Time course evaluation of myocardial perfusion after reperfusion therapy by 99mTc-tetrofosmin SPECT in patients with acute myocardial infarction.

UNLABELLED Myocardial perfusion imaging with 99mTc-labeled agents immediately after reperfusion therapy can underestimate myocardial salvage. It is also conceivable that delayed imaging is useful for assessing the risk area. However, to our knowledge, very few studies have sequentially evaluated these image changes. We conducted 99mTc-tetrofosmin (TF) and 123I-beta-methyl-p-iodophenylpentadecanoic acid (BMIPP) SPECT before and after reperfusion to treat acute myocardial infarction and quantified changes in TF myocardial accumulation and reverse redistribution. METHODS Seventeen patients with a first myocardial infarction underwent successful reperfusion. We examined SPECT images obtained at the onset (preimage), those acquired 30 min (early image) and 6 h (delayed image) after TF injection, and images acquired 1, 4, 7, and 20 d after reperfusion (post-1-d, post-4-d, post-7-d, and post-20-d image, respectively). We also examined BMIPP SPECT images after 7 +/- 1.8 d (BMIPP image). Polar maps were divided into 48 segments to calculate percentage uptake, and time course changes in segment numbers below 60% were observed as abnormal area. Moreover, cardiac function was analyzed by gated TF SPECT on 1 and 20 d after reperfusion. RESULTS In reference to the abnormal area on the early images, the post-1-d image was significantly improved compared with the preimage (P < 0.01) as was the post-7-d image compared with the post-1-d and post-4-d images (P < 0.05, respectively). However, post-20-d and post-7-d images did not significantly differ. Therefore, the improvement in myocardial accumulation reached a plateau 7 d after reperfusion. On the other hand, the abnormal area on the delayed images was significantly greater (P < 0.01) compared with that on the early images from 4 to 20 d after reperfusion, as the value was essentially constant. The correlations of the abnormal area between the preimage and the post-7-d delayed image, the preimage and the BMIPP image, and the post-7-d delayed image and the BMIPP image were very close (r = 0.963, r = 0.981, and r = 0.975, respectively). Gated TF SPECT revealed that the left ventricular ejection fraction was not significantly different (P = not significant) between 1 and 20 d after reperfusion, but regional wall motion was significantly different after reperfusion (P < 0.05). CONCLUSION These results suggest that the interval between reperfusion therapy and TF SPECT should be 7 d to evaluate the salvage effect and that TF delayed and BMIPP images are both useful in estimation of risk area.