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 r egional differences in glucose uptake as measured by positron emission tomography (PET). Methods: The metabolic rate of glucose uptake withi n the myocardium can be assessed with the glucose analog F-18-fluorode oxyglucose (FDG). Stunning was induced in 14 anaesthetised pigs by par tially occluding the left anterior descending coronary artery (LAD) fo r 20 min (>80% flow reduction). The metabolic rate of glucose uptake w as 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 con stant intravenous infusion of dobutamine (4 mu g.kg(-1).min(-1)). Resu lts: 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 p ostischaemic LAD region of group 1, the metabolic rate of glucose upta ke was significantly lower than the non-LAD region (0.11(0.08) and 0.4 3(0.33) mu mol.min(-1).g(-1) respectively). In group 2, dobutamine ind uced 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.mi n(-1).g(-1); p<0.05) within the postischaemic LAD region. Despite recr uitment of function and oxygen consumption in group 2, the metabolic r ate 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 post ischaemic changes in oxygen consumption and wall thinning. This suppor ts the contention that after stunning, non-glucose substrates play an important part in maintaining energy expenditure during catecholamine stimulation.