Acute hemodynamic action of captopril in congestive heart failure: contrasts between refractory and untreated patients.

To compare the hemodynamic mode of action of captopril in patients with Congestive Heart Failure (CHF) with high- or low-plasma renin activity, we studied the systemic and renal hemodynamic changes induced by this drug in patients with refractory CHF (Group I) or untreated CHF (Group II). Plasma Renin Activity (PRA) was 7.46 +/- 3.7 ng/ml/hr in Group I and 1.15 +/- 0.45 ng/ml/hr in Group II. After the administration of captopril, these values increased to 14.35 +/- 6.19 and to 1.99 +/- 0.76 ng/ml/hr respectively (p less than 0.05). We observed that patients of Group I responded with increases in cardiac index and stroke volume and diminutions in total peripheral resistance, but Group II did not show any significant change in these variables. In contrast to this difference in responses between the refractory and untreated patients, both groups showed similar decreases in pulmonary artery and wedge pressures. Both groups also showed similar increases in plasma volume and effective renal plasma flow, and decreases in renal vascular resistance. These results show that captopril has predominantly venodilator effects in patients with CHF with low PRA levels, and it acts as a mixed vasodilator in patients refractory to conventional therapy, receiving high doses of diuretics, and in whom PRA is elevated. Our results also suggest that the venodilator action of captopril is not mediated by the Renin-Angiotensin System.