title: Impact of sleep apnea on sympathetic nervous system activity in heart failure.
abstract: OBJECTIVE
  To compare and establish the relevance of the relative degree of sympathetic nervous system activity (SNSA) in groups of patients with congestive heart failure (CHF) and obstructive sleep apnea (OSA), and in a control group.
  
  
  BACKGROUND
  Elevated SNSA is a characteristic feature of CHF, as well as of OSA and nonhypercapnic central sleep apnea (CSA). OSA and CSA commonly occur with CHF; however, the relative contribution of apnea-related hypoxemia and sleep fragmentation to the SNSA of patients with CHF is not known.
  
  
  METHODS
  This was a prospective, controlled, observational trial in which the overnight urinary norepinephrine (UNE) level, which is a measure of integrated overnight SNSA while asleep, was measured in 15 healthy male volunteers, 15 male OSA patients who did not have CHF, and 90 CHF patients (77 men). CHF patients also had right heart pressure measurements and then were grouped by the presence of sleep apnea.
  
  
  RESULTS
  Compared with healthy individuals, the mean (+/- SD) UNE level was significantly elevated in the OSA group and was even further elevated in the CHF group (13.4 +/- 5.6 vs 19.7 +/- 12.3 vs 32.2 +/- 20.2 nmol/mmol creatinine, respectively; p < 0.001 [by analysis of variance]). Within the CHF group, the mean UNE levels were greatest in the CHF-CSA group compared with the CHF-OSA group and the CHF nonapnea group (43.9 +/- 24.1 vs 24.0 +/- 10.8 vs 22.4 +/- 8.9 nmol/mmol creatinine, respectively; p < 0.001). Using a multivariate regression model, the variance of the UNE level in the CHF group was predicted, in descending order, by pulmonary capillary wedge pressure (14% variance), rapid eye movement sleep (8%), and the mean sleep pulse oximetry level (7%).
  
  
  CONCLUSIONS
  Overnight SNSA is significantly greater in CHF patients than in OSA patients. Moreover, the hemodynamic severity of CHF contributes to the elevation of SNSA in CHF patients to a greater degree than apnea-related hypoxemia.
authors.affiliation: Department of Respiratory Medicine, Alfred Hospital, Monash University, Melbourne, Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Solin
authors.forename: David M
authors.initials: DM
authors.lastname: Kaye
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Little
authors.forename: Peter
authors.initials: P
authors.lastname: Bergin
authors.forename: Meroula
authors.initials: M
authors.lastname: Richardson
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Naughton
mesh_terms: D000328:Adult; D003404:Creatinine / Q000652:urine; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006439:Hemodynamics; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009638:Norepinephrine / Q000652:urine; D010092:Oximetry; D017286:Polysomnography; D011446:Prospective Studies; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology*
chemical_list: D003404:Creatinine; D009638:Norepinephrine