Background: Angiotensin converting enzyme (ACE) inhibition exerts a favorable effect on the response to exercise in heart failure. This study was planned to define the influence of ACE inhibition on the adaptation to volume overload.
Methods and results: We studied the hemodynamic, hormonal, and renal responses to acute volume expansion (sodium chloride, 0.9%, 0.25 ml.kg-1.min-1 for 2 hours) in patients with idiopathic or ischemic dilated cardiomyopathy and mild heart failure (New York Heart Association class I or II, ejection fraction < or = 50%). The patients were studied without any pretreatment (n = 14) or after 1 week of treatment with the oral ACE inhibitor quinapril at a dosage of 10 mg/day (n = 11). Seven patients were studied during constant intravenous infusion with nitroglycerin (0.1 micrograms.kg-1.min-1). The study groups had similar hemodynamic and clinical characteristics and hormonal profile at baseline evaluation. In the untreated patients, volume expansion did not increase left ventricular end-diastolic volume measured by echocardiography and was associated with a reduction in ejection fraction (p < 0.05) and with a paradoxical increase in forearm vascular resistance (p < 0.05) estimated by plethysmography. In addition, plasma atrial natriuretic factor did not change, and plasma norepinephrine was increased by saline loading. In contrast, in the patients treated with quinapril, volume expansion induced an increase of both left ventricular volumes (p < 0.001) without changing ejection fraction and reduced forearm vascular resistance (p < 0.05). In addition, in this group, plasma atrial natriuretic factor levels increased (p < 0.05) and plasma norepinephrine did not change during volume overload. During nitroglycerin infusion, volume expansion was associated with peripheral vasodilatation, increases of left ventricular volumes, and no change in ejection fraction. In this group, however, plasma atrial natriuretic factor levels did not change in response to volume overload.
Conclusions: We conclude that pretreatment with the ACE inhibitor quinapril significantly improves compromised responses to acute isotonic volume overload in patients with dilated cardiomyopathy and mild heart failure. The favorable influence of ACE inhibition on cardiovascular and hormonal responses to volume expansion seems to be related to the cardiac unloading produced by this treatment.