Effects of beta-blocker therapy on ventilatory responses to exercise in patients with heart failure.
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.
Wolk
Robert
R
Division of Cardiovascular Diseases, Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA.
Johnson
Bruce D
BD
Somers
Virend K
VK
Allison
Thomas G
TG
Squires
Ray W
RW
Gau
Gerald T
GT
Olson
Lyle J
LJ
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
D000319:Adrenergic beta-Antagonists; D002227:Carbazoles; D011412:Propanolamines; D000077261:Carvedilol; D008790:Metoprolol