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EXPERIMENTAL STUDIES

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

^a Experimental Cardiology Laboratory, Cardiovascular Division, Department of Medicine, University of Virginia Health System, Charlottesville, Virginia, USA

Manuscript received July 26, 1999; revised manuscript received December 16, 1999, accepted February 21, 2000.

Reprint requests and correspondence: David K. Glover, Cardiovascular Division, Department of Medicine, Box 158, University of Virginia Health System, Charlottesville, Virginia 22908
dglover{at}virginia.edu

OBJECTIVES

We sought to determine whether the inotropic response to dobutamine might be useful for estimating the extent of viable myocardium soon after reperfusion.

BACKGROUND

Early identification of viable myocardium in the presence of severe left ventricular dysfunction after reperfusion is important for clinical decision making.

METHODS

Nine open-chest dogs had left anterior descending coronary artery occlusion for 40 to 180 min, followed by gradual reperfusion. The systolic thickening response to incremental dobutamine doses was measured with ultrasonic crystals and regional flow by microspheres.

RESULTS

Dogs were divided into two groups based on triphenyl tetralozium chloride 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 dobutamine 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 dogs demonstrated a dose dependent increase in systolic thickening with dobutamine versus a blunted response in group 2. The inotropic response to only 10 µg·kg^–1·min^–1 of dobutamine was predictive of the degree of myocardial salvage.

CONCLUSIONS

In the early postischemic stunning phase of reperfusion, the inotropic response to dobutamine is predictive of the degree of myocardial salvage 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.

Abbreviations and Acronyms   ANOVA = analysis of variance   dP/dt = peak positive first derivative of left ventricular pressure with respect to time   LAD = left anterior descending coronary artery   LCx = left circumflex coronary artery   MI = myocardial infarction   TTC = triphenyl tetrazolium chloride

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