A simplified intravenous glucose loading protocol for fluorine-18 fluorodeoxyglucose cardiac single-photon emission tomography
UNLABELLED Diabetes mellitus (DM) is one of several factors influencing the assessment of myocardial viability using fluorine-18 fluorodeoxyglucose (FDG) PET. METHODS To compare the myocardial glucose metabolism of normal subjects to patients with DM, we performed a quantitative FDG study during insulin clamp, oral glucose loading and fasting in nine normal volunteers and eight patients with noninsulin-dependent DM (NIDDM). RESULTS During oral glucose loading, myocardium-to-background (MB) ratio remarkably deteriorated in NIDDM patients compared with normals because of high plasma glucose and low serum insulin. Myocardial glucose utilization (MGU) rates in NIDDM patients were also lower than those in normal volunteers. MB ratio of FDG remarkably improved with insulin clamp in NIDDM patients compared with oral glucose loading. MGU rates during insulin clamp were still slightly lower than in the normal volunteers despite low plasma glucose and adequate plasma insulin. CONCLUSION The insulin clamp method may be very useful in NIDDM patients for improved myocardial FDG uptake compared to oral glucose loading or fasting, but slight decreases in MGU rates during insulin clamp in NIDDM patients may be because of insulin resistance (GluT4 abnormality).