Effects of β-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. 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.