title: Beat-to-beat QT interval variability in children: normal and physiologic data.
abstract: BACKGROUND
  QT interval variability provides information on ventricular vulnerability. However, QT interval variability in children has not been adequately evaluated.
  
  
  METHODS
  One hundred seventy-three consecutive nursing infants and children (male-female, 106:67) up to school age with no intrinsic cardiac disease were included in this study, and they were categorized into 6 age-related groups. The QT variability index (QTVI) was calculated based on an electrocardiogram; and age-specific standard values, sex-specific classification, and a standard growth curve covering 0 to 7 years were constructed.
  
  
  RESULTS
  The QTVI decreased in an age-dependent manner, reached constant values after school age, and exhibited no sex-specific differences in 6 age-related groups.
  
  
  CONCLUSIONS
  Based on the age-dependent standardized QTVI values, it is possible to estimate the instability of ventricular repolarization in pediatric patients with better accuracy.
authors.affiliation: Clinical Laboratory, Mie University Hospital, Japan. hiro.kusuki@gmail.com
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Kusuki
authors.forename: Marina
authors.initials: M
authors.lastname: Kuriki
authors.forename: Kayo
authors.initials: K
authors.lastname: Horio
authors.forename: Misa
authors.initials: M
authors.lastname: Hosoi
authors.forename: Hideaki
authors.initials: H
authors.lastname: Matsuura
authors.forename: Masayuki
authors.initials: M
authors.lastname: Fujino
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Eryu
authors.forename: Masafumi
authors.initials: M
authors.lastname: Miyata
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Yasuda
authors.forename: Toshio
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Shunji
authors.initials: S
authors.lastname: Nagaoka
authors.forename: Tadayoshi
authors.initials: T
authors.lastname: Hata
mesh_terms: D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006329:Heart Conduction System / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007223:Infant; D008297:Male; D012016:Reference Values; D018709:Statistics, Nonparametric