title: Autonomic Tone Activity Before the Onset of Atrial Fibrillation.
abstract: BACKGROUND
  The autonomic nervous system has been proven to play a major role in the onset of atrial fibrillation (AF), along with a predisposing substrate and a specific trigger event usually consisting of a premature supraventricular ectopic beat (SVEB). By means of heart rate variability (HRV) analysis, we investigated the activity of the autonomic nervous system before SVEBs nontriggering and triggering AF.
  
  
  RESULTS
  We evaluated 28 patients with at least 1 episode of sustained AF (>30 seconds) recorded during 24-hour Holter monitorings. We performed HRV analysis during the hour preceding 35 AF onsets and compared these results with the HRV values before nontriggering SVEBs with similar prematurity. According to the low frequency (LF)/high frequency (HF) ratio in the 5 minutes before the onset, AF episodes were classified as either vagal (LF/HF ratio <1.5) or adrenergic (LF/HF ratio ≥1.5).Vagal episodes (16) showed a decrease in LF (from 50.81 ± 1.67 to 32.73 ± 3.54) and an increase in HF (from 36.00 ± 2.30 to 54.7 ± 3.69) throughout the hour preceding the onset. Adrenergic episodes (19) had opposite changes in LF (from 55.4 ± 4.95 to 67.51 ± 5.24) and HF (from 33.78 ± 5.82 to 27.96 ± 3.51) during the same period. No similar trends were observed before the selected nontriggering SVEBs.
  
  
  CONCLUSIONS
  Only SVEBs occurring during a phase of hyperactivity of one of the 2 branches of the autonomic nervous system are able to trigger episodes of AF.
authors.affiliation: Division of Cardiology, Department of Medical Sciences, "Città della Salute e della Scienza" Hospital, University of Turin, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Gallo
authors.affiliation: Division of Cardiology, Department of Medical Sciences, "Città della Salute e della Scienza" Hospital, University of Turin, Italy.
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Bocchino
authors.affiliation: Division of Cardiology, Department of Medical Sciences, "Città della Salute e della Scienza" Hospital, University of Turin, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Magnano
authors.affiliation: Division of Cardiology, Department of Medical Sciences, "Città della Salute e della Scienza" Hospital, University of Turin, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Gaido
authors.affiliation: Division of Cardiology, Department of Medical Sciences, "Città della Salute e della Scienza" Hospital, University of Turin, Italy.
authors.forename: Domenica
authors.initials: D
authors.lastname: Zema
authors.affiliation: Division of Cardiology, Department of Medical Sciences, "Città della Salute e della Scienza" Hospital, University of Turin, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Battaglia
authors.affiliation: Division of Cardiology, Department of Medical Sciences, "Città della Salute e della Scienza" Hospital, University of Turin, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Anselmino
authors.affiliation: Division of Cardiology, Department of Medical Sciences, "Città della Salute e della Scienza" Hospital, University of Turin, Italy.
authors.forename: Fiorenzo
authors.initials: F
authors.lastname: Gaita
mesh_terms: D000200:Action Potentials; D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D018880:Atrial Premature Complexes / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D015716:Electrocardiography, Ambulatory; D005260:Female; D006321:Heart / Q000294:innervation*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012307:Risk Factors; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013997:Time Factors; D014630:Vagus Nerve / Q000503:physiopathology*
keywords: atrial fibrillation; autonomic nervous system; ectopic activity; heart rate variability; onset mechanism