title: Role of autonomic tone in the initiation and termination of paroxysmal atrial fibrillation in patients without structural heart disease.
abstract: BACKGROUND
  Previous studies have suggested that paroxysmal atrial fibrillation (PAF) of vagal origin often occurs at night and PAF of sympathetic origin occurs during the daytime; however, autonomic tone after spontaneous termination of PAF has not been determined. The aim of this study was to evaluate by heart rate variability (HRV) analysis the relationship between the time of PAF onset and autonomic tone before and after PAF.
  
  
  RESULTS
  Twenty-three patients (65 +/- 2 years) who underwent 24-hour ambulatory monitoring, had one or more episodes of PAF (>30 min), and had maintained normal sinus rhythm for >60 min before/after PAF were enrolled in this study. Mean duration of PAF was 6.2 +/- 1.2 hours. HRV parameters were analyzed in a 10-minutes section at 60 minutes, 20 minutes, and immediately before the onset of PAF and after its termination. PAF began at night in 14 patients (group N) and during the daytime in 9 patients (group D). In group N, the high-frequency (HF) component and low-frequency (LF) component showed a significant decrease after PAF; PAF was preceded by a gradual increase in HF and LF. Changes in the LF/HF ratio, however, did not occur before or after PAF. Conversely, group D showed a significant increase in the LF/HF ratio before PAF and a decrease in LF and the LF/HF ratio after PAF, but no changes in HF. These changes in HRV parameters were not influenced by the duration or termination time of PAF.
  
  
  CONCLUSIONS
  This study suggests that the autonomic nervous system plays an important role in both the initiation and termination of PAF. Furthermore, the time of PAF onset influences the autonomic tone at the initiation and termination of PAF.
authors.affiliation: First Department of Internal Medicine, Shinshu University, School of Medicine, Matsumoto, Japan. ttomita@hsp.md.shinshu-u.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tomita
authors.forename: Manabu
authors.initials: M
authors.lastname: Takei
authors.forename: Yuko
authors.initials: Y
authors.lastname: Saikawa
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hanaoka
authors.forename: Shin-Ichiroh
authors.initials: S
authors.lastname: Uchikawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tsutsui
authors.forename: Masakazu
authors.initials: M
authors.lastname: Aruga
authors.forename: Toyohisa
authors.initials: T
authors.lastname: Miyashita
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Yazaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Imamura
authors.forename: Osamu
authors.initials: O
authors.lastname: Kinoshita
authors.forename: Mafumi
authors.initials: M
authors.lastname: Owa
authors.forename: Keishi
authors.initials: K
authors.lastname: Kubo
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology*; D001341:Autonomic Nervous System / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology; D004452:Echocardiography; D015716:Electrocardiography, Ambulatory; D005260:Female; D006331:Heart Diseases / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D013564:Sympathetic Nervous System / Q000502:physiology; D013997:Time Factors