Background- To assess the value of 24-hour redistribution imaging after 201Tl reinjection for the detection of myocardial viability, we compared the results of 201Tl reinjection imaging with those obtained 24 hours after reinjection.
Methods- In total, 35 patients aged 57±8 years (mean±SD) who showed one or more persistent perfusion defects on stress reinjection images after myocardial infarction were assessed for myocardial viability. After pharmacological stress and 4-hour reinjection imaging, 25 patients who showed non-viable segments at reinjection image underwent 24-hour redistribution imaging. The stress, reinjection, and 24-hour redistribution images were analyzed quantitatively. Criteria for viability definition were:1) segments which showed at least 50% uptake of peak activity of normal regions at stress phase and 2) segments with less than 50% uptake at stress image which showed at least 20% redistribution at the later phases.
Results- Of the 102 abnormal myocardial regions on the stress images, 19 segments at reinjection images and another 17 segments at 24-hour redistribution images demonstrated redistribution. On the other hand, 24-hour imaging showed viability in 17 out of 83 segments (20.4%), which were considered non-viable regions at reinjection image, occurring in 8 out of 25 patients.
Conclusion: In stress reinjection protocol by 201Tl, 24-hour redistribution imaging is proposed to be performed in patients who show significant non-viable myocardial tissue at 4-hour reinjection imaging for a better recognition of viable myocardium