Effect of Nitroprusside on Hydraulic Vascular Loads on the Right and Left Ventricle of Patients with Heart Failure

SUMMARY We studied the effect of nitroprusside on the hydraulic vascular load of the right and left ventricle in seven patients with severe left ventricular failure. At doses of 0.25-0.75,ug/kg/min, stroke volume increased progressively from 40.1 to 48.6 ml and left ventricular end-diastolic pressure decreased from 24.5 to 11.2 mm Hg. Accompanying this improvement in left ventricular performance were dose-related decreases in mean ventricular pressures, pulmonic and systemic resistances and the lower-frequen-cy components of input impedance moduli. Characteristic impedance and both total and oscillatory exter-nal power were decreased in the pulmonic, but not the aortic, vasculature. In this class of patients, right ventricular unloading is a striking and direct effect of nitroprusside and may account, in part, for imnproved left ventricular performance through ventricular interdependence. VASODILATORS have become a mainstay in the treatment of acute and chronic left ventricular failure. 1-9 In many patients, they improve forward output while decreasing left ventricular filling pressures. The im-provement in ventricular function has been attributed primarily to lowering of the arterial load or impedanc