title: QTc interval prolongation in children with Turner syndrome: the results of exercise testing and 24-h ECG.
abstract: BACKGROUND
  Turner syndrome (TS) is the most common sex chromosome abnormality in females. Recently, a prolongation of the rate-corrected QT (QTc) interval in the electrocardiogram (ECG) of TS patients has been reported. A prolonged QTc interval has been correlated to an increased risk for sudden cardiac death, and medical treatment is warranted in patients with congenital long QT syndrome (LQTS). Additionally, several drugs of common use are contraindicated in LQTS because of their effects on myocardial repolarization. The importance of the QTc prolongation in TS patients is not known at present.
  
  
  METHODS
  Eighteen TS patients with a prolonged QTc interval (group 1) and 11 TS patients with a normal QTc interval (group 2) (mean age 12.6+/-3.1 vs. 11.8+/-2.1 years, respectively) were tested. The QTc interval was calculated during exercise testing and during 24-h ECG recordings.
  
  
  RESULTS
  None of the patients experienced adverse cardiac events during the tests. The mean QTc interval decreased from 0.467 to 0.432 s in group 1 and from 0.432 to 0.412 s in group 2. During the 24-h ECG, the maximum QTc interval was significantly prolonged in group 1 (0.51 vs. 0.465 s, p<0.05, respectively). We conclude that exercise testing and 24-h ECG recording provide valuable information about the cardiac risk in the single TS patient with a prolonged QTc interval. This helps in counseling these girls, as clear therapeutic guidelines are currently lacking.
authors.affiliation: Department of Pediatric Cardiology, Ludwig-Maximilians-University, Marchioninistr. 15, 81377, Munich, Germany, Robert.DallaPozza@med.uni-muenchen.de.
authors.forename: Robert
authors.initials: R
authors.lastname: Dalla Pozza
authors.forename: Susanne
authors.initials: S
authors.lastname: Bechtold
authors.forename: Simon
authors.initials: S
authors.lastname: Urschel
authors.forename: Heinrich
authors.initials: H
authors.lastname: Netz
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Schwarz
mesh_terms: D002648:Child; D015897:Comorbidity; D016757:Death, Sudden, Cardiac / Q000453:epidemiology; D003710:Demography; D015716:Electrocardiography, Ambulatory; D015444:Exercise; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D012720:Severity of Illness Index; D014424:Turner Syndrome / Q000453:epidemiology*