title: Inhibition of awake sympathetic nerve activity of heart failure patients with obstructive sleep apnea by nocturnal continuous positive airway pressure.
abstract: OBJECTIVE
  This study was designed to determine whether reductions in morning systolic blood pressure (BP) elicited by treatment of moderate to severe obstructive sleep apnea (OSA) in heart failure (HF) patients are associated with a reduction in sympathetic vasoconstrictor tone.
  
  
  BACKGROUND
  Daytime muscle sympathetic nerve activity (MSNA) is elevated in HF patients with coexisting OSA. In our recent randomized trial in HF, abolition of OSA by continuous positive airway pressure (CPAP) increased left ventricular ejection fraction (LVEF) and lowered morning systolic BP.
  
  
  METHODS
  Muscle sympathetic nerve activity, BP, and heart rate (HR) of medically treated HF patients (EF <45%) and OSA (apnea-hypopnea index > or =20/h of sleep) were recorded on the morning after overnight polysomnography, and again one month after patients were randomly allocated nocturnal CPAP treatment or no CPAP (control).
  
  
  RESULTS
  In nine control patients, there were no significant changes in the severity of OSA, MSNA, systolic BP, or HR. In contrast, in the 8 CPAP-treated patients, OSA was attenuated, and there were significant reductions in daytime MSNA (from 58 +/- 4 bursts/min to 48 +/- 5 bursts/min; 84 +/- 4 bursts/100 heart beats to 72 +/- 5 bursts/100 heart beats; p < 0.001 and p = 0.003, respectively), systolic BP (from 135 +/- 5 mm Hg to 120 +/- 6 mm Hg, p = 0.03), and HR (from 69 +/- 2 min(-1) to 66 +/- 2 min(-1); p = 0.013).
  
  
  CONCLUSIONS
  Treatment of coexisting OSA by CPAP in HF patients lowers daytime MSNA, systolic BP, and HR. Inhibition of increased central sympathetic vasoconstrictor outflow is one mechanism by which nocturnal CPAP reduces awake BP in HF patients with moderate to severe OSA.
authors.affiliation: University Health Network, University of Toronto, 600 University Avenue, Toronto, Ontario M5G 1XS, Canada.
authors.forename: Kengo
authors.initials: K
authors.lastname: Usui
authors.forename: T Douglas
authors.initials: TD
authors.lastname: Bradley
authors.forename: Jonas
authors.initials: J
authors.lastname: Spaak
authors.forename: Clodagh M
authors.initials: CM
authors.lastname: Ryan
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Kubo
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kaneko
authors.forename: John S
authors.initials: JS
authors.lastname: Floras
mesh_terms: D001794:Blood Pressure / Q000502:physiology; D045422:Continuous Positive Airway Pressure; D005260:Female; D006333:Heart Failure / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010543:Peroneal Nerve / Q000503:physiopathology*; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000503:physiopathology* / Q000628:therapy; D013318:Stroke Volume / Q000502:physiology; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014851:Wakefulness / Q000502:physiology*