A randomized cross-over study of enalapril in congestive heart failure: haemodynamic and hormonal effects during rest and exercise.

We performed a randomized double-blind placebo controlled cross-over study of enalapril in 16 patients with chronic congestive heart failure, to assess haemodynamic and hormonal effects at rest and on exercise. Acute effects were measured 4 h after enalapril 10 mg, and chronic effects after 6 weeks treatment with enalapril 10-20 mg per day. Exercise tolerance, assessed by the duration of a maximal bicycle ergometer test, was not altered by enalapril. Mean blood pressure was reduced after enalapril, at rest and on exercise, acutely by 7% and 8% respectively, and chronically by 14% and 16%. Systemic vascular resistance was reduced by 16% at rest both acutely (NS) and chronically (p less than 0.05). The resting pulmonary capillary wedge pressure was reduced by 28% with chronic treatment. In the acute study, total body oxygen consumption on exercise was 26% higher after enalapril. Chronically, resting oxygen consumption was reduced by 13% after enalapril, with mixed venous oxygen saturation increasing by 16%. In the acute study enalapril increased plasma renin activity at rest and on exercise by 181% and by 189%, and reduced aldosterone by 49% (NS) and 39% (p less than 0.05), and these effects were sustained after 6 weeks. Enalapril increased antidiuretic hormone concentrations at rest acutely by 73% (NS) and chronically by 34% (p less than 0.05) but not on exercise; the increase in the acute study correlated with plasma enalaprilat levels (r = 0.66, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)