IS THERE ANY ADVANTAGE TO THE ACQUISITION OF 24-HOUR THALLIUM IMAGES,IN THE PRESENCE OF PERSISTENT PERFUSION DEFECTS AT 4 H AFTER REINJECTION

We determined the incidence of delayed 24-h reversibility post thalliu m-201 reinjection and imaging at 4 h, as well as the prognostic and si gnificance of such delayed reversibility. We studied 46 consecutive pa tients with persistent thallium-201 perfusion or incompletely reversib le single-photon emission tomography (SPET) perfusion defects acquired within 10 min after reinjection performed 4 h after stress. In 38 of 46 patients (82%) 24-h images showed no further reversibility beyond t he post-reinjection 4-h study (group A). Eight of 46 patients (17%) de monstrated reversibility on 24-h imaging (group B). Of these eight, th ree patients showed no improvement compared with the post-stress image s, with a mean perfusion score of the abnormal segments of 1.25+/-0.50 on the 4-h images, and of 3.00 on the 24-h images, where normal is 4. Four patients presented with nine mixed regions. Four of these region s showed an improvement in the mean perfusion score of 2.50+/-0.58 on 4- and 24-h images. Two of them, with moderate/severe defects, demonst rated complete reversibility at 4-h post-reinjection imaging. In addit ion, five other regions presented no improvement at 4-h imaging, but s howed an improvement in the mean perfusion score from 0.80+/-0.84 at 4 -h to 3.30+/-0.89 at 24-h imaging. Two of these regions in one patient showed a severe perfusion score of 0 at 4 h, and complete reversibili ty at 24 hours, with a mean score improvement of 4. Another patient ha d three severe perfusion defects; two of them redistributed partially at 4 h and completely at 24 h The remaining segment with a perfusion s core of 0 at 4 h. presented complete reversibility with a score of 4 a t 24 h. Two (4%) patients revealed significant reversibility at 24 h i n a region that was severely underperfused after post-reinjection imag ing at 4 h. Among group B patients, 75% (6/8) had recent acute ischemi c syndrome, compared with only 13% (5/38) in group A (P = 0.001), Amon g 11 patients with unstable angina, six (55%) had evidence of delayed 24-h reversibility, compared with 2 of 35 (6%) patients without clinic ally acute ischemia (P = 0.001). On follow-up, there were seven (17%) cardiac deaths among the 38 group A patients but three (38%) among the eight group B patients (P = 0.3), These findings suggest that althoug h the presence of delayed 24-h (TI)-T-201, post-reinjection reversibil ity is infrequent, it has potential clinical importance. Thus, delayed 24-h imaging should be considered in the context of unstable angina o r other acute coronary syndromes.