The effects of beta-blockers on exercise parameters in heart failure

Purpose. To examine the outcome of a 6-month treatment with carvedilol or metoprolol on peak and submaximal exercise performance and ventilatory efficiency in patients with heart failure (HF).; Methods. 27 patients with HF were randomized to receive either metoprolol or carvedilol for 6 months and compared with 12 healthy controls. Maximal exercise capacity was assessed at baseline and after 6 months with a symptom limited incremental treadmill protocol (RAMP). Submaximal exercise was determined to be the portion of exercise below a respiratory exchange ratio of 1.0. Peak heart rate (HR), oxygen uptake (VO2), and ventilatory equivalent for O2 and CO2 were recorded. The slopes of the VE vs. VCO2, VE vs. VO2 and VE/VCO2 vs. VO2 relationships were calculated for each subject from submaximal values.; Results. Resting HR decreased to similar extent in both treatment groups. There were no other significant changes in resting hemodynamics or ventricular function. Peak VO2 and HR decreased significantly in both treatment groups. Peak VE/VCO2 and submaximal VCO 2 vs. VE slope were not changed significantly after therapy.; Conclusion. beta-blocker treatment with either metoprolol or carvedilol does not decrease the slope of the VCO2 vs. VE relationship. The present observations may suggest that the exaggerated ventilatory response of patients with moderate HF is not mediated by beta-adrenergic receptors.