To compare the responses to oral inotropic and vasodilator drugs, maximally effective doses of amrinone (300 mg over 3 hours) and captopril (25 mg orally) were administered to 21 patients with severe chronic heart failure, who had not received either agent previously. Despite similar decreases in systemic vascular resistance with both drugs, amrinone produced greater increases in cardiac index (+0.56 vs. +0.41/min/m2, p < 0.05) and smaller decreases in mean arterial pressure (-11.1 vs. -15.2 mm Hg, p < 0.05) than did captopril; three patients became symptomatically hypotensive with captopril, but none did so after amrinone. These differences were due to a significant decrease in heart rate with captopril (-6.3 beats/min, p < 0.01), whereas heart rate increased with amrinone (+4.3 beats/min, p < 0.01); the increases in stroke volume index with both drugs were similar. Despite similar decreases in left ventricular filling pressures, the decrease in mean right atrial pressure with amrinone was greater than with captopril (-5.6 vs. -3.2 mm Hg, p < 0.01). This difference was the result of the greater decrease in pulmonary arteriolar resistance, and hence in right ventricular afterload, with amrinone than with captopril, (-33% vs. -16%, respectively), p < 0.01. Despite these superior hemodynamic responses to amrinone, when patients received sequential long-term treatment with both druug during the follow-up period, only 12% of patients benefitted during therapy with amrinone, whereas 64% improved clinically with captopril. In conclusion, although the increases in forward output are greater and the hypotensive risk is less with amrinone than with captopril, these superior short-term hemodynamic effects are not translated into greater long-term clinical benefits.
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