title: Short-term repeatability of electrocardiographic spatial T-wave axis and QT interval.
abstract: Although ventricular repolarization abnormalities reflect arrhythmic susceptibility, few reliable tools exist to identify their presence. We investigated the repeatability of the spatial T-wave axis and QT interval from standard 12-lead electrocardiograms in 63 asymptomatic volunteers. Certified technicians used a standardized protocol to digitally record 2 electrocardiograms per participant at each of 2 visits separated by 1 to 2 weeks. Absolute paired differences within and between visits were 0.19 degrees and 0.90 degrees for the T-wave axis and 1.08 and 1.55 milliseconds for the QT interval, respectively. The intraclass correlation coefficients for the T-wave axis and QT interval were 0.87 and 0.86, respectively. The impact of repeated measurements on the precision of the QT-interval measurements was evaluated for a hypothetical clinical trial aimed at detecting a drug-induced QT prolongation. We conclude that the spatial T-wave axis is as repeatable a measure of ventricular repolarization as the QT interval.
authors.affiliation: Department of Medicine, University of North Carolina schools of Public Health and Medicine, Chapel Hill, NC 27514, USA. vaidean@email.unc.edu
authors.forename: Georgeta D
authors.initials: GD
authors.lastname: Vaidean
authors.forename: Emily B
authors.initials: EB
authors.lastname: Schroeder
authors.forename: Eric A
authors.initials: EA
authors.lastname: Whitsel
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Prineas
authors.forename: Lloyd E
authors.initials: LE
authors.lastname: Chambless
authors.forename: J Stephen
authors.initials: JS
authors.lastname: Perhac
authors.forename: Gerardo
authors.initials: G
authors.lastname: Heiss
authors.forename: Pentti M
authors.initials: PM
authors.lastname: Rautaharju
mesh_terms: D004562:Electrocardiography / Q000379:methods; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted