Effects of denopamine (TA-064), a new positive inotropic agent, on myocardial oxygen consumption and left ventricular dimension in anesthetized dogs.

We compared the effects of denopamine (TA-064) and isoproterenol on hemodynamics, myocardial oxygen consumption and the left ventricular (LV) dimension in halothane-N2O anesthetized dogs. Denopamine (0.25-1 micrograms/kg/min, i.v., infusion X 15 min) produced a maximum increase in LV dp/dtmax by 64% of the control, without affecting aortic pressure significantly. Doses of isoproterenol (0.01-0.04 micrograms/kg/min, i.v., infusion X 15 min) were selected to produce a positive inotropic action similar to that of denopamine. Denopamine produced significantly less increasing effects in heart rate, cardiac output and myocardial oxygen consumption and had more reducing effects in LV internal diameter than isoproterenol, while isoproterenol tended to produce a more potent increase in coronary blood flow, but a smaller decrease in LV end-diastolic pressure than denopamine. PQ interval was similarly reduced. Denopamine caused no substantial increase in myocardial oxygen consumption at a lower dose, at which LV dp/dtmax was significantly increased. A weak effect of denopamine on myocardial oxygen consumption may result partly from a weak positive chronotropic effect and partly from a reduction of preload and cardiac size.