Rest distribution of 99mTc-MIBI in patients with coronary artery disease assessed by SPECT: comparison with the distribution of [18F]FDG assessed by PET

The distribution of 99mTc-methoxy-isobutyl-isonitrile (99mTc-MIBI), assessed by single photon emission computed tomography (SPECT) was compared to the distribution of 2-[18F]-2-deoxy-D-glucose ([18F]FDG) assessed with positron emission tomography (PET) under fasting conditions, in 21 patients with coronary artery disease (CAD) and severe left ventricular dysfunction in order to evaluate the potential usefulness of SPECT/99mTc-MIBI for the identification of viable myocardium. Stress and rest SPECT/99mTc-MIBI studies were scored based on the percent of 99mTc-MIBI uptake defined by semi-quantitative circumferential-profile analyses. PET metabolic studies with [18F]FDG under fasting conditions, were adopted as a standard of viability. The results of the comparison of 99mTc-MIBI and [18F]FDG distribution showed that among the segments with stress hypoperfusion, [18F]FDG uptake was present in 95% of the segments that had > 40% of the peak tracer uptake at the rest SPECT/99mTc-MIBI study. [18F]FDG uptake was also present, however, in 25% of the segments that had < 40% uptake at the rest SPECT/99mTc-MIBI scintigraphy. We conclude that in patients with CAD the pattern of 99mTc-MIBI distribution appears to underestimate the extent of viable myocardium but only in those regions that are very severely hypoperfused.