title: Tachycardia in adults with cystic fibrosis is associated with normal autonomic function.
abstract: BACKGROUND
  Whether autonomic dysfunction contributes to tachycardia in cystic fibrosis (CF) is unknown.
  
  
  METHODS
  Heart rate variability (HRV) was assessed to determine high frequency power and the low/high frequency power ratio (HF, LF/HF) as markers of vagal and sympathovagal balance, respectively, under spontaneous and controlled breathing (15 breaths per minute (bpm)) conditions in 17 CF and 17 healthy control subjects.
  
  
  RESULTS
  Under spontaneously breathing conditions, the CF group was tachycardic (75.4 ± 11.2 vs 60.2 ± 9.0 br/min P < 0.001) and tachypnoeic (22.6 ± 5.8 vs 13.6 ± 4.1 br/min, P= 0.001) compared with controls. No significant difference in HRV was observed between groups during spontaneous or controlled breathing. Coexistent diabetes mellitus and β(2) agonist use were not associated with altered autonomic control. During controlled breathing, the CF group showed a negative correlation between forced expiratory volume in 1 s (FEV(1)) % predicted and HF power (P= 0.013, r=-0.59) and a positive correlation between FEV(1) % predicted and LF/HF ratio (P= 0.002, r= 0.69) suggesting an exaggerated normal vagal response.
  
  
  CONCLUSIONS
  CF patients have normal autonomic function.
authors.affiliation: Department of Allergy Immunology and Respiratory Medicine, Alfred Hospital, Department of Medicine and Nutrition, Monash University, Melbourne, Victoria, Australia.
authors.forename: I
authors.initials: I
authors.lastname: Szollosi
authors.forename: S J
authors.initials: SJ
authors.lastname: King
authors.forename: J W
authors.initials: JW
authors.lastname: Wilson
authors.forename: M T
authors.initials: MT
authors.lastname: Naughton
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D003550:Cystic Fibrosis / Q000150:complications / Q000503:physiopathology*; D048909:Diabetes Complications / Q000150:complications / Q000503:physiopathology; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D015656:Respiratory Mechanics / Q000502:physiology; D013610:Tachycardia / Q000150:complications / Q000503:physiopathology*; D055815:Young Adult