Decrease by ACE-inhibition of the excessive alveolar-capillary membrane resistance to gas transfer in chronic heart...

Area of Science:

• Cardiology and Pulmonary Medicine
• Pharmacology

Background:

• Chronic heart failure impairs pulmonary diffusion for carbon monoxide (DLco), a measure of lung function.
• Reduced DLco in heart failure is linked to alveolar-capillary membrane dysfunction.

Purpose of the Study:

• To investigate how ACE-inhibitors improve DLco in chronic heart failure.
• To determine the effects of enalapril on DLco subcomponents: alveolar-capillary membrane conductance (DM) and capillary blood volume (VC).

Main Methods:

• Evaluated pulmonary function, DM, and VC in 27 chronic heart failure patients (NYHA class II-III) and 13 controls.
• Measurements were taken at baseline (placebo), 48 hours, and 8 weeks after initiating enalapril (10 mg bid).
• Utilized the Roughton and Forster method for determining DM and VC.

Main Results:

• Enalapril showed no short- or mid-term effects in controls.
• In heart failure patients, enalapril caused a reduction in VC at 48 hours, likely due to decreased pulmonary capillary pressure.
• After 8 weeks, a significant increase in DM/VA was observed, improving DLco despite decreased VC, indicating enhanced membrane diffusion.

Conclusions:

• ACE-inhibition gradually improves alveolar-capillary membrane function in chronic heart failure, independent of pulmonary capillary pressure changes.
• This restoration of membrane diffusive properties enhances gas transfer and offers lung protection in heart failure.
• The findings suggest ACE-inhibitors can reverse derangements in the alveolar-capillary membrane caused by chronic heart failure.