title: Paradoxical nocturnal elevation of sympathetic tone and spontaneous ventricular fibrillation in Brugada syndrome.
abstract: BACKGROUND
  Nocturnal dominance of the incidence of spontaneous ventricular tachyarrhythmias has been reported in patients with Brugada syndrome (BrS). The purpose of the present study is to analyze the QT dynamics and autonomic balance as well as their diurnal variations in BrS patients.
  
  
  METHODS
  Of the 33 consecutive patients with BrS included in the study, 14 had a history of cardiopulmonary arrest due to spontaneous ventricular fibrillation (VF) episodes (VF-BrS) and 19 had asymptomatic BrS (A-BrS). QT dynamics and heart rate variability were analyzed using 24-h Holter electrocardiogram recordings.
  
  
  RESULTS
  Of the total 14 first cardiopulmonary arrest episodes due to spontaneous VF, 11 (79%) occurred in VF-BrS patients during the nighttime or at rest. The QT/RR slope during daytime was significantly steeper than that during nighttime in the A-BrS patients (p=0.031), but not in the VF-BrS patients (p=1.0). There were significant diurnal differences pertaining to the high-frequency (HF) and low-frequency (LF)/HF ratios in the A-BrS patients (p=0.019 and p=0.019, respectively), but not in the VF-BrS patients (p=1.0 and p=1.0, respectively). The VF-BrS patients were characterized by relatively high LF/HF ratios, whereas the A-BrS patients were characterized by relatively low LF/HF ratios throughout the daytime and nighttime. Furthermore, the LF/HF ratios during the nighttime in the VF-BrS patients were significantly higher than those in the A-BrS patients (p=0.021).
  
  
  CONCLUSIONS
  Most first episodes of spontaneous VF in the VF-BrS patients occurred during the nighttime or at rest. The autonomic imbalance of paradoxical nocturnal elevation of the sympathetic tone along with an underlying persistent sympathetic tone throughout the day may play a key role for spontaneous VF initiation in BrS patients.
authors.affiliation: Department of Cardiology, Fukuoka University School of Medicine, Fukuoka, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Kumagai
authors.affiliation: Department of Cardiology, Fukuoka University School of Medicine, Fukuoka, Japan; Endowed Department of Advanced Therapeutics for Cardiovascular Disease, Fukuoka University School of Medicine, Fukuoka, Japan. Electronic address: ogawa0376@gmail.com.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ogawa
authors.affiliation: Department of Biochemistry, Fukuoka University School of Medicine, Fukuoka, Japan.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Department of Cardiology, Fukuoka University School of Medicine, Fukuoka, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Koyoshi
authors.affiliation: Department of Cardiology, Fukuoka University School of Medicine, Fukuoka, Japan; Endowed Department of Advanced Therapeutics for Cardiovascular Disease, Fukuoka University School of Medicine, Fukuoka, Japan.
authors.forename: Joji
authors.initials: J
authors.lastname: Morii
authors.affiliation: Department of Cardiology, Fukuoka University School of Medicine, Fukuoka, Japan.
authors.forename: Tomoo
authors.initials: T
authors.lastname: Yasuda
authors.affiliation: Department of Cardiology, Fukuoka University School of Medicine, Fukuoka, Japan.
authors.forename: Naomichi
authors.initials: N
authors.lastname: Matsumoto
authors.affiliation: Department of Cardiology, Fukuoka University School of Medicine, Fukuoka, Japan.
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Matsuo
authors.affiliation: Department of Cardiology, Fukuoka University School of Medicine, Fukuoka, Japan; Endowed Department of Advanced Therapeutics for Cardiovascular Disease, Fukuoka University School of Medicine, Fukuoka, Japan.
authors.forename: Keijiro
authors.initials: K
authors.lastname: Saku
mesh_terms: D000328:Adult; D000368:Aged; D001341:Autonomic Nervous System / Q000503:physiopathology; D053840:Brugada Syndrome / Q000150:complications / Q000503:physiopathology*; D002940:Circadian Rhythm / Q000502:physiology*; D015716:Electrocardiography, Ambulatory; D005260:Female; D006323:Heart Arrest / Q000209:etiology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012146:Rest / Q000502:physiology; D014693:Ventricular Fibrillation / Q000209:etiology*
keywords: Autonomic balance; Brugada syndrome; Cardiopulmonary arrest; QT dynamics; Ventricular fibrillation