Effects of β-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. β-blockers improve hemodynamics, prolong survival, and improve functional class in patients with CHF, though peak exercise performance may not improve. We hypothesized β-blockers increase ventilatory efficiency in patients with CHF. Methods and Results: The study group comprised 614 subjects with left ventricular ejection fraction ≤40% referred for cardiopulmonary exercise testing. Clinical and exercise data were reviewed and recorded. For comparison, subjects were divided into those treated with β-blockers (n = 195) and those not treated (n = 419). Subjects on β-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 β-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; β-blockers were also independently associated with decreased minute ventilation by multiple regression. Conclusion: β-Blockers may be associated with increased ventilatory efficiency in CHF patients, which may contribute to improved functional class and quality of life.