Hemodynamic and radionuclide effects of acute captopril therapy for heart failure: Changes in left and right ventricular volumes and function at rest and during exercise

Abstract

Although the resting hemodynamic effects of captopril in congestive heart failure are known, little information is available about the hemodynamic response to captopril during exercise or about changes in noninvasive measurements of the size and function of both ventricles. In this study, 14 stable New York Heart Association class III patients were given 25 mg of oral captopril. Rest and exercise hemodynamic measurements and blood poorl scintigrams were performed simultaneously before and 90 minutes after captopril. The radionuclide studies were analyzed for left and right ventricular end-diastolic volumes, end-systolic volumes, ejection fractions and pulmonary blood volume. The primary beneficial responses at rest were decreases in left and right ventricular end-diastolic volumes from 388 ± 81 to 350 ± 77 ml (p < 0.01) and from 52 ± 26 to 43 ± 20 volume units (p < 0.01), respectively, and in their corresponding filling pressures, from 24 ± 10 to 17 ± 9 mm Hg and 10 ± 5 to 6 ± 5 mm Hg (both p < 0.001). Although stroke volume did not increase significantly, both left and right ventricular ejection fractions increased slightly, from 19 ± 6% to 22 ± 5% and from 25 ± 9% to 29 ± 11%, respectively (both p < 0.01). During exercise, similar changes were noted in both hemodynamic and radionuclide indexes. Thus, in patients with moderate symptomatic limitation from chronic heart failure, captopril predominantly reduces ventricular volume and filling pressure, with a less significant effect on cardiac output. These effects persist during exercise, when systemic vascular resistance is already very low. Radionuclide techniques are valuable in assessing the drug effect in these subjects, particularly when ventricular volumes are also measured.