Document Detail

Development of baroreflex influences on heart rate variability in preterm infants.
MedLine Citation:
PMID:  10193925     Owner:  NLM     Status:  MEDLINE    
To investigate developmental changes in autonomic cardiovascular reflexes in preterm infants, we used autoregressive power spectral analysis to analyze the effect of upright tilting on heart rate variability in preterm infants. Twenty-eight infants were studied in a longitudinal fashion beginning at 28-32 weeks postconceptional age (postnatal age 1-5 weeks). Each week, heart rate variability in the supine position and after 45 degrees head-up tilt was analyzed by spectral analysis. With the initial study of each infant, there was no significant change in heart rate following head-up tilt compared with baseline (-0.5+/-0.9 bpm). However, linear regression analysis revealed that with increasing postnatal age, the change in heart rate in response to tilting became more positive (mean slope of regressions 0.45+/-0.12 bpm/week, P<0.005). The power spectral density of R-R interval variability in the low-(LF; 0.02-0.15 Hz) and high-(HF; 0.15-1.5 Hz) frequency ranges were obtained and the values normalized by dividing each component by the total power. For measurements obtained in the supine position, the LF/HF ratio progressively decreased with increasing postnatal age, indicating a maturational change in sympathovagal balance. We used the difference in the LF/HF ratio between tilt and the recumbent position as a measure of the change in autonomic input to the heart in response to unloading of the arterial baroreceptors. No significant change in these ratios were observed when infants were first studied between 28 and 32 weeks postconceptional age, suggesting that the cardiac baroreflex is poorly developed at this stage of development. However, with postnatal maturation, the LF component of the power spectrum became progressively larger with tilt relative to the basal state, such that the difference between LF/HF(tilt) and LF/HF(base) became progressively more positive (P <0.006). These findings suggest that in premature infants, cardiac baroreceptor reflexes become more functional with postnatal development.
J E Mazursky; C L Birkett; K A Bedell; S A Ben-Haim; J L Segar
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Early human development     Volume:  53     ISSN:  0378-3782     ISO Abbreviation:  Early Hum. Dev.     Publication Date:  1998 Nov 
Date Detail:
Created Date:  1999-05-27     Completed Date:  1999-05-27     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  7708381     Medline TA:  Early Hum Dev     Country:  IRELAND    
Other Details:
Languages:  eng     Pagination:  37-52     Citation Subset:  IM    
Department of Pediatrics, University of Iowa, Iowa City 52242, USA.
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MeSH Terms
Baroreflex / physiology*
Gestational Age
Heart / growth & development
Heart Rate / physiology*
Infant, Newborn
Infant, Premature / physiology*
Longitudinal Studies
Supine Position
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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