title: Age-gender influence on the rate-corrected QT interval and the QT-heart rate relation in families with genotypically characterized long QT syndrome.
abstract: OBJECTIVE
  We sought to analyze age-gender differences in the rate-corrected QT (QTc) interval in the presence of a QT-prolonging gene.
  
  
  BACKGROUND
  Compared with men, women exhibit a longer QTc interval and an increased propensity toward torsade de pointes. In normal subjects, the QTc gender difference reflects QTc interval shortening in men during adolescence.
  
  
  METHODS
  QTc intervals were analyzed according to age (< 16 or > or = 16 years) and gender in 460 genotyped blood relatives from families with long QT syndrome linked to chromosome 11p (KVLQT1; n = 199), 7q (HERG; n = 208) or 3p (SCN5A; n = 53).
  
  
  RESULTS
  The mean QTc interval in genotype-negative blood relatives (n = 240) was shortest in men, but similar among women, boys and girls. For genotype-positive blood relatives, men exhibited the shortest mean QTc interval in chromosome 7q- and 11p-linked blood relatives (n = 194), but not in the smaller 3p-linked group (n = 26). Among pooled 7q- and 11p-linked blood relatives, multiple regression analysis identified both genotype (p < 0.001) and age-gender group (men vs. women/children; p < 0.001) as significant predictors of the QTc interval; and heart rate (p < 0.001), genotype (p < 0.001) and age-gender group (p = 0.01) as significant predictors of the absolute QT interval. A shorter mean QT interval in men was most evident for heart rates < 60 beats/min.
  
  
  CONCLUSIONS
  In familial long QT syndrome linked to either chromosome 7q or 11p, men exhibit shorter mean QTc values than both women and children, for both genotype-positive and -negative blood relatives. Thus, adult gender differences in propensity toward torsade de pointes may reflect the relatively greater presence in men of a factor that blunts QT prolongation responses, especially at slow heart rates.
authors.affiliation: Arrhythmia Center/Sinai Hospital, Detroit, Michigan 48235, USA.
authors.forename: M H
authors.initials: MH
authors.lastname: Lehmann
authors.forename: K W
authors.initials: KW
authors.lastname: Timothy
authors.forename: D
authors.initials: D
authors.lastname: Frankovich
authors.forename: B S
authors.initials: BS
authors.lastname: Fromm
authors.forename: M
authors.initials: M
authors.lastname: Keating
authors.forename: E H
authors.initials: EH
authors.lastname: Locati
authors.forename: R T
authors.initials: RT
authors.lastname: Taggart
authors.forename: J A
authors.initials: JA
authors.lastname: Towbin
authors.forename: A J
authors.initials: AJ
authors.lastname: Moss
authors.forename: P J
authors.initials: PJ
authors.lastname: Schwartz
authors.forename: G M
authors.initials: GM
authors.lastname: Vincent
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002648:Child; D002880:Chromosomes, Human, Pair 11; D002893:Chromosomes, Human, Pair 3; D002897:Chromosomes, Human, Pair 7; D004562:Electrocardiography; D005260:Female; D008040:Genetic Linkage; D005838:Genotype; D006339:Heart Rate / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis / Q000235:genetics* / Q000503:physiopathology; D008297:Male; D012044:Regression Analysis; D012737:Sex Factors; D016171:Torsades de Pointes / Q000235:genetics