Systemic and coronary effects of intravenous milrinone and dobutamine in congestive heart failure

The effects of dobutamine and intravenous milrinone on systemic hemodynamics, coronary blood flow and myocardial metabolism were studied in 11 patients with severe congestive heart failure. Although milrinone and dobutamine similarly increased cardiac index from 1.9 ± 0.4 to 2.5 ± 0.4 liters/min per m² (p < 0.001) and from 1.9 ± 0.4 to 2.8 ± 0.8 liters/min per m² (p < 0.001), respectively, milrinone decreased left ventricular end-diastolic pressure to a greater extent than dobutamine, that is, from 26 ± 6 to 12 ± 8 mm Hg (p < 0.001) versus 26 ± 8 to 20 ± 8 mm Hg (p < 0.001). In contrast to dobutamine, milrinone significantly reduced mean systemic arterial and right atrial pressures. Dobutamine increased the first derivative of left ventricular pressure (dP/dt) from 1,013 ± 309 to 1,360 ± 538 mm Hg/s (p < 0.01) but milrinone did not. Similarly, blood flow and myocardial oxygen consumption were increased by dobutamine from 152 ± 87 to 187 ± 118 ml/min (p < 0.05) and from 17.7 ± 10.9 to 21.5 ± 14.9 ml O₂/min (p < 0.05), respectively, but were unchanged by milrinone. Both drugs significantly decreased coronary vascular resistance and myocardial oxygen extraction but did not change myocardial lactate extraction. Thus, dobutamine and milrinone produce similar improvement in cardiac index. However, dobutamine increases myocardial oxygen consumption, whereas milrinone does not. This difference can probably be explained by the substantial vasodilating properties of milrinone.