Effects of β-blockers on ventilation efficiency in heart failure

BackgroundHyperventilation 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.MethodsWe 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.ResultsThe 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).ConclusionsReduction 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).