Dopamine-Induced Alterations in Coronary Hemodynamics in Dogs

The effect of intravenous infusions of dopamine on left circumflex coronary blood flow and myocardial oxygen consumption in doses ranging from 5 to 100 µg/kg/min was studied in 17 open-chest dogs anesthetized with chloralose. Flow was measured with an electromagnetic flowmeter. Dopamine caused a progressive and linear increase of coronary flow that was proportional to increases in myocardial oxygen consumption up to a dose of 80 µg/kg/min; at this dose, the increase over control was 365% (28 to 129 ml/min). These changes accompanied marked increases in stroke volume, left ventricular dP/dt, and mean systolic ejection rate. Mean aortic pressure and heart rate changed little at doses below 10 µg/kg/min, but increased steadily with doses over the range of 15 to 40 µg/kg/min. Dopamine is a potent stimulator of coronary blood flow and myocardial contractility. The fact that the increased coronary flow was proportional to increases in myocardial oxygen consumption indicates that the induced coronary vasodilation is secondary to increased myocardial oxygen demands, rather than the result of primary coronary vasodilation.