title: Day-night pattern of autonomic nervous system modulation in patients with heart failure with and without sleep apnea.
abstract: BACKGROUND
  Among patients with congestive heart failure (CHF) both obstructive and central sleep apnea (SA) are associated with increased sympathetic activity. However, the day-night pattern of cardiac autonomic nervous system modulation in CHF patients with and without sleep apnea is unknown.
  
  
  METHODS
  Twenty-five CHF patients underwent polysomnography with simultaneous beat-to-beat blood pressure (Portapres), respiration and electrocardiogram monitoring. Patients were divided according to the presence (SA, n=17) and absence of SA (NoSA, n=8). Power spectral analyses of heart rate variability (HRV) and spontaneous baroreflex sensitivity (BRS) were determined in periods with stable breathing while awake at 6 am, 10 am, 10 pm, as well as during stage 2 sleep. In addition, muscle sympathetic nerve activity (MSNA) was evaluated at 10 am.
  
  
  RESULTS
  RR variance, low-frequency (LF), high-frequency (HF) powers of HRV, and BRS were significantly lower in patients with SA compared with NoSA in all periods. HF power, a marker of vagal activity, increased during sleep in patients with NoSA but in contrast did not change across the 24-hour period in patients with SA. MSNA was significantly higher in patients with SA compared with NoSA. RR variance, LF and HF powers correlated inversely with simultaneous MSNA (r=-0.64, -0.61, and -0.61 respectively; P<0.01).
  
  
  CONCLUSIONS
  Patients with CHF and SA present a reduced and blunted cardiac autonomic modulation across the 24-hour period. These findings may help to explain the increased cardiovascular risk in patients with CHF and SA.
authors.affiliation: School of Arts, Sciences and Humanities, University of São Paulo, São Paulo, Brazil. lindabrz@usp.br
authors.forename: Linda M
authors.initials: LM
authors.lastname: Ueno
authors.forename: Luciano F
authors.initials: LF
authors.lastname: Drager
authors.forename: Ana C T
authors.initials: AC
authors.lastname: Rodrigues
authors.forename: Maria U P B
authors.initials: MU
authors.lastname: Rondon
authors.forename: Wilson
authors.initials: W
authors.lastname: Mathias
authors.forename: Eduardo M
authors.initials: EM
authors.lastname: Krieger
authors.forename: Rubens Fazan
authors.initials: RF
authors.lastname: Júnior
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Negrão
authors.forename: Geraldo
authors.initials: G
authors.lastname: Lorenzi-Filho
mesh_terms: D000328:Adult; D000368:Aged; D001341:Autonomic Nervous System / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography / Q000379:methods; D012891:Sleep Apnea Syndromes / Q000150:complications / Q000503:physiopathology*