Haemodynamic dose-response effects of intravenous amrinone in left ventricular failure complicating acute myocardial infarction.

The haemodynamic dose-response effects of intravenous amrinone were measured in 16 male patients, aged 40-65 years, with radiographic and haemodynamic evidence of left ventricular failure 4-18 h after acute myocardial infarction. After a l-h control period to confirm stable haemodynamic baseline variables, patients were randomised to either low-dose (200-400-800 micrograms/kg/h) or high-dose (800-1600-3200 micrograms/kg/h) intravenous amrinone. Each of the three infusions was given consecutively over 30 min (total infusion time 90 min) in each group, and haemodynamic measurements were made at the end of each infusion step. No arrhythmias or other untoward side effects, including haematological changes, were observed during the infusions. In both groups, intravenous amrinone reduced the pulmonary artery-occluded pressure (PAOP) (p less than 0.01), increased the cardiac output (p less than 0.05), and reduced the systemic vascular resistance (p less than 0.05). The reductions in PAOP and systemic arterial diastolic pressure and the increase in heart rate were directly dose-related, but the changes in cardiac output and systemic vascular resistance were not. These results suggest that peripheral vasodilation, particularly of venous capacitance vessels, as well as positive inotropic stimulation, may play a role in the haemodynamic changes induced by intravenous amrinone in acute ischaemic left ventricular failure.