Haemodynamic effects of prenalterol in acute myocardial ischaemia in open chest pigs.

The haemodynamic effects of prenalterol, a new sympathomimetic agent, have been studied in anaesthetized open-chest pigs with acute myocardial ischaemia provoked by left anterior descending coronary artery ligation. A group of eight animals was infused with saline and served as control (C). In both groups the ligation of the left anterior descending coronary artery determined a significant (P less than 0.05) reduction of aortic flow, maximum left ventricular (LV) dp/dt with no changes in heart rate. The infusion of a first dose of 30 micrograms/kg of prenalterol restored the depressed haemodynamics but increased significantly the heart rate in the prenalterol group while the saline infused group did not show any significant changes. The haemodynamic effects of prenalterol were still evident 25 min after the infusion. The subsequent administration of a second dose of 60 micrograms/kg of prenalterol resulted in a further improvement of the aortic flow, LV dp/dt and heart rate which reached values higher than in the basal condition. The positive inotropic effect was not associated with changes in stroke volume, therefore the increase in aortic flow was essentially due to an increase of the heart rate. It is concluded that prenalterol is a powerful inotropic agent in acutely infarcted animals. Its action on aortic flow appears to be related to an increase in heart rate in contrast to some previous observations.