title: Circadian distribution of paroxysmal atrial fibrillation in patients with and without structural heart disease in untreated state.
abstract: BACKGROUND
  This study aimed to compare the circadian distribution of the onset, maintenance and termination of paroxysmal atrial fibrillation (PAF) between structural and non-structural heart diseases (SHD and NSHD, respectively) in the untreated state.
  
  
  METHODS
  We included 217 patients with 338 PAF (79 SHD patients with 131 episodes; 138 NSHD patients with 207 episodes). The probabilities for the onset, maintenance and termination of PAF for each hour were analyzed using Holter monitoring data and harmonic models being fitted into a cosinusoidal function.
  
  
  RESULTS
  The SHD group had a triphasic circadian pattern at the onset with higher peaks at midnight, in the early morning and in the late afternoon (p < 0.05), whereas the NSHD group showed a single peak at midnight (p < 0.01). The probability of maintenance revealed a single peak during midnight (SHD, p < 0.0001; NHD, p < 0.01). The termination showed a peak at noon in the SHD group (p < 0.05), whereas there was a double peak at 10:00 am and 8:00 pm in the NSHD group (p=0.06). RR intervals just after the PAF onset showed marked shortening in the daytime initiation PAF as compared to the nighttime initiation PAF in both SHD and NSHD groups (p < 0.01).
  
  
  CONCLUSIONS
  These observations suggest that the SHD group has very complex onset hours, whereas the NSHD group shows complex termination hours. Reflexly accelerated sympathetic tone just after the PAF onset is suggested in the daytime initiation PAF.
authors.affiliation: Department of Cardiology, Internal Medicine, School of Medicine, Tokai University, Isehara, Japan. deguchi@tc4.so-net.ne.jp
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Deguchi
authors.forename: Mari
authors.initials: M
authors.lastname: Amino
authors.forename: Kumiko
authors.initials: K
authors.lastname: Adachi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Matsuzaki
authors.forename: Osamu
authors.initials: O
authors.lastname: Iwata
authors.forename: Koichiro
authors.initials: K
authors.lastname: Yoshioka
authors.forename: Eiichi
authors.initials: E
authors.lastname: Watanabe
authors.forename: Teruhisa
authors.initials: T
authors.lastname: Tanabe
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology*; D016009:Chi-Square Distribution; D002940:Circadian Rhythm; D015716:Electrocardiography, Ambulatory; D005260:Female; D006331:Heart Diseases / Q000503:physiopathology; D006801:Humans; D016018:Least-Squares Analysis; D008297:Male; D008875:Middle Aged