Response to incremental doses of dobutamine early after reperfusion is predictive of the degree of myocardial salvage in dogs with experimental acutemyocardial infarction

OBJECTIVES We sought to determine whether the inotropic response to dobutam ine might be useful for estimating the extent of viable myocardium soon aft er reperfusion. BACKGROUND Early identification of viable myocardium in the presence of sev ere left ventricular dysfunction after reperfusion is important for clinica l decision making. METHODS Nine open-chest dogs had left anterior descending coronary artery o cclusion for 40 to 180 min, followed by gradual reperfusion. The systolic t hickening response to incremental dobutamine doses was measured with ultras onic crystals and regional flow by microspheres. RESULTS Dogs were divided into two groups based on triphenyl tetralozium ch loride infarct size (group 1: 9.3 +/- 3.0% risk area; group 2: 51.1 +/- 4.8 %). In group 2 dogs with larger infarcts, regional flow during peak dobutam ine was lower than it was in group 1 in endocardial (1.15 +/- 0.22 vs. 2.64 +/- 0.33 mL.min(-1).g(-1)) and midwall (1.47 +/- 0.32 vs. 2.92 +/- 0.36 mL .min(-1).g(-1)) layers, and endocardial flow in group 2 failed to increase from baseline (0.96 +/- 0.07 vs. 1.15 +/- 0.22 mL.min(-1).g(-1)). Group 1 d ogs demonstrated a dose dependent increase in systolic thickening with dobu tamine versus a blunted response in group 2. The inotropic response to only 10 mu g.kg(-1).min(-1) of dobutamine was predictive of the degree of myoca rdial salvage. CONCLUSIONS In the early postischemic stunning phase of reperfusion, the in otropic response to dobutamine is predictive of the degree of myocardial sa lvage and ultimate infarct size. The ability to distinguish between stunned versus necrotic myocardium early after reperfusion was most likely due to the presence of subendocardial flow reserve during dobutamine in dogs with predominantly salvaged myocardium. (J Am Coll Cardiol 2000;35:1960-8) (C) 2 000 by the American College of Cardiology.