right ventricular function: predominance of afterload reduction

Although the bipyridine agent amrinone is reported to have a positive inotropic effect on the left ventricle, the effect of this drug on right ventricular contractility in the clinical setting is unknown. We studied the effect of short-term intravenous administration of amrinone on right ventricular systolic function in nine patients with severe congestive heart failure and, using radionuclide ventriculography, examined the right ventricular end-systolic pressure-volume relationship to determine whether reduced right ventricular afterload or increased contractility predominantly accounted for the observed improvement in right ventricular systolic function. In each patient the right ventricular end-systolic pressure-volume relationship was derived with use of varying doses of nitroprusside. After nitroprusside was stopped, intravenous amrinone (3 mg/kg) caused decreases from baseline in pulmonary arterial end-systolic pressure in eight of nine patients (23 ± 11% [overall mean ± SE], p < .05), and in pulmonary vascular resistance in all patients (38 ± 6%, p < .001). Right ventricular endsystolic volume decreased (23 8%, p < .01) and right ventricular ejection fraction increased (31 ± 10%, p = .01). The amrinone-induced decrease in right ventricular end-systolic volume was compared with that predicted for right ventricular afterload reduction alone based on the effect of amrinone on pulmonary arterial end-systolic pressure and the pressure-volume relationship observed during infusion of nitroprusside. With amrinone, a trend was observed toward a shift in the right ventricular endsystolic pressure-volume relationship in seven of nine patients; however, for the group as a whole, the observed effect of amrinone was not significantly different from that predicted from the degree of right ventricular afterload reduction. In conclusion, in patients with severe congestive heart failure, amrinone decreases right ventricular afterload, reduces right ventricular end-systolic volume, and increases right ventricular ejection fraction. The effect of amrinone on right ventricular systolic function results predominantly from right ventricular afterload reduction. Circulation 74, No. 2, 359-366, 1986. THE BIPYRIDINE COMPOUND amrinone has been shown to have both inotropic and vasodilator actions in isolated tissue preparations' and to improve hemodynamics in patients with congestive heart failure.4 '3 Examination of both isovolumetric phase contractile indexes4 and ventricular end-systolic pressure-volume relationships'3 have indicated that at least some of the hemodynamic responses observed in man during the infusion of amrinone may be attributed to augmented left ventricular inotropic state. From the Departments of Medicine and Radiology, Tufts University and New England Medical Center, Boston. Supported in part by grants from the American Heart Association, Dallas, and the American Lung Association, New York. Address for correspondence: Marvin A. Konstam, M.D., Division of Cardiology, Tufts-New England Medical Center, Box 108, 171 Harrison Ave., Boston, MA 02111. Received Nov. 26, 1985; revision accepted May 15, 1986. Vol. 74, No. 2, August 1986 The effect of amrinone on the right ventricle has not been extensively studied and its effect on right ventricular contractility has not been demonstrated. In patients with congestive heart failure, amrinone reduces pulmonary arterial pressure,4'5 presumably due to combined effects on left ventricular contractility and systemic and pulmonary vascular tone. The resulting diminution in right ventricular afterload would be expected to improve right ventricular systolic performance. The extent to which augmented contractility of the thin-walled right ventricle contributes to improved right ventricular ejection during the infusion of amrinone is unknown. Using radionuclide ventriculography in patients with congestive heart failure, we have previously demonstrated a linear relationship between pulmonary arterial end-systolic pressure and right ventricular endsystolic volume during administration of vasodilators 359 by gest on O cber 9, 2017 http://ciajournals.org/ D ow nladed from