A SIMPLIFIED INTRAVENOUS GLUCOSE LOADING PROTOCOL FOR F-18 FLUORODEOXYGLUCOSE CARDIAC SINGLE-PHOTON EMISSION TOMOGRAPHY

The myocardial uptake of fluorine-18 fluorodeoxyglucose (FDG) has emer ged as the most sensitive and specific technique for the assessment of myocardial viability. With the development of FDG single-photon emiss ion tomography (SPET) and dual head coincidence imaging, a hindrance t o the widespread clinical use of FDG cardiac imaging is the complexity of the preinjection glucose loading necessary for obtaining interpret able myocardial FDG scans. In a population of 209 patients undergoing dual-isotope single acquisition (DISA) FDG/sestamibi (MIBI) SPET, we d escribe the improvements in both image quality and time efficiency usi ng a new short, simple glucose/insulin/potassium (GIK) infusion protoc ol prior to FDG injection as compared to a conventional oral glucose l oading protocol. DISA FDG/MIBI SPET scans were performed in 111 nondia betic patients after oral loading with 50 g of glucose (group 1). Nine ty-eight consecutive nondiabetic patients were subsequently scanned fo llowing preparation with a fixed-concentration GIK infusion administer ed at a standardized rate (group 2). A three-point grading scale was u sed to assess image quality, The time to FDG injection following gluco se administration was significantly shorter for the group 2 patients ( 39.9+/-15.6 min; range 20-105 min) than for the group 1 patients (99.5 +/-30.3 min; range 56-270 min) (P<0.0001), representing a l-h decrease in patient preparation time. More of the group 1 patients (n=30; 27%) required supplemental intravenous boluses of regular insulin than did the group 2 patients (n=13; 13%) (P<0.02). There were more excellent and good quality graded images using the GIK method (group 2) than the more traditional oral loading protocol (group 1) (P<0.02). Nine of 11 1 scans (8%) in group 1 were uninterpretable, whereas only one of 98 s cans (1%) in group 2 was uninterpretable. Standardized infusion of a f ixed concentration of GIK prior to FDG administration and continued du ring myocardial FDG uptake is an effective yet simple method of obtain ing consistently good to excellent quality FDG SPET cardiac scans. It is preferable to conventional oral glucose loading due to decreased pa tient preparation time and improved image quality. The technique is sa fe and should improve both the clinical use and the cost-effectiveness of FDG SPET imaging for the identification of injured but viable myoc ardium.