title: Automated versus manual measurement of the QT interval and corrected QT interval.
abstract: BACKGROUND
  The International Conference on Harmonization E14 Guideline specifies detailed assessment of QT interval or corrected QT interval prolongation when developing new drugs. We recently devised new software to precisely measure the QT interval.
  
  
  RESULTS
  The QT intervals of all leads for a selected single heart beat were compared between automated measurement with the new software from Fukuda Denshi and manual measurement. With both automated and manual measurement, QT intervals obtained by the tangent method were shorter than those obtained by the differential threshold method, but the extent of correction was smaller. QT interval data obtained by the differential threshold method were more similar to values obtained by visual measurement than were data obtained by the tangent method, but the extent of correction was larger. Variability was related to the T-wave amplitude and to setting the baseline and tangent in the tangent method, while skeletal muscle potential noise affected the differential threshold method. Drift, low-amplitude recordings, and T-wave morphology were problems for both methods. Among the 12 leads, corrections were less frequent for leads II and V(3) -V(6) .
  
  
  CONCLUSIONS
  We conclude that, for a thorough assessment of the QT/QTc interval, the tangent method or the differential threshold method appears to be suitable because of smaller interreader differences and better reproducibility. Correction of data should be done by readers who are experienced in measuring the QT interval. It is also important for electrocardiograms to have little noise and for a suitable heart rate and appropriate leads to be selected.
authors.affiliation: Department of Medicine, Division of Cardiology, Nihon University School of Medicine, Tokyo, Japan. kasamaki@med.nihon-u.ac.jp
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kasamaki
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ozawa
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Ohta
authors.forename: Akira
authors.initials: A
authors.lastname: Sezai
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamaki
authors.forename: Mutsuo
authors.initials: M
authors.lastname: Kaneko
authors.forename: Ichiro
authors.initials: I
authors.lastname: Watanabe
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hirayama
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Nakayama
mesh_terms: D000328:Adult; D004341:Drug Evaluation; D064420:Drug-Related Side Effects and Adverse Reactions; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D017408:Guidelines as Topic; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology*; D006801:Humans; D008133:Long QT Syndrome / Q000139:chemically induced / Q000503:physiopathology; D008297:Male; D012016:Reference Values; D018570:Risk Assessment; D012984:Software; D012986:Software Validation