title: QT interval in anorexia nervosa.
abstract: OBJECTIVE
  To determine the incidence of a long QT interval as a marker for sudden death in patients with anorexia nervosa and to assess the effect of refeeding. To define a long QT interval by linear regression analysis and estimation of the upper limit of the confidence interval (95% CI) and to compare this with the commonly used Bazett rate correction formula.
  
  
  METHODS
  Prospective case control study.
  
  
  METHODS
  Tertiary referral unit for eating disorders.
  
  
  METHODS
  41 consecutive patients with anorexia nervosa admitted over an 18 month period. 28 age and sex matched normal controls.
  
  
  METHODS
  maximum QT interval measured on 12 lead electrocardiograms.
  
  
  RESULTS
  43.6% of the variability in the QT interval was explained by heart rate alone (p < 0.00001) and group analysis contributed a further 5.9% (p = 0.004). In 6 (15%) patients the QT interval was above the upper limit of the 95% CI for the prediction based on the control equation (NS). Two patients died suddenly; both had a QT interval at or above the upper limit of the 95% CI. In patients who reached their target weights the QT interval was significantly shorter (median 9.8 ms; p = 0.04) relative to the upper limit of the 60% CI of the control regression line, which best discriminated between patients and controls. The median Bazett rate corrected QT interval (QTc) in patients and controls was 435 v 405 ms.s-1/2 (p = 0.0004), and before and after refeeding it was 435 v 432 ms.s1/2 (NS). In 14(34%) patients and three (11%) controls the QTc was > 440 ms.s-1/2 (p = 0.053).
  
  
  CONCLUSIONS
  The QT interval was longer in patients with anorexia nervosa than in age and sex matched controls, and there was a significant tendency to reversion to normal after refeeding. The Bazett rate correction formula overestimated the number of patients with QT prolongation and also did not show an improvement with refeeding.
authors.affiliation: Department of Cardiology, Guy's Hospital, London.
authors.forename: R A
authors.initials: RA
authors.lastname: Cooke
authors.forename: J B
authors.initials: JB
authors.lastname: Chambers
authors.forename: R
authors.initials: R
authors.lastname: Singh
authors.forename: G J
authors.initials: GJ
authors.lastname: Todd
authors.forename: N C
authors.initials: NC
authors.lastname: Smeeton
authors.forename: J
authors.initials: J
authors.lastname: Treasure
authors.forename: T
authors.initials: T
authors.lastname: Treasure
mesh_terms: D000293:Adolescent; D000328:Adult; D000856:Anorexia Nervosa / Q000150:complications* / Q000503:physiopathology / Q000628:therapy; D016022:Case-Control Studies; D016757:Death, Sudden, Cardiac / Q000209:etiology; D004562:Electrocardiography; D005260:Female; D005502:Food; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D015994:Incidence; D008133:Long QT Syndrome / Q000150:complications* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies