title: Cardiac autonomic function and oesophageal acid sensitivity in patients with non-cardiac chest pain.
abstract: BACKGROUND
  Acid reflux can elicit non-cardiac chest pain (NCCP), possibly through altered visceral sensory or autonomic function. The interactions between symptoms, autonomic function, and acid exposure are poorly understood.
  
  
  OBJECTIVE
  To examine autonomic function in NCCP patients during exposure to oesophageal acid infusion.
  
  
  METHODS
  Autonomic activity was assessed using power spectral analysis of heart rate variability (PSHRV), before and during oesophageal acidification (0.1 N HCl), in 28 NCCP patients (40.5 (10) years; 13 females) and in 10 matched healthy controls. Measured PSHRV indices included high frequency (HF) (0.15-0.5 Hz) and low frequency (LF) (0.06-0.15 Hz) power to assess vagal and sympathetic activity, respectively.
  
  
  RESULTS
  A total of 19/28 patients had angina-like symptoms elicited by acid. There were no significant manometric changes observed in either acid sensitive or insensitive patients. Acid sensitive patients had a higher baseline heart rate (82.9 (3.1) v 66.7 (3.5) beats/min; p<0.005) and lower baseline vagal activity (HF normalised area: 31.1 (1.9)% v 38.9 (2.3)%; p< 0.03) than acid insensitive patients. During acid infusion, vagal cardiac outflow increased (p<0.03) in acid sensitive but not in acid insensitive patients.
  
  
  CONCLUSIONS
  Patients with angina-like pain during acid infusion have decreased resting vagal activity. The symptoms elicited by perception of acid are further associated with a simultaneous increase in vagal activity in keeping with a vagally mediated pseudoaffective response.
authors.affiliation: Division of Gastroenterology, McMaster University, Hamilton, Ontario, Canada. tougasg@mcmaster.ca
authors.forename: G
authors.initials: G
authors.lastname: Tougas
authors.forename: R
authors.initials: R
authors.lastname: Spaziani
authors.forename: S
authors.initials: S
authors.lastname: Hollerbach
authors.forename: V
authors.initials: V
authors.lastname: Djuric
authors.forename: C
authors.initials: C
authors.lastname: Pang
authors.forename: A R
authors.initials: AR
authors.lastname: Upton
authors.forename: E L
authors.initials: EL
authors.lastname: Fallen
authors.forename: M V
authors.initials: MV
authors.lastname: Kamath
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001341:Autonomic Nervous System / Q000503:physiopathology*; D016022:Case-Control Studies; D002637:Chest Pain / Q000209:etiology / Q000503:physiopathology; D016002:Discriminant Analysis; D004562:Electrocardiography / Q000379:methods; D005260:Female; D005764:Gastroesophageal Reflux / Q000150:complications / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D008297:Male; D008365:Manometry; D008875:Middle Aged; D012815:Signal Processing, Computer-Assisted; D014630:Vagus Nerve / Q000503:physiopathology