In patients with non-insulin-dependent diabetes mellitus (NIDDM), FDG PET imaging is often problematic because of poor uptake of FDG. Different protocols have been used; however, these have not been directly compared in patients with NIDDM who have both coronary artery disease (CAD) and severe left ventricular (LV) dysfunction, for which defining viability is most relevant. The aim of this study was to better define the optimal means of FDG PET imaging, assessed by image quality and myocardial glucose utilization rate (rMGU), among 3 imaging protocols in patients with NIDDM, CAD, and severe LV dysfunction.
Methods: Ten patients with NIDDM, CAD, and severe LV dysfunction (mean ejection fraction, 29.8% +/- 7.1%) underwent dynamic FDG PET scanning using 3 different protocols: the standard protocol, consisting of oral glucose loading or a supplemental insulin bolus based on fasting glucose; the niacin protocol, consisting of pretreatment with niacin to lower free fatty acids; and the insulin clamp protocol, consisting of hyperinsulinemic euglycemic clamp. Image quality was satisfactory with at least 1 approach in 8 patients, who formed the primary analysis group.
Results: Myocardium-to-blood-pool ratios were significantly higher with the insulin clamp (standard, 1.7 +/- 1.2; niacin, 1.6 +/- 1.0; insulin clamp, 3.4 +/- 2.5 [P < 0.05 vs. standard and niacin]). Values for rMGU were higher with the insulin clamp (standard, 0.11 +/- 0.07 micromol/g/min; niacin, 0.12 +/- 0.11 micromol/g/min; insulin clamping, 0.22 +/- 0.12 micromol/g/min [P = 0.004 vs. standard and 0.07 vs. niacin]).
Conclusion: The hyperinsulinemic euglycemic clamp yielded the highest FDG PET image quality and the highest rMGU in a comparison with the standard and niacin protocols in this difficult group of patients with NIDDM, CAD, and severe LV dysfunction. The hyperinsulinemic euglycemic clamp may be the preferred method for FDG PET viability imaging in this population. Larger clinical trials are needed to assess whether accuracy is greater with this approach.