detailed HRV changes across different sleep states in early infancy.
Purpose of the Study:
- To examine the developmental trajectory of HRV in three frequency ranges during sleep-waking states in healthy infants.
- To identify specific time periods and sleep states associated with significant alterations in HRV.
- To infer changes in autonomic control of heart rate during the first six months of life.
Main Methods:
- Longitudinal study of heart rate variation in normal infants over the first six months of life.
- Analysis of HRV in three frequency bands during various sleep-waking states.
- Assessment of respiratory sinus arrhythmia and lower frequency HRV bands.
Main Results:
- All three HRV types decreased from 1 week to 1 month of age.
- Respiratory sinus arrhythmia increased from 1 to 6 months, especially during quiet sleep.
- Lower frequency HRV increased from 1 to 3 months, then plateaued or reversed by 4 months.
- During rapid eye movement sleep, lower frequency HRV decreased from 3 to 6 months.
Conclusions:
- Autonomic control of heart rate undergoes significant alterations in early infancy.
- These changes affect specific HRV types and are state-dependent (e.g., sleep stages).
- A decrease in all HRV types at 1 month may suggest reduced vagal tone.
Abstract:
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.