Enalapril (MK-421), a new angiotensin-converting enzyme inhibitor. Acute and chronic effects in heart failure.

Enalapril (MK-421) is a new oral angiotensin-converting enzyme inhibitor which was administered to eight patients with chronic congestive heart failure. Four hours after enalapril administration (10 to 20 mg), mean arterial pressure fell from 95.6 +/- 11.4 (SD) to 84.8 +/- 17.6 mm Hg (p less than 0.05), systemic vascular resistance fell from 18.5 +/- 3.0 to 15.8 +/- 4.1 units (p less than 0.02), while pulmonary artery wedge pressure changed insignificantly from 17.5 +/- 9.2 to 14.5 +/- 10.2 mm Hg and cardiac index rose insignificantly from 2.63 +/- 0.46 to 2.82 +/- 0.75 L/min/m2. These hemodynamic effects persisted during one month of enalapril administration. Baseline plasma renin activity of 0.76 +/- 1.07 ng/ml/hr rose to 3.23 +/- 2.87 ng/ml/hr (p less than 0.05) after one month of enalapril administration. During the month of enalapril administration, maximal exercise duration rose from 465.1 +/- 233.0 to 572.3 +/- 233.7 seconds (p less than 0.05), and maximal oxygen uptake increased from 12.3 +/- 2.7 to 16 +/- 11.2 ml/min/kg (p less than 0.05). No major side effect occurred. These sustained effects may be clinically beneficial, and enalapril deserves further evaluation in the long-term treatment of patients with chronic congestive heart failure.