Myocardial stunning: a therapeutic conundrum

Dobutamine and pyruvate are two inotropic agents with different mechanisms of action. Although both agents alter postischemic myocardial dysfunction, their potential metabolic effects in the setting of in vivo myocardial stunning have not been addressed. In this study, the effects of dobutamine and pyruvate on systolic wall thickening, myocardial phosphorylation potential index, interstitial fluid adenosine level, and myocardial oxygen consumption in in vivo stunned porcine myocardium were assessed. Stunning was induced with a 10-minute occlusion of the left anterior descending coronary artery. After 30 minutes of reperfusion, pigs were treated with either intravenous dobutamine (10 micrograms/kg per minute) or intracoronary pyruvate (1 ml/min, 150 mmol/L solution, pH 7.4). Infusion of both agents resulted in a marked improvement in regional systolic wall thickening. The dobutamine effect, however, produced a marked increase in myocardial oxygen consumption and was associated with an increase in interstitial adenosine caused by myocardial de-energization, because the myocardial phosphorylation potential index ratio decreased from 0.17 +/- 0.02 to 0.09 +/- 0.02 (p < 0.05). In contrast, pyruvate enhanced myocardial energy status, because the myocardial phosphorylation potential index ratio increased from 0.20 +/- 0.03 to 0.55 +/- 0.08 (p < 0.01). These experimental findings suggest that under certain circumstances the use of beta-receptor agonists to treat myocardial stunning may be suboptimal, if not undesirable. Further investigation is warranted to determine the optimum therapy for the stunned heart.