title: Neurochemical evidence of cardiac sympathetic activation and increased central nervous system norepinephrine turnover in severe congestive heart failure.
abstract: OBJECTIVE
  The aim of this study was to characterize cardiac sympathetic nervous function in patients with severe heart failure and to investigate the influence of the cause of heart failure, hemodynamic variables and central nervous system catecholamine release on cardiac sympathetic tone.
  
  
  BACKGROUND
  Although heart failure is generally accompanied by sympathoexcitation, the integrity of cardiac sympathetic nerve function in heart failure remains controversial, particularly in relation to nerve firing activity and to the capacity of sympathetic nerves to recapture norepinephrine. Additionally, the location of the afferent and central neural pathways implicated in heart failure-induced sympathoexcitation remains unclear.
  
  
  METHODS
  Radiotracer techniques were applied in 41 patients with severe heart failure and 15 healthy control subjects to study the biochemical aspects of whole body and cardiac sympathetic activity. Hemodynamic indexes of cardiac performance were measured in the heart failure group, and their association with sympathetic activity was studied. Jugular venous catechol spillover was measured to study the central noradrenergic control of sympathetic outflow.
  
  
  RESULTS
  Sympathoexcitation was evident in the heart failure group, reflected by a 62% increase (p < 0.001) in total body and a 277% increase (p < 0.001) in cardiac norepinephrine spillover rates. These changes were accompanied by significant increases in the cardiac spillover of the norepinephrine precursor dihydroxyphenylalanine, the sympathetic cotransmitter neuropeptide Y and the extraneuronal metabolite 3-methoxy-4-hydroxyphenylglycol. The level of cardiac sympathetic activity was significantly correlated (r = 0.59, p < 0.001) with the mean pulmonary artery pressure. An increase in the spillover of dihydroxyphenylalanine and 3-methoxy-4-hydroxyphenylglycol from the brain was present, suggesting activation of central noradrenergic neurons.
  
  
  CONCLUSIONS
  Cardiac sympathetic activation is present in severe heart failure, bearing a close relation with pulmonary artery pressures, independent of heart failure etiology. Activation of noradrenergic neurons in the brain is also present and may be the underlying central nervous mechanism of the sympathoexcitation observed in heart failure.
authors.affiliation: Alfred and Baker Medical Unit, Baker Medical Research Institute, Melbourne, Australia.
authors.forename: D M
authors.initials: DM
authors.lastname: Kaye
authors.forename: G W
authors.initials: GW
authors.lastname: Lambert
authors.forename: J
authors.initials: J
authors.lastname: Lefkovits
authors.forename: M
authors.initials: M
authors.lastname: Morris
authors.forename: G
authors.initials: G
authors.lastname: Jennings
authors.forename: M D
authors.initials: MD
authors.lastname: Esler
mesh_terms: D001921:Brain / Q000378:metabolism*; D004295:Dihydroxyphenylalanine / Q000378:metabolism; D006321:Heart / Q000294:innervation*; D006333:Heart Failure / Q000209:etiology / Q000503:physiopathology*; D006801:Humans; D008734:Methoxyhydroxyphenylglycol / Q000378:metabolism; D008875:Middle Aged; D009478:Neuropeptide Y / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism*; D011669:Pulmonary Wedge Pressure / Q000502:physiology; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013815:Thermodilution
chemical_list: D009478:Neuropeptide Y; D008734:Methoxyhydroxyphenylglycol; D004295:Dihydroxyphenylalanine; D009638:Norepinephrine