The short-term hemodynamic effects of intravenous enalaprilat were assessed in 
26 infants and children, aged 6 months to 15 years, with intracardiac shunts 
undergoing cardiac catheterization. Pulmonary and systemic pressure, flow, and 
resistance indices were measured by the direct Fick method before and 30 min 
after enalaprilat at 0.06 mg/kg. Aortic and pulmonary artery pressure decreased 
15 and 20%, respectively, by 10 min, with little further change at 30 min. The 
heart rate did not change significantly and there was no reduction in systemic 
flow. In those with a large ventricular septal defect and normal or near-normal 
pulmonary resistance (less than 3.5 u.m2, n = 8), the mean pulmonary-systemic 
flow ratio decreased from 2.9 +/- 0.3 to 2.4 +/- 0.3 (p less than 0.05) and the 
mean left-to-right shunt from 7.4 +/- 0.8 to 5.9 +/- 0.7 L/min/m2 (p less than 
0.02). Those with an elevated pulmonary vascular resistance (greater than 5 
u.m2, n = 8) showed a varied response. Two children, both with Down's syndrome, 
an atrioventricular canal defect, and reversible pulmonary hypertension (as 
assessed by an infusion of isoproterenol), had no decrease in pulmonary vascular 
resistance with enalaprilat. There were no adverse effects. Converting enzyme 
inhibitors may benefit "heart failure" associated with large ventricular septal 
defects and normal or mildly elevated pulmonary resistance.