Rest SPECT imaging with [123I]-16-iodo-3-methylhexadecanoic acid (MIHA) frequently shows an increased level of uptake in areas with irreversible defects on exercise 201TI SPECT. Such mismatch patterns between flow (201TI) and metabolic (MIHA) tracers might correspond to areas with ischemic but viable myocardium misidentified by 201TI imaging.
Methods: Eighty-three patients with myocardial infarction underwent exercise SPECT 201TI with rest-reinjection and rest SPECT with MIHA. Defect areas on the exercise images were reversible on MIHA but not on 201TI reinjection images that were determined visually. The presence and extent of these areas were quantified from normalized uptake values for both tracers.
Results: In areas with irreversible 201TI reinjection defects, MIHA detected exercise defect reversibility in 59% of patients. In areas with irreversible 201TI reinjection defects, the extent of visually determined defect reversibility on MIHA scans was related to the quantified extent of areas with 201TI uptake > or = 50% of normal; the correlation, however, was weak. In 86% of patients, areas with > or = 50% 201TI uptake were larger than those that were reversible on MIHA.
Conclusion: After myocardial infarction, rest SPECT with MIHA often enables visual detection of increased uptake in areas with irreversible 201TI reinjection defects.