The effect of dobutamine on cardiac oxygen balance, regional blood flow, and infarction severity after coronary artery narrowing in dogs.

We compared the acute effects of dobutamine and isoproterenol on cardiac O, balance and regional blood flow (studied with microspheres) in eight male beagles with a narrowed left anterior descending coronary artery (LAD). The two drugs similarly increased cardiac contractility, output, and oxygen consumption. However, unlike isoproterenol, dobutamine did not accelerate heart rate or markedly lower peripheral resistance. Also unlike isoproterenol, dobutamine augmented blood flow in regions supplied by the LAD and improved oxygen balance, as indicated by significant increases in coronary sinus Po2, oxygen supply-consumption ratio, and lactic acid consumption. To determine whether dobutamine would contain infarction, we continuously infused it or saline in 24 beagles for 24 hours immediately after LAD constriction. Then, 1-3 days after LAD constriction, we assessed the infarction. In 11 of 12 dogs treated with dobutamine, infarctions could not be detected by gross examination or the distribution of microspheres, and microscopic lesions were minimal. In contrast, 10 of 12 dogs treated with saline had gross transmural infarctions, an absence of microspheres in the region supplied by the LAD, and marked microscopic damage. Therefore, prompt and persistent treatment with a powerful inotropic agent, used at doses low enough to avoid chronotropic and vascular side effects, may contain rather than extend myocardial infarction by increasing the supply of oxygen more than it increases the requirement for oxygen.