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Relation of beat-to-beat variability to heart rate in normal sleeping infants
Insights
Beat-to-beat heart rate variability (delta RR) in infants is positively correlated with instantaneous heart rate. These findings suggest delta RR should be corrected for RR intervals when assessing autonomic nervous system function.
Area of Science:
- Cardiovascular Physiology
- Infant Sleep Studies
- Autonomic Nervous System Function
Background:
- Heart rate variability (HRV) is a key indicator of autonomic nervous system (ANS) function.
- Understanding HRV in infants is crucial for assessing their physiological development.
- Previous research has not fully elucidated the relationship between beat-to-beat variability and instantaneous heart rate in sleeping infants.
Purpose of the Study:
- To investigate the relationship between beat-to-beat heart rate variability (delta RR) and instantaneous heart rate (RR intervals) in normal infants.
- To determine if this relationship differs between REM and quiet sleep states.
- To provide a basis for using delta RR as a reliable index of ANS integrity in infants.
Main Methods:
- Studied eight normal infants during the first four months of life.
- Monitored sleep states (REM or quiet) using neurophysiologic and behavioral criteria.
- Employed regression analyses to examine the correlation between delta RR and RR intervals.
Main Results:
- A significant positive correlation was found between delta RR and instantaneous heart rate (RR intervals) in both sleep states.
- Correlation coefficients ranged from 0.49 to 0.93.
- A linear approximation effectively described the delta RR to RR relationship, with similar slopes across sleep states and ages.
Conclusions:
- Beat-to-beat heart rate variability (delta RR) is positively correlated with instantaneous heart rate in sleeping infants.
- For accurate assessment of autonomic nervous system integrity, delta RR should be corrected for RR intervals.
- A physiological model explaining this correlation in cardiac output control is proposed.
Abstract:
The relationship of beat-to-beat heart rate variability (delta RR) and instantaneous heart rate was studied in eight normal infants while asleep during the first four months of life. The sleep state (REM or quiet) was determined using neurophysiologic and behavioral criteria. The results of regression analyses indicated that the delta RR values were positively correlated with the instantaneous heart rate (RR intervals). The correlation coefficient range was 0.49 to 0.92 in quiet sleep and 0.50 to 0.93 in REM sleep. Regression analyses supported a linear approximation of the delta RR to RR relation over the RR range investigated (400 to 520 msec). The median slope was 0.124 in REM and 0.117 in quiet sleep. The slopes of these linear functions were similar in both sleep states and at all ages. If beat-to-beat variability is to be used as an index of the integrity of the autonomic nervous system, these results suggest that delta RR be corrected for RR. A model is presented which relates the demonstrated positive correlation of delta RR to RR with the physiology of cardiac output control.