title: Effects of beta-blocker therapy on ventilatory responses to exercise in patients with heart failure.
abstract: BACKGROUND
  Ventilatory efficiency is the increase in ventilation relative to carbon dioxide production during exercise. Congestive heart failure (CHF) is associated with decreased ventilatory efficiency. beta-blockers improve hemodynamics, prolong survival, and improve functional class in patients with CHF, though peak exercise performance may not improve. We hypothesized beta-blockers increase ventilatory efficiency in patients with CHF.
  
  
  RESULTS
  The study group comprised 614 subjects with left ventricular ejection fraction < or = 40% referred for cardiopulmonary exercise testing. Clinical and exercise data were reviewed and recorded. For comparison, subjects were divided into those treated with beta-blockers (n = 195) and those not treated (n = 419). Subjects on beta-blockers had lower minute ventilation (12 +/- 4 versus 14 +/- 4 L/min, P < .001) at rest, which remained lower during submaximal and maximal exercise, by 4 and 6 L/min, respectively (P = .001). Ventilatory efficiency was increased in subjects treated with beta-blockers at submaximal (32 +/- 6 versus 34 +/- 7, P = .002) and maximal (34 +/- 7 versus 37 +/- 10, P = .005) exercise. Differences between treatment subgroups remained significant by covariate analysis; beta-blockers were also independently associated with decreased minute ventilation by multiple regression.
  
  
  CONCLUSIONS
  Beta-blockers may be associated with increased ventilatory efficiency in CHF patients, which may contribute to improved functional class and quality of life.
authors.affiliation: Division of Cardiovascular Diseases, Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Wolk
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Johnson
authors.forename: Virend K
authors.initials: VK
authors.lastname: Somers
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Allison
authors.forename: Ray W
authors.initials: RW
authors.lastname: Squires
authors.forename: Gerald T
authors.initials: GT
authors.lastname: Gau
authors.forename: Lyle J
authors.initials: LJ
authors.lastname: Olson
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D002227:Carbazoles / Q000627:therapeutic use; D000077261:Carvedilol; D005080:Exercise Test; D017079:Exercise Tolerance / Q000187:drug effects*; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000188:drug therapy* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008790:Metoprolol / Q000627:therapeutic use; D008875:Middle Aged; D011412:Propanolamines / Q000627:therapeutic use; D012123:Pulmonary Ventilation / Q000187:drug effects*; D011788:Quality of Life; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D016896:Treatment Outcome; D016277:Ventricular Function, Left / Q000187:drug effects
chemical_list: D000319:Adrenergic beta-Antagonists; D002227:Carbazoles; D011412:Propanolamines; D000077261:Carvedilol; D008790:Metoprolol