654 - Preterm Infants Exhibit Altered Autonomic Balance During Sleep

Publication Number: 2637.654

Anna Shiraki, University of Geneva, Geneve, Geneve, Switzerland; Laura Lavezzo, University of Pisa, Pisa, Toscana, Italy; Hama Watanabe, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Gentaro Taga, The University of Tokyo, Bunkyo-ku, Tokyo, Japan; Enzo Pasquale Scilingo, University of Pisa, Pisa, Toscana, Italy; Mimma Nardelli, University of Pisa, Pisa, Toscana, Italy; Petra S. Huppi, University Hospital Geneva, Geneva, Geneve, Switzerland; Manuela O. Filippa, UNIVERSITY OF GENEVA, GENEVE, Geneve, Switzerland; Hiroyuki Kidokoro, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan

Background: Heart rate variability (HRV) is used to assess autonomic nervous system maturation, known to be more immature in preterm infants compared to full-term infants at term-equivalent age. However, how HRV is modulated by sleep states in newborns, and how this modulation is affected by prematurity is still under debate.

Objective: This study aimed to investigate differences in HRV parameters between active sleep (AS) and quiet sleep (QS), and between preterm and full-term infants. Because specific respiratory patterns such as apnea and periodic breathing (PB) can also influence HRV, epochs containing these events were excluded.

Design/Methods: We analyzed EEG polygraphy recordings from 37 preterm infants at term-equivalent age and 56 full-term infants, including ≥5 consecutive minutes of both AS and QS. Infants with severe brain injury or congenital abnormalities were excluded. Median (range) gestational age and postmenstrual age at recording were 32.1 (24.6-34.9) and 38.9 (37.0-41.1) weeks for preterm infants, and 38.7 (37.0-40.7) and 39.1 (37.6-41.3) weeks for full-term infants, respectively. Sleep-wake states were manually scored every 30 seconds using EEG, rapid eye movement, and respiratory data. Five-minute AS and QS segments without apnea of prematurity or PB were extracted. From the RR interval series extracted from the preprocessed ECG data, HRV parameters-mean heart rate (HR), standard deviation of RR intervals (SDNN), root mean square of successive RR interval differences (RMSSD), low-frequency (LF) and high-frequency (HF) power, and LF/HF ratio-were computed. Mean values per recording were compared between AS and QS in each group, and between preterm and full-term infants within the same sleep state.

Results: Postmenstrual age at recording was not different between preterm and full-term infants (P = 0.13). On average, preterm recordings contained 2 AS and 3 QS segments, and full-term recordings 4 of each. In both groups, HRV parameters were significantly higher during AS than QS, except RMSSD and HF power in full-term infants, which were higher during QS (Figs.1, 2). Compared to full-term infants, preterm infants showed significantly lower SDNN, RMSSD, LF and HF powers, and higher mean HR and LF/HF ratio during both sleep states (Fig.3).

Conclusion(s): When apneas and PB were excluded, autonomic activity was generally higher during AS than QS. However, full-term infants showed higher vagal activity during QS. The sympathovagal balance in preterm infants was skewed toward sympathetic dominance. These findings suggest immature sleep-related autonomic control in preterm infants.

Comparison of heart rate variability parameters between active sleep (AS) and quiet sleep (QS) in 37 preterm infants at term-equivalent age.
The Wilcoxon signed-rank test was applied to the standard deviation of RR intervals (SDNN), the root mean square of successive RR interval differences (RMSSD), low-frequency (LF) power, high-frequency (HF) power, and the LF/HF ratio, while the paired t-test was used for mean heart rate (HR). *P <0.05, **P <0.01, and ***P <0.001.

Comparison of heart rate variability parameters between active sleep (AS) and quiet sleep (QS) in 56 full-term infants.
The Wilcoxon signed-rank test was applied to the root mean square of successive RR interval differences (RMSSD), low-frequency (LF) power, high-frequency (HF) power, and the LF/HF ratio, while paired t-test was used for mean heart rate (HR) and standard deviation of RR intervals (SDNN). ***P <0.001.

Comparison of heart rate variability parameters between preterm (PT) and full-term (FT) infants within active sleep (AS) and quiet sleep (QS).
The Mann-Whitney test was applied to the standard deviation of RR intervals (SDNN) during QS, the root mean square of successive RR interval differences (RMSSD), low-frequency (LF) power, high-frequency (HF) power, and the LF/HF ratio, while the two-sample t-test was used for mean heart rate (HR) and SDNN during AS. *P <0.05, **P <0.01, and ***P <0.001.