Effect of isoproterenol on regional myocardial perfusion and tissue oxygenation in acute myocardial infarction.

The effect of isoproterenol infusion on regional myocardial perfusion and tissue oxygenation during acute myocardial infarction was investigated in anesthetized dogs. Measurements of regional flow with radioactive microspheres and myocardial lactate and adenosine triphosphate from analysis of myocardial biopsies were compared in normal, marginal, and infarcted tissue in dogs with a ligated coronary artery. After 10 minutes of isoproterenol 0.15 microgram/Kg./minute, flow was unchanged in the marginal and infarcted regions, and, although rises occurred in most dogs, changes were inconsistent in the normal regions. In the marginal regions, tissue lactate rose by 5.6 mumoles/g (97 per cent) and adenosine triphosphate fell by 2.4 mumoles/g (46 per cent) after isoproterenol. No consistent changes occurred in the normal or infarcted regions of the dogs given isoproternol or in any regions of control dogs given saline. It is concluded that beta-adrenergic stimulation with isoproterenol increases tissue ischemia in experimental acute myocardial infarction.