Acute haemodynamic, hormonal and electrolyte effects and short-term clinical response to enalapril in heart failure

To define the short-term haemodynamic, hormonal and electrolyte effects of enalapril in chronic heart failure, we administered it to nine patients. The first dose (5 mg) induced a gradual reduction in plasma angiotensin II, systemic vascular resistance, arterial pressure, heart rate and right heart pressures, the maximum effects occurring within 4-8 h. Angiotensin II levels were still suppressed 24 h after the initial dose, but haemodynamic indices had returned almost to control values by this time. Dose-related increases in cardiac index and plasma renin, and decreases in angiotensin II, systemic vascular resistance and urine aldosterone excretion were seen with 5, 10 and 20 mg enalapril. Cumulative balances for sodium and potassium were positive, plasma potassium increased and plasma antidiuretic hormone fell. After 4-8 weeks of enalapril therapy, clinical status and exercise tolerance improved in the patients who were most severely restricted initially. Enalapril may be useful in the treatment of chronic heart failure.