title: Short-term repeatability of electrocardiographic P wave indices and PR interval.
abstract: BACKGROUND
  P wave indices and PR interval from 12-lead electrocardiograms (ECGs) are predictors of cardiovascular morbidity and mortality, but their repeatability has not been examined.
  
  
  OBJECTIVE
  Determine the short-term repeatability of P wave indices (P axis, maximum P area and duration, P dispersion and P terminal force in V1) and PR interval.
  
  
  METHODS
  Participants (n=63) underwent two standard ECGs at each of two visits, two weeks apart. We calculated the intra-class correlation coefficient (ICC), weighted kappa, and minimal detectable change and difference.
  
  
  RESULTS
  ICCs were 0.93 for PR interval, 0.78 for P axis, 0.77 for maximum P area, and 0.58 for maximum P duration. Within- and between-visit Kappa were 0.30 and 0.11 for P dispersion, and 0.68 and 0.46 for P terminal force.
  
  
  CONCLUSIONS
  Repeatability of PR duration was excellent, that of P wave axis and maximum area was fair, and maximum P wave duration and terminal force was poor. Repeatability of P wave dispersion was fair within visit, yet poor between visits. These results illustrate potential biases when measurement error of some P wave indices is ignored in clinical and epidemiologic studies.
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. Electronic address: mlmeyer@unc.edu.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Snyder
authors.affiliation: Epidemiological Cardiology Research Center (EPICARE), Division of Public Health Sciences Wake Forest School of Medicine, Division of Public Health Sciences, Winston Salem, NC, USA.
authors.forename: Elsayed Z
authors.initials: EZ
authors.lastname: Soliman
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Whitsel
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Kapuaola S
authors.initials: KS
authors.lastname: Gellert
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Heiss
mesh_terms: D002318:Cardiovascular Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted
keywords: P wave indices; PR interval; Reliability; Repeatability