Dobutamine modifies myocardial infarct size through supply-demand balance

We investigated dobutamine effect on infarct size during permanent coronary artery occlusion in dogs. The coronary artery of closed-chest dog was embolized by a 2.5-mm Teflon bead. Regional flow was measured 8 min after embolization with microspheres and, in drug-treated animals, again 20 min after starting dobutamine infusion (10 micrograms.kg-1.min-1 for 5 h immediately after the first microsphere measurement). The percent of the ischemic region progressing to infarct was determined 48 h later in each animal. Percent necrosis in the control group correlated closely with collateral flow to the epicardial one-third of the ischemic zone normalized against flow to the corresponding layer in the nonischemic zone. This flow should reflect an index of supply (collateral flow) and demand (flow to the nonischemic region determined by autoregulation). Percent necrosis in the drug-treated group did not correlate with normalized collateral flow measurement made before drug infusion, indicating that dobutamine had modified the course of infarction. Percent necrosis correlated well with normalized collateral flow measured during drug infusion, and that relationship was not different from that in the control group. Dobutamine increased infarct size over that expected from the predrug flow measurement in some dogs and reduced it in others. In all cases, however, the drug effect on infarct size was clearly reflected in normalized collateral flow measurement during drug infusion. Percent necrosis correlated with absolute collateral flow but less closely than with the normalized one.(ABSTRACT TRUNCATED AT 250 WORDS)