[Effectiveness of long-term ACE-inhibition on pulmonary diffusion and ventilation-perfusion ratio in chronic heart...

Pulmonary dysfunction contributes to exercise intolerance in patients with chronic heart failure, and ACE-inhibition improves the functional capacity of these subjects. In this study, we investigated whether and how ACE-inhibitors affect pulmonary function and ventilatory response during exercise in chronic heart failure. Twenty patients with idiopathic dilated cardiomyopathy and left ventricular ejection fraction < 35% underwent pulmonary function tests and exercise evaluation with analysis of expired gases before and after 1 year of treatment with enalapril (10 mg bid). To explore whether or not the respiratory influence of ACE-inhibitors is peculiar to the syndrome of cardiac failure, we also studied 19 subjects with mild, untreated primary hypertension who followed the same protocol. In this group, enalapril exerted a neutral effect on pulmonary function. In chronic heart failure patients, lung volumes were abnormal and did not improve after enalapril treatment; on the contrary, alveolar diffusing capacity for carbon monoxide increased towards normal values. Exercise tolerance time, peak exercise oxygen consumption, ventilation, and tidal volume also improved and the dead space to tidal volume ratio was reduced at the peak exercise and intermediate exercise phases (20, 60 W). Changes in carbon monoxide diffusion were positively correlated to those occurring during peak exercise oxygen consumption. A negative correlation was found between the variations in oxygen consumption and those in dead space to tidal volume ratio at peak exercise. We conclude that in patients with chronic heart failure, ACE-inhibition restores diffusing lung properties and improves ventilation-perfusion matching during exercise. In this syndrome, sustained reduction in gas exchange resistance is a fundamental therapeutic property of this class of drugs.