Effect of dopexamine hydrochloride in the early stages of experimental myocardial infarction and comparison with dopamine and dobutamine.

The effect of dopexamine hydrochloride on myocardial performance, and on the susceptibility of the myocardium to generation of arrhythmias during the development of myocardial infarction has been compared with dopamine and dobutamine in 2 experimental models of myocardial ischemia. All 3 agents improved cardiac function in the presence of a developing infarct. Dopamine and dobutamine increased myocardial contractility (left ventricular dP/dt and left ventricular dP/dt/P), which would be expected to increase oxygen consumption and thus further compromise the ischemic myocardium. Dopexamine hydrochloride, however, improved cardiac function mainly by reducing afterload. The infusion of dopamine and dobutamine resulted in a high (100%) incidence of ventricular arrhythmias compared with only 63% with dopexamine hydrochloride. The effects of these agents on early ischemic arrhythmias after coronary artery ligation in anesthetized rats were also studied. Dopexamine hydrochloride reduced the incidence and severity of arrhythmias in the early stages of ischemia: At a dose of 0.25 micrograms/kg/min, the total number of ectopic beats was reduced to 375 +/- 175, from 1,250 +/- 330 in control rats (p less than 0.05). Dopexamine hydrochloride also significantly reduced mortality from ventricular fibrillation and there was a slight reduction in the incidence and duration of ventricular tachycardia and fibrillation.