Cardiovascular actions of amrinone in anesthetized open-chest pigs with an acute mild stenosis in the left anterior descending coronary artery.

A 15 minute reduction of the flow in the left anterior descending coronary artery (LAD) to 50% of baseline caused a 10% decrease in cardiac output in anesthetized open-chest pigs (n = 12), together with a fall in max LV dP/dt (20%), mean arterial blood pressure (15%) and stroke volume (7%), while left ventricular filling pressure rose from 9 +/- 1 to 15 +/- 1 mmHg. The decrease in perfusion of the LAD nourished myocardium was not evenly distributed as endo-epi blood flow ratio decreased from 1.03 +/- 0.05 to 0.50 +/- 0.08. Regional myocardial wall thickening of the ischemic segment decreased from 34 +/- 6 to 7 +/- 3%, while the arterio-coronary venous differences in pH and PCO2 increased five and two fold, respectively. Subsequently, 6 animals received 1 mg X kg-1 plus 50 micrograms X kg-1 X min-1 amrinone for 10 minutes, whereas 6 other animals were treated with saline. In the following 10 minutes cardiovascular performance in the saline-treated animals did not change dramatically, although there was a tendency to further deterioration. Administration of amrinone led to a decrease in left ventricular filling pressure (30%), stroke volume (20%), cardiac output (10%) and mean arterial pressure (20%). There was also a mild positive chronotropic action (15%) and an initial positive inotropic action as indicated by an increase in max LV dP/dt (25%). The positive inotropic effect, however, was short-lasting as max LV dP/dt returned to baseline within 10 minutes after the bolus injection.(ABSTRACT TRUNCATED AT 250 WORDS)