Glucose metabolism in reperfused myocardium measured by [2-18F] 2-fluorodeoxyglucose and PET.

ABSTRACT

OBJECTIVE: [2-18F] 2-fluorodeoxyglucose (FDG) is widely used to trace glucose metabolism for cardiac imaging with positron emission tomography. Because the transport and phosphorylation rates differ for glucose and FDG, a lumped constant (LC) is used to correct for these differences. The effects of ischemia and reperfusion on the LC in vivo are unknown. To determine the validity of FDG as a tracer of glucose metabolism in post-ischemic myocardium in vivo, the relationship between glucose uptake (GU) and FDG metabolic rate (FDG-MR) was assessed early post-reperfusion following a transient ischemic event. METHODS: FDG metabolic rate, measured with FDG and PET, was compared to invasive measurements of substrate metabolism in reperfused and global myocardium of dogs subjected to 25 min ischemia and 2 h reperfusion. RESULTS: The FDG metabolic rate was decreased 20 +/- 4% in reperfused relative to remote myocardium. Glucose oxidation and lactate uptake were also decreased in reperfused relative to global myocardium, by 26 +/- 6% and 60 +/- 8% respectively. Glucose uptake did not differ significantly between reperfused and global myocardium. A linear correlation between FDG metabolic rate and glucose uptake was found in both reperfused and remote myocardium. Estimates of the LC from the slopes of the regression lines were similar in reperfused and remote myocardium, 1.25 and 1.44 respectively, and did not differ significantly from the LC determined in control dogs, 1.1. CONCLUSIONS: We conclude that the FDG metabolic rate continues to correlate well with glucose metabolism in reperfused myocardium. While FDG metabolic rate was modestly decreased in the absence of a significant change in glucose uptake, large alterations in the LC are not found 2 h post-reperfusion in vivo.