title: Atrial fibrillation impairs cardiac sympathetic response to baroreceptor unloading in congestive heart failure.
abstract: OBJECTIVE
  In this study, we investigated for a potential mechanism by which atrial fibrillation (AF) might convey a worse prognosis in congestive heart failure (CHF). Specifically, we aimed to determine whether AF impaired cardiac sympathetic response to baroreceptor unloading in comparison to sinus rhythm (SR) in CHF.
  
  
  RESULTS
  Eighteen CHF patients (ejection fraction 30+/-2%, age 59+/- 2 years), nine in SR and nine in AF, were enrolled. A right heart study and cardiac sympathetic tone assessment by coronary sinus catheter were performed at baseline and after 10 min of 20 degrees and 30 degrees of passive head up tilt (HUT). Filling pressures fell significantly during HUT in both SR and AF groups (AF, P=0.002; SR, P<0.001). The cardiac sympathetic response to HUT was significantly attenuated by AF compared with SR (P=0.014). In conjunction, right atrial appendages were collected from 23 cardiac surgery patients, 12 in SR and 11 in AF to investigate the presence of fibrosis. AF was associated with a significant increase in the collagen density (P=0.025).
  
  
  CONCLUSIONS
  AF is associated with impaired cardiac sympathetic response to baroreceptor unloading compared with SR in CHF, possibly secondary to atrial fibrosis.
authors.affiliation: Wynn Department of Metabolic Cardiology, Baker Heart Research Institute, PO Box 6492, St Kilda Road Central, Melbourne VIC 8008, Australia.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Gould
authors.forename: Michael
authors.initials: M
authors.lastname: Yii
authors.forename: Murray D
authors.initials: MD
authors.lastname: Esler
authors.forename: John M
authors.initials: JM
authors.lastname: Power
authors.forename: David M
authors.initials: DM
authors.lastname: Kaye
mesh_terms: D001281:Atrial Fibrillation / Q000150:complications / Q000503:physiopathology*; D001342:Autonomic Nervous System Diseases / Q000209:etiology / Q000503:physiopathology*; D017704:Baroreflex / Q000502:physiology; D006328:Cardiac Catheterization; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D013318:Stroke Volume / Q000502:physiology; D018487:Ventricular Dysfunction, Left / Q000209:etiology / Q000503:physiopathology