We report the results of a multicenter study performed on 70 patients with severe congestive heart failure of different etiology (ischemic, idiopathic, alcoholic, valvular and secondary to antiblastic drugs) to evaluate the clinical and hemodynamic effects and tolerability of low dose amrinone iv (0.75 mg bolus followed by a continuous 48-hour infusion at the dose of 5-10 mcg/kg/min). Forty-one patients underwent invasive hemodynamic monitoring with right heart Swan-Ganz catheterization. Heart rate (HR), systolic (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP), cardiac index (CI), stroke volume index (SVI), stroke work index (SWI), right atrial pressure (RAP), pulmonary wedge pressure (PWP), mean arterial pulmonary pressure (PAP), systemic vascular resistance (SVR), pulmonary vascular resistance (PVR) and total pulmonary resistance (TPR) were evaluated before and after 1, 4, 6, 24 and 48 hours of amrinone infusion and 2 and 4 hours after amrinone withdrawal. Clinical parameters (dyspnea, orthopnea, pulmonary congestion) were quantitated using a score; diuresis was assessed hourly; hematochemical parameters were evaluated before and 48 hours after amrinone infusion. HR and MAP were not significantly changed; CI, SVI and SWI presented, respectively, a significant 31.6, 55.1 and 72% increment, which peaked 48 hours after amrinone infusion. Concomitantly RAP, PAP, PWP, SVR, PVR and TPR were significantly reduced to 36.6, 22, 23.6, 9.4, 39.2 and 37.7% of the basal values, respectively. Two and 4 hours after amrinone withdrawal, hemodynamic changes similar to those observed acutely, were still present. Diuresis increased from 58.25 ml/hr to 113.18 ml/hr after 24 hours (+95%) and to 88.9 ml/hr (+53%) after 48 hours.(ABSTRACT TRUNCATED AT 250 WORDS)