title: Validation of continuous QTc measurement in critically ill patients.
abstract: BACKGROUND
  Prolongation of the corrected QT interval (QTc) can lead to torsades de pointes. This study is designed to determine the validity of the continuous QTc (cQTc) measurement in critically ill patients.
  
  
  METHODS
  In a retrospective cohort study, QTc analysis was performed with manual measurements on a single selected lead from a 12-lead ECG and cQTc measurement obtained at the same time. In addition, automated QTc measurement from the 12-lead ECG was also included in the study. Validation was performed by calculating intraclass correlation coefficient (ICC), Pearson's correlation and Bland-Altman plot.
  
  
  RESULTS
  119 patients with QRS<120 ms were included with a mean cQTc of 468 ms (standard deviation (SD) 37) and mean manually measured QTc of 449 ms (SD 41) (p<0.001). Pearson's correlation was 0.65 (p<0.01), ICC was 0.65 (95% CI: 0.53-0.74). Bland-Altman plot shows a mean difference of 19.5 ms (limits of agreement (LOA) -44.6 to 83.7). For cQTc compared to automated QTc from the 12-lead ECG the intraclass correlation coefficient was 0.77 (95% CI: 0.68-0.83, p<0.001) and the Bland-Altman plot shows a mean difference of 7.8 ms (LOA -40.2 to 55.8).
  
  
  CONCLUSIONS
  cQTc measurement in critically ill patients with a QRS duration shorter than 120 ms shows an acceptable accuracy to be used in routine care.
authors.affiliation: Department of Intensive Care, Onze Lieve Vrouwe Gasthuis, P.O. Box 95500, Amsterdam, The Netherlands.
authors.forename: Guido H W
authors.initials: GH
authors.lastname: Janssen
authors.affiliation: Department of Intensive Care, Onze Lieve Vrouwe Gasthuis, P.O. Box 95500, Amsterdam, The Netherlands.
authors.forename: Saskia
authors.initials: S
authors.lastname: Rijkenberg
authors.affiliation: Department of Intensive Care, Onze Lieve Vrouwe Gasthuis, P.O. Box 95500, Amsterdam, The Netherlands; TIAS school for Business and society, Tilburg University, Tilburg, 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: D000368:Aged; D000465:Algorithms; D003422:Critical Care / Q000379:methods*; D016638:Critical Illness / Q000145:classification*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D016171:Torsades de Pointes / Q000175:diagnosis*
keywords: Continuous measurement; Critical care; Intensive care; QTc; Torsades de pointes; Validation