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Autoregressive analysis of cardiac RR intervals in preterm and full-term infants
Insights
Autonomic nervous system maturation in infants shows decreasing sympathetic activity with age. Increased high-frequency fluctuations suggest developing respiratory-heart rate coordination.
Area of Science:
- Neonatal physiology
- Autonomic nervous system development
- Cardiorespiratory interactions
Background:
- The autonomic nervous system (ANS) regulates vital functions and its maturation is crucial for infant health.
- Understanding ANS development in premature and full-term infants provides insights into neurodevelopmental trajectories.
Purpose of the Study:
- To investigate the maturation of the autonomic nervous system in infants.
- To analyze changes in heart rate variability during sleep.
- To correlate these changes with conceptional and postnatal age.
Main Methods:
- Polygraphs recorded during sleep from 52 appropriate-for-dates infants (28-41 weeks conceptional age).
- Analysis of 104 RR interval time series using autoregressive (AR) and component analysis.
- Division of damping frequencies into low frequency (LF) and high frequency (HF) bands.
Main Results:
- Total power and LF power significantly decreased with increasing conceptional or postnatal age (P < 0.01).
- HF bio-informing activity and its damping time significantly increased (P < 0.001 and P < 0.01, respectively).
- LF power reduction suggests decreasing sympathetic activity with age.
Conclusions:
- Sympathetic nervous system activity diminishes as infants mature post-conceptionally and post-natally.
- Increased HF regularity and duration indicate developing cardiorespiratory coupling, possibly due to reciprocal respiratory-heart rate responses.
Abstract:
For the purpose of obtaining information on the maturation process of the autonomic nervous system in pre- and full-term infants, polygraphs were recorded during sleep from a total of 52 appropriate-for-dates infants at a conceptional age of 28-41 weeks. The 104 RR interval time series was calculated by autoregressive (AR) and component analysis. Histograms of damping frequencies obtained were divided into two frequency bands: low frequency fluctuations (LF) of less the 0.1 cycle/beat (c/b) and high frequency fluctuations (HF) of more than 0.15 c/b. Total power and LF power decreased with increases in the conceptional age or postnatal age at a significance level of 0.01, respectively. In addition, the HF amount of bio-informing activity increased (P < 0.001) and the damping time of HF also increased (P < 0.01). From these results, it was speculated that the activity of the sympathetic system decreases with increases in conceptional or postnatal age. It was also speculated that increased regularity and oscillatory duration in HF might be caused by the development of the reciprocal response of respiration to heart rate variation.