Angiotensin-converting enzyme inhibition facilitates alveolar-capillary gas transfer and improves ventilation-perfusion coupling in patients with left ventricular dysfunction

Objective: The backward effects of left ventricular dysfunction include alt erations in alveolar-capillary gas transfer and ventilation-perfusion coupl ing. Because the angiotensin-converting enzyme (ACE) is highly concentrated in the vascular endothelium of the lungs, we examined whether ACE inhibito rs may influence the pulmonary function in patients with congestive heart f ailure, Methods: In 20 patients with idiopathic cardiomyopathy, pulmonary function and exercise capacity were evaluated at baseline and 6 and 12 months after treatment with enalapril (10 mg twice a day) was started. The study also in cluded 19 age- and sex-matched control subjects with mild primary hypertens ion and normal left ventricular function who were given enalapril as a stan dard treatment of high blood pressure. Results: In congestive heart failure, forced expiratory volume in 1 second, vital capacity, and total lung capacity did not vary significantly with en alapril; alveolar-capillary diffusion of carbon monoxide (DLCO) increased t oward normal; exercise tolerance time, peak exercise oxygen uptake (peak V- O2), minute ventilation and tidal volume (peak VT) also increased; and the ratio of volume of dead space (VD) to VT (peak VD/VT) at peak exercise redu ced. Changes in peak V-O2 showed a direct correlation with those in DLCO an d an inverse correlation with those in peak VD/VT. Results at 6 and 12 mont hs were comparable. Enalapril did not affect these variables in the control population, Conclusions: In patients with idiopathic cardiomyopathy heart failure, but not in control subjects, gas transfer and ventilation-perfusion improved wi th ACE inhibition. These pulmonary changes may contribute to the associated increase in exercise tolerance.