Comparison of the Effects of Carvedilol and Metoprolol on Exercise Ventilatory Efficiency in Patients With Congestive Heart Failure

摘要

Background The slope of the relationship between ventilation and carbon dioxide production (VE/VCO_2 slope), obtained during symptom-limited ramp exercise testing, reflects exercise ventilatory efficiency. Importantly, the VE/VCO_2 slope is related to prognosis in patients with congestive heart failure (CHF). The aim of the present study was to determine the relationship between the institution of beta-blockers, carvedilol or metoprolol, and the VE/VCO_2 slope during exercise in patients with CHF. Methods and Results Fifty-seven patients with New York Heart Association functional class II or HI with a radionuclide left ventricular ejection fraction (LVEF) of less than 40% received carvedilol or metoprolol in a randomized fashion. The VE/VCO_2 slope, LVEF and plasma brain natriuretic peptide (BNP) concentration were determined before and after 16 weeks of treatment. LVEF improved (p<0.01), but the VE/VCO_2 slope and BNP did not. A significant improvement in the VE/VCO_2 slope was observed in patients with LVEF <29% or BNP >63pg/ml (respective baseline median values) (p<0.05, p<0.05). In patients with BNP >63pg/ml, the improvement effect on the VE/VCO_2 slope with carvedilol was significantly greater than that with metoprolol (p<0.05) and a significant improvement in the VE/VCO_2 slope was observed only in those who took carvedilol (p<0.01). Conclusions The VE/VCO_2 slope was not improved after beta-blocker therapy in any of the patients. However, it did improve in patients with a lower LVEF or higher BNP level at baseline, and carvedilol was more effective than metoprolol in improving the VE/VCO_2 slope in patients with higher BNP levels at baseline.