title: Prevalence and determinants of QT interval prolongation in medical inpatients.
abstract: BACKGROUND
  QT interval prolongation carries an increased risk of torsade de pointes and death.
  
  
  OBJECTIVE
  We sought to determine the prevalence of QT prolongation in medical inpatients and to identify determinants of this condition.
  
  
  METHODS
  We enrolled consecutive patients who were admitted to the internal medicine ward and who had an electrocardiogram performed within 24 h of admission. We collected information on baseline patient characteristics and the use of QT-prolonging drugs. Two blinded readers manually measured the QT intervals. QT intervals were corrected for heart rate using the traditional Bazett formula and the linear regression-based Framingham formula. We used logistic regression to identify patient characteristics and drugs that were independently associated with QTc prolongation.
  
  
  RESULTS
  Of 537 inpatients, 22.3% had a prolonged QTc based on the Bazett formula. The adjusted odds for QTc prolongation based on the Bazett correction were significantly higher in patients who had liver disease (OR 2.9, 95% CI: 1.5-5.6), hypokalaemia (OR 3.3, 95% CI: 1.9-5.6) and who were taking ≥1 QT-prolonging drug at admission (OR 1.7, 95% CI: 1.1-2.6). Overall, 50.8% of patients with QTc prolongation received additional QT-prolonging drugs during hospitalisation.
  
  
  CONCLUSIONS
  The prevalence of QTc prolongation was high among medical inpatients but depended on the method used to correct for heart rate. The use of QT-prolonging drugs, hypokalaemia and liver disease increased the risk of QTc prolongation. Many patients with QTc prolongation received additional QT-prolonging drugs during hospitalisation, further increasing the risk of torsade de pointes and death.
authors.affiliation: Division of General Internal Medicine, University of Lausanne, Lausanne, Switzerland. mathieu.pasquier@chuv.ch
authors.forename: M
authors.initials: M
authors.lastname: Pasquier
authors.forename: O
authors.initials: O
authors.lastname: Pantet
authors.forename: O
authors.initials: O
authors.lastname: Hugli
authors.forename: E
authors.initials: E
authors.lastname: Pruvot
authors.forename: T
authors.initials: T
authors.lastname: Buclin
authors.forename: G
authors.initials: G
authors.lastname: Waeber
authors.forename: D
authors.initials: D
authors.lastname: Aujesky
mesh_terms: D000368:Aged; D004562:Electrocardiography / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006760:Hospitalization; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000453:epidemiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D016171:Torsades de Pointes / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology