[Quantitative assessment of myocardial viability by thallium-201 reinjection with SPECT: comparative studies with resting image in myocardial infarction].

Exercise-stress thallium (Tl) scintigraphy is a reliable diagnostic tool for evaluating the reversibility of injury to the myocardium; however, overestimation of infarcted volume has been considered as a clinical limitation, both in recent and in old myocardial infarctions. To reveal the clinical efficacy of reinjection modification, infarcted and ischemic myocardium were quantitatively evaluated by stress, reinjection, and resting image with 201Tl SPECT in 43 patients with myocardial infarction. A quite significant correlation was found in severity scores from reinjection and resting images (87 +/- 12 vs. 81 +/- 10, r = 0.85, p < 0.001), these were significantly lower than the scores from post-exercise (124 +/- 13) and 4-hour delayed (103 +/- 11) images. The fractions of reversible ischemic myocardium predicted by reinjection and resting images also correlated with each other (r = 0.55, p < 0.05) and were significantly larger than those from 4-hour delayed images. Furthermore, the degree of redistribution of myocardial perfusion observed in reinjection image showed a significant positive linear correlation with improved myocardial perfusion after coronary revascularization (r = 0.80, p < 0.001), while that from the 4-hour delayed image did not. These results suggest that the severity score of thallium reinjection method is useful for quantifying both labile and non-labile myocardium after myocardial infarction and contributes to predicting the effect of coronary revascularization therapy.