EFFECTS OF DOBUTAMINE STIMULATION ON REGIONAL MYOCARDIAL GLUCOSE-UPTAKE POSTSTUNNING AS MEASURED BY POSITRON EMISSION TOMOGRAPHY

Objectives: The aim was to determine whether dobutamine stimulation of energy expenditure within the postischaemic myocardium would affect regional differences in glucose uptake as measured by positron emission tomography (PET). Methods: The metabolic rate of glucose uptake within the myocardium can be assessed with the glucose analog F-18-fluorodeoxyglucose (FDG). Stunning was induced in 14 anaesthetised pigs by partially occluding the left anterior descending coronary artery (LAD) for 20 min (>80% flow reduction). The metabolic rate of glucose uptake was determined 2 h after reperfusion in the LAD and non-LAD regions in two groups: without (group 1; n = 7) and during (group 2; n = 7) a constant intravenous infusion of dobutamine (4 mu g.kg(-1).min(-1)). Results: In all pigs, stunning reduced systolic shortening from 16(SD 4)% to 5(5)% (p<0.05) and slightly lowered myocardial oxygen consumption, from 3.18(1.21) to 2.67(0.93) mu mol.min(-1).g(-1) p = 0.08). In the postischaemic LAD region of group 1, the metabolic rate of glucose uptake was significantly lower than the non-LAD region (0.11(0.08) and 0.43(0.33) mu mol.min(-1).g(-1) respectively). In group 2, dobutamine induced a sustained increase in both fractional shortening (7(4)% to 16(5)%; p<0.05) and oxygen consumption (2.34(0.94) to 4.53(1.52) mu mol.min(-1).g(-1); p<0.05) within the postischaemic LAD region. Despite recruitment of function and oxygen consumption in group 2, the metabolic rate of glucose uptake was similar to that of group 1 (0.11(0.09) and 0.40(0.28) mu mol.min(-1).g(-1) in LAD and remote regions respectively). Conclusions: In this pig model of stunning, uptake of FDG was lower in stunned compared with remote myocardium and was independent of postischaemic changes in oxygen consumption and wall thinning. This supports the contention that after stunning, non-glucose substrates play an important part in maintaining energy expenditure during catecholamine stimulation.