title: Corrected QT-interval prolongation and variability in intensive care patients.
abstract: OBJECTIVE
  Critically ill patients are at risk for prolongation of the interval between the Q wave and the T wave in the electrocardiogram (corrected QT [QTc]). Corrected QT prolongation is probably a dynamic process. It is unknown how many patients have a QTc prolongation during their intensive care stay and how variable QTc prolongation is.
  
  
  METHODS
  In a prospective cohort study, continuous 5-minute QTc measurements of 50 consecutive patients were collected. A prolonged QTc interval was more than 500 milliseconds for at least 15 minutes. The QT variance and variability index was used to evaluate QTc variation.
  
  
  RESULTS
  Fifty-two percent of included patients had a prolonged QTc interval. In a single patient, 0.2% to 91.3% of the QTc intervals over time were prolonged. The use of erythromycin and amiodarone was associated with the mean QTc (P = .02 and P = .006, respectively). The Acute Physiology and Chronic Health Evaluation IV and Sequential Organ Failure Assessment scores were significantly higher in patients with a prolonged QTc interval (30.8 vs 8.6 and 7 vs 5.5, respectively). Eighty-four percent of all patients received at least 1 QTc-prolonging drug. The QT variance and QTc variance were significantly higher in patients with a prolonged QTc (P = .019 and P = .001, respectively).
  
  
  CONCLUSIONS
  Continuous QTc monitoring showed a prolonged QTc interval in 52% of intensive care patients. Severity of illness and QT and QTc variances are higher in these patients.
authors.affiliation: Dept of Intensive Care, Onze Lieve Vrouwe Gasthuis, Amsterdam, the Netherlands. Electronic address: evelien.hoogstraaten@live.nl.
authors.forename: Evelien
authors.initials: E
authors.lastname: Hoogstraaten
authors.affiliation: Dept of Intensive Care, Onze Lieve Vrouwe Gasthuis, Amsterdam, the Netherlands. Electronic address: s.rijkenberg@olvg.nl.
authors.forename: Saskia
authors.initials: S
authors.lastname: Rijkenberg
authors.affiliation: Dept of Intensive Care, Onze Lieve Vrouwe Gasthuis, Amsterdam, the Netherlands. Electronic address: p.h.j.vandervoort@olvg.nl.
authors.forename: Peter H J
authors.initials: PH
authors.lastname: van der Voort
mesh_terms: D000328:Adult; D000368:Aged; D003422:Critical Care; D016638:Critical Illness; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D015994:Incidence; D008133:Long QT Syndrome / Q000453:epidemiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies
keywords: Continuous; ECG; Monitoring; Prolongation; QTc; Variability