Abstract P015: Short-Term Repeatability of Electrocardiographic P Wave Indices and PR Interval
Background: Despite the growing use of P wave indices and PR interval (PR) from resting, standard 12-lead electrocardiograms (ECGs) as predictors of atrial fibrillation, other forms of cardiovascular disease and all-cause mortality, the repeatability of these ECG measures has not been sufficiently examined.
Objectives: Characterize the repeatability and minimal detectable change of P wave indices and PR.
Methods: Participants (n=63; mean age 52 years; 31 females) underwent two standardized visits one week apart. At each visit, trained and certified technicians obtained two ECGs following a standardized protocol. The Epidemiology Cardiology Research (EPICARE) Center automatically processed the ECGs using GE Marquette GE 12-SL software (GE, Milwaukee, WI), yielding measures of PR duration, P wave maximum area, maximum duration, dispersion and terminal force in lead V1. We used random-effects, mixed models to parse the variance of the measures into their between-participant, between-visit, and within-visit components, then calculated the intra-class correlation coefficient (ICC), weighted Kappa for quartiles of non-normally distributed variables, and minimal detectable change (95% confidence) between repeat measures.
Results: Between-participant variation accounted for 93% to 58% of the total variation in PR duration, P wave maximum area and duration. The ICCs (95% confidence intervals) were 0.93 (0.90, 0.96) PR duration, 0.77 (0.67, 0.86) for P wave maximum area, and 0.58 (0.46, 0.70) for maximum duration. The within-visit weighted Kappa (95% confidence intervals) was 0.26 (0.13, 0.40) and 0.67 (0.57, 0.77) for P wave dispersion and terminal force. The corresponding between-visit weighted Kappa was 0.11 (-0.03, 0.25) and 0.43 (0.31, 0.56) for P wave dispersion and terminal force. Minimal detectable changes between repeat measures of PR duration, P wave maximum area and duration were ≥20 ms, ≥161 μV*ms, and ≥21 ms.
Conclusion: While repeatability of PR duration is excellent, that of P wave maximum area, duration, and terminal force is fair. Repeatability of P wave dispersion is fair within, yet poor between visits. These results support the use of PR duration in clinical and epidemiologic studies, but also illustrate the potential for bias when such studies ignore the error with which other P wave indices are measured.
- © 2013 by American Heart Association, Inc.