title: Competing autonomic mechanisms precede the onset of postoperative atrial fibrillation.
abstract: OBJECTIVE
  This study was designed to evaluate autonomic changes preceding atrial fibrillation/flutter (AF) after thoracotomy.
  
  
  BACKGROUND
  Autonomic fluctuations before the onset of postoperative AF have been reported but with conflicting results.
  
  
  METHODS
  In 48 patients with postoperative AF, 2-h Holter recordings before the onset of AF were compared with corresponding data from 48 age- and gender-matched surgical controls without AF. Five-minute segments of heart rate variability (HRV) were studied using linear regression methods.
  
  
  RESULTS
  There was a near-significant trend for the RR interval among patients with AF to be lower than controls (p = 0.06), whereas the standard deviation of RRs (p < 0.0001), root mean square of successive RR differences (p < 0.0001), proportion of RRs >50 ms different (p < 0.0001), low-frequency power (p = 0.0003) and its log (p < 0.0001), and high-frequency-power (p < 0.0001) and its log (p < 0.0001) were all significantly greater in patients with AF, respectively. In comparison to controls, AF patients had a significant decrease in RR interval (p = 0.02) and significant increments in all time- and frequency-domain analyses studied.
  
  
  CONCLUSIONS
  In the period before the onset of postoperative AF, there are significant increases in HRV during a time when heart rate also increases. These novel findings are consistent with parasympathetic resurgence competing with increasing sympathetic activity as the triggering mechanism for postoperative AF.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York, USA. amard@mskcc.org
authors.forename: David
authors.initials: D
authors.lastname: Amar
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Saul
authors.initials: S
authors.lastname: Miodownik
authors.forename: Alan H
authors.initials: AH
authors.lastname: Kadish
mesh_terms: D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology*; D001341:Autonomic Nervous System / Q000503:physiopathology*; D016022:Case-Control Studies; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D011183:Postoperative Complications / Q000503:physiopathology*; D011446:Prospective Studies; D019616:Thoracic Surgical Procedures