ASSESSMENT OF MYOCARDIAL VIABILITY AFTER TL-201 REINJECTION OR REST-REDISTRIBUTION IMAGING - A MULTICENTER STUDY

To establish the real nature of Tl-201 defects in the assessment of my ocardial viability (e.g., fixed versus reversible), Tl-201 reinjection was evaluated in a multicenter trial involving 402 consecutive patien ts with ischemic heart disease and exercise Tl-201 defects. Methods: T welve hospitals, using the same type of gamma camera and computer soft ware, adopted one of the two most widely used reinjection protocols. I n 230 patients (Group A), reinjection was performed immediately after stress-redistribution planar imaging; in 172 patients (Group B), reinj ection was performed on a separate day and followed by rest-redistribu tion imaging. The images were interpreted by three blinded observers i n a core laboratory on a five-point qualitative scale; the reproducibi lity in visual scoring was excellent. Results: Groups A and B had a si milar prevalence of myocardial segments with abnormal uptake at stress (39%, 40%), as well as with reversible (16%, 17%), partially reversib le (21%, 19%) and irreversible (63%, 64%) defects at redistribution. A fter reinjection, Tl-201 uptake improved in 27% and 36% of both partia lly reversible and irreversible defects in Groups A and B. No differen ces were found when comparing early and delayed reinjection imaging in Group B. Conclusion: This study confirms the validity of Tl-201 reinj ection in a large, unselected population, but the discordance with str ess/redistribution is less than has been previously reported for both Tl-201 reinjection protocols, the prevalence of improved segments afte r reinjection was higher with the separate day approach.