title: Circadian change of cardiac autonomic function in correlation with intra-esophageal pH.
abstract: OBJECTIVE
  Although autonomic alterations are observed in patients with gastroesophageal reflux disease (GERD), the influence of visceral receptor responses on the dynamics of autonomic function remains unknown. The aim of this study was to investigate the autonomic functional changes in association with intra-esophageal pH under ambulation.
  
  
  METHODS
  Thirty patients referred for 48 h ambulatory pH monitoring underwent simultaneous 24 h cardiac monitoring for heart rate variability (HRV). We used linear mixed-effects models to estimate the relationship between esophageal acid exposure and power spectral analysis of HRV, including low-frequency power (0.04 < LF < 0.15 Hz), high-frequency power (0.15 < or = HF < 0.4 Hz), and LF/HF power ratio.
  
  
  RESULTS
  Over the 24-h period, patients with pathological reflux had lower average LF and HF powers than patients with functional heartburn, but the LF/HF power ratios were similar for the two patient groups. As we stratified the data according to waking and sleeping times, a significantly higher HF power but lower LF/HF power ratio was found during sleeping time regardless of diagnosis. In the regression analysis, esophageal pH was positively associated with change (not basal tone) of both LF and HF powers during waking, but only with change of HF power during sleeping time. The significant associations between pH values and changes in HRV decreased gradually with time. The LF/HF power ratio did not alter significantly with pH.
  
  
  CONCLUSIONS
  Esophageal acid exposure is generally associated with decreases in autonomic tone. A predominant parasympathetic fluctuation during sleeping and a superimposed sympathetic interaction during waking dictate diurnal characteristics of autonomic regulation.
authors.affiliation: Department of Internal Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Yi-Chia
authors.initials: YC
authors.lastname: Lee
authors.forename: Hsiu-Po
authors.initials: HP
authors.lastname: Wang
authors.forename: Lian-Yu
authors.initials: LY
authors.lastname: Lin
authors.forename: Kai-Jen
authors.initials: KJ
authors.lastname: Chuang
authors.forename: Han-Mo
authors.initials: HM
authors.lastname: Chiu
authors.forename: Ming-Shiang
authors.initials: MS
authors.lastname: Wu
authors.forename: Ming-Fong
authors.initials: MF
authors.lastname: Chen
authors.forename: Jaw-Town
authors.initials: JT
authors.lastname: Lin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001341:Autonomic Nervous System / Q000503:physiopathology*; D002940:Circadian Rhythm / Q000502:physiology*; D015716:Electrocardiography, Ambulatory; D050782:Esophageal pH Monitoring; D005260:Female; D005744:Gastric Acid / Q000378:metabolism / Q000502:physiology; D005764:Gastroesophageal Reflux / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis