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. METHODS AND 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. CONCLUSION: Beta-blockers may be associated with increased ventilatory efficiency in CHF patients, which may contribute to improved functional class and quality of life.