title: Abnormal nocturnal heart rate variability and QT dynamics in patients with Brugada syndrome.
abstract: BACKGROUND
  In Brugada syndrome (BSY), most of the ventricular arrhythmic events are nocturnal, suggesting an influence of the autonomic nervous system.
  
  
  METHODS
  In 46 patients (mean age = 41 +/- 14 years, 43 men) with electrocardiograms (ECG) consistent with BSY and structurally normal hearts, we measured heart rate variability (HRV) and QT dynamics (QT/RR slopes) on 24-hour ambulatory ECG. Type 1 BSY-ECG was spontaneous in 23 (50%) and induced in 23 patients.
  
  
  RESULTS
  History of syncope was present in 23 patients (50%). Programmed ventricular stimulation induced ventricular tachyarrhythmias (VTA) in 13 patients (28%). A single patient developed ventricular tachycardia during a mean follow-up of 34 months. Compared to a control group matched for age and sex, HRV was decreased over 24 hours and during nighttime in patients with BSY (SDNN 122 +/- 44 vs 93 +/- 36 ms, P = 0.0008 and SDANN 88 +/- 39 vs 54 +/- 24 ms, P < 0.0001). QTend /RR slopes were decreased over 24 hours in patients with BSY (0.159 +/- 0.05 vs 0.127 +/- 0.05, P = 0.003) and particularly at night (0.123 +/- 0.04 vs 0.089 +/- 0.04, P = 0.0001). QTend /RR slopes were significantly decreased during nighttime in patients with spontaneous versus provoked BSY-ECG patterns. By contrast, HRV and QT/RR slopes were similar in symptomatic and asymptomatic patients, whether VTA were induced or not.
  
  
  CONCLUSIONS
  Patients with a BSY-ECG pattern had lower HRV and QT/RR slopes than control subjects during nighttime. High-risk patients with spontaneous BSY-ECG patterns had the lowest nocturnal QTend/RR slopes. These unique repolarization dynamics might be related to the frequent nocturnal occurrence of VTA in BSY.
authors.affiliation: Services de Cardiologie B et Laboratoire D'electrophysiologie Cardiaque, Centre Hospitalier Universitaire Trousseau, 37044 Tours, France.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Pierre
authors.forename: Dominique
authors.initials: D
authors.lastname: Babuty
authors.forename: Philippe
authors.initials: P
authors.lastname: Poret
authors.forename: Cedric
authors.initials: C
authors.lastname: Giraudeau
authors.forename: Olivier
authors.initials: O
authors.lastname: Marie
authors.forename: Pierre
authors.initials: P
authors.lastname: Cosnay
authors.forename: Laurent
authors.initials: L
authors.lastname: Fauchier
mesh_terms: D000328:Adult; D053840:Brugada Syndrome / Q000503:physiopathology*; D016022:Case-Control Studies; D002940:Circadian Rhythm; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000503:physiopathology*