Diagnostic value of technetium-99m-MIBI as a myocardial perfusion imaging agent: comparison of long and short intervals between rest and stress injections.

To assess the diagnostic value of technetium-99m-MIBI (99mTc-MIBI) as a myocardial perfusion imaging agent, and if rest and exercise scans could be performed on the same day, 21 patients with coronary artery disease were studied. Qualitative planar 201-thallium (201Tl) scans, coronary angiography, or both were also performed (median between studies 11 days). In 10 patients an injection of 740 mBq of 99mTc-MIBI at stress was followed by a second injection of 740 mBq at rest 24 h later (long interal) (LI). In 11 patients injection of 370 mBq at rest was followed 3 h later by an injection of 740 mBq at stress (short interval) (SI). Exercise scans were performed to similar maximal work load (LI = 6.6 +/- 1.8 METs; SI = 6.3 +/- 1.7 METs; 201Tl = 6.8 +/- 1.2 METs; p = NS) and double product (LI = 19551 +/- 7370; SI = 19900 +/- 6797; 201Tl = 19965 +/- 5282; p = NS). Overall, 99mTc-MIBI and 201Tl agreed in 92% of the patients tested and in 165 of 180 (92%) left ventricular segments in both 99mTc-MIBI protocols using short and long intervals between injections. In 15 patients with significant stenosis, 99mTc-MIBI correctly identified 13 patients (sensitivity of 87%). Thus, 99mTc-MIBI is a useful imaging agent with similar diagnostic value as 201Tl. In spite of its lack of myocardial redistribution, 99mTc-MIBI rest and exercise scans performed on the same day seem to have a similar concordance rate with 201Tl as when performed on separate days.