title: Circadian behavior of P-wave duration, P-wave area, and PR interval in healthy subjects.
abstract: BACKGROUND
  The prolongation of P-wave duration has long been shown to indicate the presence of high risk for atrial fibrillation. The circadian variation of P-wave characteristics and their dynamic adaptation to heart rate changes was not tested before.
  
  
  METHODS
  To evaluate the diurnal pattern of P-wave duration, P area, and PR interval and of their linearly fitted relation with RR interval, 50 healthy volunteers (25 men, mean age 34 +/- 10 years) underwent 24-hour ambulatory electrocardiographic (ECG) recording with digital 12-lead Holter recorders. The median P-wave duration, P area, and PR interval were calculated from the average 12-lead ECG constructed from each 10-second ECG recording. Single harmonic regression analysis was performed to reveal the presence of circadian variation in the aforementioned ECG parameters.
  
  
  RESULTS
  The P area (P < 0.0001, R(2) = 0.78), the PR interval (P < 0.0001, R(2) = 0.92), the P area / RR slope (P < 0.0001, R(2) = 0.55), and the PR/RR slope (P < 0.0001, R(2) = 0.42) showed a highly significant circadian variation while the periodic nature of P-wave duration (P = 0.016, R(2) = 0.32) and of the P duration / RR slope (P = 0.011, R(2) = 0.18) was only indicated by harmonic regression analysis.
  
  
  CONCLUSIONS
  P-wave duration, P area, and PR interval show a significant circadian variation in healthy subjects. The relations between P area/RR,PR/ RR, and P duration/RR also demonstrate a significant diurnal pattern.
authors.affiliation: Department of Cardiological Sciences, St George's Hospital Medical School, London, England. hrodil@yahoo.com
authors.forename: P E
authors.initials: PE
authors.lastname: Dilaveris
authors.forename: P
authors.initials: P
authors.lastname: Färbom
authors.forename: V
authors.initials: V
authors.lastname: Batchvarov
authors.forename: A
authors.initials: A
authors.lastname: Ghuran
authors.forename: M
authors.initials: M
authors.lastname: Malik
mesh_terms: D000328:Adult; D001281:Atrial Fibrillation / Q000209:etiology; D002940:Circadian Rhythm / Q000502:physiology*; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012044:Regression Analysis; D012307:Risk Factors; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors