title: Heart rate variability in patients with Brugada syndrome in Thailand.
abstract: OBJECTIVE
  Since patients with Brugada syndrome usually have symptoms at nighttime, we hypothesize that changes in autonomic modulation have an important role in the occurrence of the ventricular fibrillation episodes. The objective of this study was to determine the changes in heart rate variability (HRV) in patients with Brugada syndrome compared to asymptomatic subjects with Brugada ECG and controls.
  
  
  RESULTS
  We studied 17 patients with Brugada syndrome, 10 asymptomatic subjects with Brugada ECG and 45 controls. Patients with Brugada syndrome and asymptomatic subjects with Brugada ECG underwent echocardiography, exercise stress testing, 24-h Holter monitoring, signal-averaged ECG. Patients with Brugada syndrome also underwent coronary angiography and electrophysiologic study. Time domain and frequency domain HRV analysis were performed at daytime and nighttime. The results of this study showed that patients with Brugada syndrome had lower HRV or lower vagal tone at night compared to the controls. They also had lower heart rate during the day and higher during the night compared to asymptomatic subjects and the controls.
  
  
  CONCLUSIONS
  Patients with Brugada syndrome had low heart rate variability at night which may predispose to the occurrence of VF episodes.
authors.affiliation: Division of Cardiology, Department of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand. sirkt@mahidol.ac.th
authors.forename: Rungroj
authors.initials: R
authors.lastname: Krittayaphong
authors.forename: Gumpanart
authors.initials: G
authors.lastname: Veerakul
authors.forename: Koonlawee
authors.initials: K
authors.lastname: Nademanee
authors.forename: Charuwan
authors.initials: C
authors.lastname: Kangkagate
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001342:Autonomic Nervous System Diseases / Q000503:physiopathology; D002037:Bundle-Branch Block / Q000503:physiopathology*; D016757:Death, Sudden, Cardiac / Q000209:etiology; D015150:Echocardiography, Doppler; D015716:Electrocardiography, Ambulatory; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D013577:Syndrome; D013785:Thailand; D014693:Ventricular Fibrillation / Q000503:physiopathology*