title: Within- and between-patient variation of the signal-averaged P wave in coronary artery disease.
abstract: OBJECTIVE
  To estimate interobserver, within-patient and between-patient variation of the signal-averaged P wave. To determine whether demographic, clinical, conventional ECG information, and coronary angiographic data are associated with the signal-averaged P wave duration in patients with documented coronary artery disease.
  
  
  BACKGROUND
  A prolonged signal-averaged P wave may indicate the presence of a substrate for atrial tachyarrhythmias and may predict subsequent development of atrial fibrillation. However, information on variation, reproducibility, and determinants of the signal-averaged P wave are sparse.
  
  
  METHODS
  One hundred ninety-three patients with angiographically documented coronary artery disease underwent two consecutive procedures of signal-averaging of P waves (SAECG1 and SAECG2). Interobserver, within-patient, and between-patient variation of the signal-averaged P wave was estimated (coefficient of variation: SD/mean). Multiple linear regression analysis was applied to identify parameters independently associated with signal-averaged P wave duration (SA-P). Atrial late potentials were considered if SA-P > 140 ms, and logistic regression analysis was applied to identify parameters associated with the presence of atrial late potentials.
  
  
  RESULTS
  The interobserver, within-patient, and between-patient coefficients of variation for the signal-averaged P wave duration were 7.5%, 6.0% and 8.4%, respectively. The signal-averaged P wave duration correlated significantly with standard ECG P wave duration and height of the patient (r = 0.59). Forty-nine percent of the patients had atrial late potentials. P wave duration in the standard ECG correctly classified 73% (140/188) of the patients with respect to atrial late potential positivity or negativity. The sensitivity was 67% and the specificity was 78%. Agreement on the presence or absence of atrial late potentials between two observers was present in 71% (136/193) of the patients, and in 78% (151/193) between SAECG1 and SAECG2.
  
  
  CONCLUSIONS
  The signal-averaged P wave has limited reproducibility in patients with coronary artery disease, and a normal or abnormal signal-averaged P wave can be predicted from the conventional ECG with high accuracy. It is recommended that the signal-averaged P wave be compared with the standard ECG P wave duration in follow-up studies with the aim of predicting atrial fibrillation.
authors.affiliation: Department of Cardiology, Skejby Sygehus, University Hospital, Aarhus, Denmark.
authors.forename: E H
authors.initials: EH
authors.lastname: Christiansen
authors.forename: L
authors.initials: L
authors.lastname: Frost
authors.forename: H
authors.initials: H
authors.lastname: Pilegaard
authors.forename: T
authors.initials: T
authors.lastname: Toftegaard-Nielsen
authors.forename: A K
authors.initials: AK
authors.lastname: Pedersen
mesh_terms: D000200:Action Potentials / Q000502:physiology; D001281:Atrial Fibrillation / Q000453:epidemiology; D016275:Atrial Function / Q000502:physiology; D017023:Coronary Angiography; D003327:Coronary Disease / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D004562:Electrocardiography / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012044:Regression Analysis; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted