title: Relationship between QT and JT peak interval variability in prepubertal children.
abstract: BACKGROUND
  The QT variability index (QTVI) is a noninvasive index of repolarization lability that has been applied to subjects with cardiovascular disease. QTVI provides a ratio of normalized QT variability to normalized heart rate variability, and therefore includes an assessment of autonomic nervous activity. However, measurement of QT time is particularly difficult in children, who exhibit physiologically high heart rates compared with adults. In this study, we developed a set of standard values of J-point to Tpeak interval (JTp) for infants by age, and assessed the correlation of QTVI with the JTp variability index (JTpVI).
  
  
  METHODS
  Subjects included 623 infants and children (0-7 years of age) without heart disease and 57 healthy university students. All subjects were divided into three groups by age. QTVI and JTpVI were calculated based on an electrocardiogram, and age-specific standard values, a gender-specific classification, and a standard growth curve were constructed.
  
  
  RESULTS
  JTpVI markedly decreased in infancy and slowly decreased thereafter, reaching adult values by school age. There was also a strong correlation of JTpVI with QTVI (r = .856).
  
  
  CONCLUSIONS
  JTp can be used to evaluate the variability of the repolarization time in healthy infants, and may be useful for detection of early repolarization abnormalities.
authors.affiliation: Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Takeuchi
authors.affiliation: Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Omeki
authors.affiliation: Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan.
authors.forename: Kayo
authors.initials: K
authors.lastname: Horio
authors.affiliation: Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Nishio
authors.affiliation: Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan.
authors.forename: Rina
authors.initials: R
authors.lastname: Nagata
authors.affiliation: Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Oikawa
authors.affiliation: Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Mizutani
authors.affiliation: Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan.
authors.forename: Arisa
authors.initials: A
authors.lastname: Nagatani
authors.affiliation: Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Funamoto
authors.affiliation: Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Uchida
authors.affiliation: Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Fujino
authors.affiliation: Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Eryu
authors.affiliation: Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Boda
authors.affiliation: Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Miyata
authors.affiliation: Graduate School of Health Sciences, Fujita Health University, Toyoake, Japan.|Department of Pediatrics, School of Medicine, Fujita Health University, Toyoake, Japan.
authors.forename: Tadayoshi
authors.initials: T
authors.lastname: Hata
mesh_terms: D000328:Adult; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D004562:Electrocardiography / Q000379:methods* / Q000706:statistics & numerical data*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007223:Infant; D008297:Male; D015203:Reproducibility of Results; D055815:Young Adult
keywords: JT peak interval; QT interval; autonomic nervous system; variability index