title: Short-term repeatability of electrocardiographic Tpeak-Tend and QT intervals.
abstract: BACKGROUND
  The electrocardiographic (ECG) Tpeak-Tend interval (TpTe) is associated with arrhythmias and sudden cardiac death. TpTe offers a supplementary measure for the QT interval (QT), yet its repeatability has not been established.
  
  
  OBJECTIVE
  Evaluate short-term repeatability of TpTe and QT.
  
  
  METHODS
  Four ECGs were obtained on sixty participants. The sources of variation, intra-class correlation coefficient (ICC) - an index of reproducibility - and minimal detectable change (MDC) were estimated for TpTe and QT. The impact of repeated measurements on repeatability was estimated for a hypothetical clinical trial designed to detect drug-induced prolongation of TpTe and QT.
  
  
  RESULTS
  We used heart rate-adjusted QT [(QT)a] but TpTe in the study group was rate-invariant. The ICC [95% confidence interval (CI)] was 0.77 (0.69, 0.85) for TpTe, 0.75 (0.65, 0.85) for QT and 0.60 (0.47, 0.73) for (QT)a. The MDC (ms) was 21, 32 and 26 for TpTe, QT and (QT)a respectively.
  
  
  CONCLUSIONS
  TpTe has excellent repeatability supporting its use as a supplement to QT in observational and clinical studies.
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC. Electronic address: kapuaola@email.unc.edu.
authors.forename: Kapuaola S
authors.initials: KS
authors.lastname: Gellert
authors.affiliation: Department of Public Health Sciences, Epidemiological Cardiology Research Center (EPICARE), Wake Forest University School of Medicine, Winston Salem, NC.
authors.forename: Pentti
authors.initials: P
authors.lastname: Rautaharju
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Snyder
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC; Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Whitsel
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD.
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Matsushita
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Heiss
authors.affiliation: Department of Public Health Sciences, Epidemiological Cardiology Research Center (EPICARE), Wake Forest University School of Medicine, Winston Salem, NC; Department of Medicine, Section on Cardiology, Wake Forest School of Medicine, Winston Salem, NC.
authors.forename: Elsayed Z
authors.initials: EZ
authors.lastname: Soliman
mesh_terms: D000465:Algorithms; D003627:Data Interpretation, Statistical; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Electrocardiogram; QT; Repeat variation T; TpTe interval