title: Autonomic and cardio-respiratory responses to exercise in Brugada Syndrome patients.
abstract: BACKGROUND
  Imbalances of the autonomic nervous (ANS), the cardiovascular system, and ionics might contribute to the manifestation of The Brugada Syndrome (BrS). Thus, this study has aimed to investigate the cardio-respiratory fitness and the responses of the ANS both at rest and during a sub-maximal exercise stress test, in BrS patients and in gender-matched and age-matched healthy sedentary controls.
  
  
  METHODS
  Eleven BrS patients and 23 healthy controls were recruited in Khon Kaen, Thailand. They performed an exercise test on a cycle ergometer, and during the exercise, expired gas samples and electrocardiograms were collected. Blood glucose and electrolyte concentrations were analyzed before and after exercise. Then the heart rate variability (HRV) and the heart rate recovery (HRR) were analyzed from the electrocardiograms.
  
  
  RESULTS
  The BrS patients showed a higher parasympathetic activation during exercise recovery than baseline. They had a smaller level of sympathetic activation during the period of exercise recovery than the controls did. They also showed a significantly lower peak HR, HRR, and peak oxygen consumption than the controls (p<0.05). All subjects had a significantly lower percentage of peak oxygen consumption and respiratory exchange ratio during low-intensity (p<0.01) and moderate-intensity (p<0.05) exercise than during high-intensity exercise. The BrS patients had mild hyperkalemia which is reduced according to the exercise.
  
  
  CONCLUSIONS
  Thai BrS patients had a more rapid rate of restoration of the parasympathetic and smaller level of sympathetic activation after exercise. They had mild hyperkalemia which is reduced according to the exercise. Furthermore, they exhibited impaired cardio-respiratory fitness.
authors.affiliation: Medical Physiology Program, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand; Exercise and Sport Sciences Research and Development Group, Khon Kaen University, Khon Kaen 40002, Thailand.
authors.forename: Raoyrin
authors.initials: R
authors.lastname: Chanavirut
authors.affiliation: Department of Medicine, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand.
authors.forename: Pattarapong
authors.initials: P
authors.lastname: Makarawate
authors.affiliation: School of Life Sciences, Faculty of Medicine and Health Sciences, The University of Nottingham, Nottingham NG7 2UH, United Kingdom.
authors.forename: Ian A
authors.initials: IA
authors.lastname: Macdonald
authors.affiliation: Exercise and Sport Sciences Research and Development Group, Khon Kaen University, Khon Kaen 40002, Thailand; Department of Physiology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand.
authors.forename: Naruemon
authors.initials: N
authors.lastname: Leelayuwat
keywords: ANS, autonomic nervous system; BrS, total Brugada Syndrome; BrS-D, patients who took anti-arrhythmic drugs; BrS-ND, patients who did not take anti-arrhythmic drugs; Brugada Syndrome; CHO, carbohydrate.; ECG, electrocardiogram; Exercise; HF, high frequency; HR, heart rate; HRR, heart rate recovery; HRV, heart rate variability; Heart rate recovery; Heart rate variability; ICD, implantable cardioverter-defibrillator; K+, potassium; LF, low frequency; O2 peak, peak oxygen consumption; Potassium; RER, respiratory exchange ratio; RMSSD, the square root of the mean of the sum of the squares of differences between adjacent normal to normal intervals; SCD, sudden cardiac death; SDNN, standard deviation of all normal sinus RR intervals; VF, ventricular fibrillation; VT, ventricular tachycardia