Lung function with carvedilol and bisoprolol in chronic heart failure: Is β selectivity relevant?

Background: Carvedilol is a β-blocker with similar affinity for β₁- and β₂ receptors, while bisoprolol has higher β₁ affinity. The respiratory system is characterized by β₂-receptor prevalence. Airway β receptors regulate bronchial tone and alveolar β receptors regulate alveolar fluid re-absorption which influences gas diffusion. Aims: To compare the effects of carvedilol and bisoprolol on lung function in patients with chronic heart failure (CHF). Methods and results: We performed a double-blind, cross-over study in 53 CHF patients. After 2 months of full dose treatment with either carvedilol or bisoprolol, we assessed lung function by salbutamol challenge, carbon monoxide lung diffusion (DLco), including membrane conductance (DM), and gas exchange during exercise. FEV₁ and FVC were similar; after salbutamol FEV₁ was higher with bisoprolol (p <0.04). DLco was 82 ± 21% of predicted with carvedilol and 90 ± 20% with bisoprolol (p <0.01) due to DM changes. Peak VO₂ was 17.8 ± 4.5 mL/min/kg on bisoprolol and 17.0 ± 4.6 on carvedilol, (p <0.05) with no differences in bronchial tone (same expiratory time) throughout exercise. Differences were greater in the 22 subjects with DLco <80%. Conclusion: Carvedilol and bisoprolol have different effects on DLco and response to salbutamol. DLco differences, being DM related, are due to changes in active membrane transport which is under alveolar β₂-receptor control. Peak VO₂ was slightly higher with bisoprolol particularly in CHF patients with reduced DLco.