Assessment of Myocardial Viability in Patients With Previous Myocardial Infarction by Using Single-Photon Emission Computed Tomography With New Metabolic Tracer: [123I]-16-Iodo-3-Methylhexadecanoic Acid (MIHA): Comparison With the Rest-Reinjection Thalli

Objectives. We compared the ability of rest single-photon emission computed tomography (SPECT) with [123I]-16-iodo-3-methylhexadecanoic acid (MIHA) and the thallium-201 (Tl-201) rest-reinjection technique to detect myocardial viability after infarction. Background. After myocardial infarction, MIH frequently shows increased uptake in the areas with exercise Tl-201 defects (mismatch), even in patients with an irreversible Tl-201 reinjection defect. Whether such increased uptake is indicative of ischemic but viable myocardium is not known. Methods. We studied 38 patients who 1) underwent exercise SPECT Tl-201 with rest-reinjection and rest SPECT with MIH before undergoing percutaneous transluminal coronary angioplasty (PTCA) of an infarct-related coronary artery, and 2) were found to have successful revascularization at follow-up angiography. The relation between SPECT results before PTC and subsequent improvement in left ventricular wall motion was assessed. Results. mismatch was evident before PTC in 51 of 76 infarct-related segments and correlated with subsequent improvement in wall motion (overall accuracy 71%), even for the 27 segments whose exercise defects remained irreversible after Tl-201 reinjection (overall accuracy 81%). The finding of mismatch clearly enhanced the results provided by the finding of ≥50% Tl-201 uptake as determined at redistribution (p < 0.05), but not as determined at reinjection, although there was trend toward better specificity for the findings of mismatch. Conclusions. MIH is an efficient marker of viability inside exercise-underperfused areas after infarction, even in patients with irreversible Tl-201 reinjection defects. Assessment by conventional SPECT of mismatch between results obtained with metabolic tracer (MIHA) and flow tracer analyzed at exercise (Tl-201) as marker of myocardial viability is promising are of research.