Effects of β-blockers on ventilation efficiency in heart failure

Background: Hyperventilation and consequent reduction of ventilation (VE) efficiency are frequently observed during exercise in heart failure (HF) patients, resulting in an increased slope of VE/carbon dioxide (VE/Vco2) relationship. The latter is an independent predictor of HF prognosis. β-Blockers improve the prognosis of HF patients. We evaluated the effect on the efficiency of VE of a β1-β2 unselective (carvedilol) versus a β1 selective (bisoprolol) β-blocker. Methods: We analyzed consecutive maximal cardiopulmonary exercise tests performed on 572 clinically stable HF patients (New York Heart Association class I-III, left ventricle ejection fraction ≤50%) categorized in 3 groups: 81 were not treated with β-blocker, 304 were treated with carvedilol, and 187 were treated with bisoprolol. Clinical conditions were similar. Results: The VE/Vco2 slope was lower in carvedilol- compared with bisoprolol-treated patients (29.7 ± 0.4 vs 31.6 ± 0.5, P = .023, peak oxygen consumption adjusted) and with patients not receiving β-blockers (31.6 ± 0.7, P = .036). Maximum end-tidal CO2 pressure during the isocapnic buffering period was higher in patients treated with carvedilol (39.0 ± 0.3 mm Hg) than with bisoprolol (37.2 ± 0.4 mm Hg, P < .001) and in patients not receiving β-blockers (37.2 ± 0.5 mm Hg, P = .001). Conclusions: Reduction of hyperventilation, with improvement of VE efficiency during exercise (reduction of VE/Vco2 slope and increase of maximum end-tidal CO2 pressure), is specific to carvedilol (β1-β2 unselective blocker) and not to bisoprolol (β1-selective blocker).