Metabolic myocardial viability assessment with iodine 123-16-iodo-3-methylhexadecanoic acid in recent myocardial infarction: comparison with thallium-201 and fluorine-18 fluorodeoxyglucose.

The best test presently available to ascertain residual viability within an infarct-related area involves the use of fluorine-18 fluorodeoxyglucose (FDG) to detect the persistence of some cellular metabolism. Rest reinjection of thallium-201 is a less accurate alternative but is easy to perform. Iodinated fatty acids, which are used with standard gamma cameras, are proposed as markers of cellular metabolism. This study was performed to assess the value of 16-iodo-3-methylhexadecanoic acid (MIHA) as a marker of the residual cellular metabolism by comparison with FDG in patients with a recent myocardial infarction, and to evaluate its contribution compared with the 201Tl stress-redistribution-reinjection technique. Stress-redistribution-reinjection 201Tl imaging, rest MIHA imaging and glucose-loaded FDG imaging were performed in 22 patients with recent myocardial infarction. Out of the 628 myocardial segments obtained from the left ventricular analysis, 400 were hypoperfused (relative uptake <0.75 of maximum uptake on stress 201Tl imaging), 177 of which were severely hypoperfused (relative uptake <0.50). Receiver operating characteristic (ROC) curves for predicting metabolic myocardial viability with FDG were derived from the results in respect of (a) 201Tl activity during exercise, redistribution and reinjection and (b) MIHA uptake, using the two FDG thresholds most commonly considered to define metabolic viability (0.50 and 0.60). Analysis of the 400 hypoperfused segments demonstrated that 201Tl reinjection was the most accurate test in predicting the presence of myocardial viability (area under the ROI curves=0.85 and 0.86 at the 0.50 and 0.60 FDG thresholds, respectively; P<0.05 vs other tests). The global predictive values of MIHA and 201Tl reinjection were, respectively, 0.87 and 0.89 at the 0.50 FDG threshold (NS), and 0.82 and 0.87 at the 0.60 FDG threshold (NS). When only the 177 severely hypoperfused segments were considered, 201Tl reinjection remained the most accurate test (accuracy 0.84 at the 0.50 FDG threshold and 0.82 at the 0.60 FDG threshold), while the accuracy of MIHA decreased significantly (0.78 at the 0.50 FDG threshold and 0.73 at the 0.60 FDG threshold, P<0.05 vs 201Tl reinjection). In all circumstances, MIHA was less specific than 201Tl reinjection for the detection of metabolic viability. In conclusion, in patients with recent myocardial infarction, MIHA accurately detects the persistence of metabolic viability, but is not superior to 201Tl.