title: The PR interval-fetal heart rate relationship during repetitive umbilical cord occlusions in immature fetal sheep.
abstract: OBJECTIVE
  To evaluate the relationship of the PR interval and fetal heart rate during repetitive umbilical cord occlusions in immature sheep fetuses.
  
  
  METHODS
  In seven chronically cannulated immature sheep fetuses [gestational age 90.6 days (mean)], we analyzed continuous fetal electrocardiogram recordings during repetitive cord occlusions for 2 out of every 5 min until fetal mean arterial pressure dropped to 50% of baseline value. PR interval-fetal heart rate correlation coefficients (Pearson) was measured on consecutive blocks of 2.5 min. R-values of the baseline and the repetitive occlusion period were compared by Fisher's exact test.
  
  
  RESULTS
  Repetitive cord occlusions resulted in acidosis and hypotension. Two fetuses died at the end of the repetitive occlusion period. Four out of seven fetuses showed a significant change from a negative relationship between the PR interval and fetal heart rate during baseline to a predominantly positive relationship during the repetitive occlusion period.
  
  
  CONCLUSIONS
  In immature fetal sheep, a change from a negative relationship between the PR interval and fetal heart rate to a predominantly positive relationship between the PR interval and fetal heart rate was observed in four out of seven fetuses following the initiation of repetitive umbilical cord occlusions.
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital Maastricht, The Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Keunen
authors.forename: W J
authors.initials: WJ
authors.lastname: van Wijngaarden
authors.forename: D S
authors.initials: DS
authors.lastname: Sahota
authors.forename: T H
authors.initials: TH
authors.lastname: Hasaart
mesh_terms: D000138:Acidosis / Q000209:etiology; D000818:Animals; D003250:Constriction; D004562:Electrocardiography; D005260:Female; D005865:Gestational Age; D006340:Heart Rate, Fetal; D007022:Hypotension / Q000209:etiology; D007700:Kinetics; D011247:Pregnancy; D012756:Sheep / Q000196:embryology; D014470:Umbilical Cord / Q000502:physiology