Comparison of the effects of amrinone and dobutamine on hemodynamics and myocardial oxygen balance in dogs with experimental left ventricular failure.

The purpose of the present study was to induce left ventricular failure in anesthetized dogs by repeated ventricular fibrillation and then to determine if amrinone is effective in circulatory support by comparing the effects of amrinone and dobutamine. After the repetitive ventricular fibrillation, mean arterial pressure and stroke volume index decreased, pulmonary capillary wedge pressure (PCWP) increased, and acute left ventricular failure occurred. Thereafter, dogs were divided into the following four groups. In Group C (n = 6), normal saline was administered; in Group D (n = 6), dobutamine was administered at 7 micrograms/kg/min; and in Groups A40 (n = 6) and A80 (n = 7), amrinone was administered at 40 micrograms/kg/min and 80 micrograms/kg/min, respectively. Stroke volume index increased by 78% in Group D and 46% in both Groups A40 and A80. Pulmonary capillary wedge pressure decreased by 44% in Group A40 and 38% in Group A80, but remained unchanged in Group D. Similarly, total peripheral resistance decreased by 32% in Group A40, 29% in Group A80, but remained unchanged in Group D. These results suggest that amrinone increased cardiac output and decreased both preload and afterload. In the coronary circulation, both drugs caused direct coronary vasodilation since they increased myocardial oxygen supply in excess of the increase in myocardial oxygen demand. Neither drug produced signs of myocardial ischemia, as indicated by myocardial lactate metabolism. Amrinone should be a useful drug after open heart surgery, especially in cases where significant adverse effects of catecholamines occur or where a low-output state with increased preload and afterload exists.