Effect of prenalterol on contractility, relaxation, and filling phase in coronary artery disease patients with previous myocardial infarction.

Twelve postmyocardial infarction patients, with angiographically proven asynergic areas, but without overt cardiac failure, were treated with prenalterol intravenously, (a new cardioselective inotropic agent) at a dose of 30 micrograms/kg. The aim of this study was to test the usefulness and safety of this new drug in postmyocardial infarction patients, monitoring systolic and diastolic acute hemodynamic changes. Significant improvement in cardiac contractility was demonstrated by the increase of ejection fraction (+23%), stroke volume index (+22%), cardiac output (+41%), positive dp/dt (+82%), and Vmaxd (+39%). Left ventricular systolic, mean aortic, and mean right atrial pressure remained unchanged; a slight decrease in end-diastolic volume index (-2%) occurred. A significant increase in heart rate (from 66 +/- 7 to 85 +/- 14 beats/min), without electrocardiographic changes or subjective complaints of angina pectoris, was observed. Segmental wall motion analysis showed an improved systolic shortening in normal (from 34 to 44%) and in asynergic areas (from 10 to 18%), whereas no changes were observed in dyskinetic areas. The relaxation and filling phase also improved, as tested by negative dp/dt (+39%), time constant of relaxation (-36%), and by indices of ventricular compliance. Side effects consisted of a slight feeling of tension in two patients and a short episode of ventricular tachycardia (5 beats) in another patients. No episode of angina pectoris was observed. These results, with special emphasis on lack of exacerbation of pre-existing ischemia (although obtained in patients without evident heart failure), suggest the potential usefulness of prenalterol in acute cardiac failure, as well as postmyocardial infarction low-output syndrome.