QUANTITATIVE-ANALYSIS OF DEFECT REVERSIBILITY AFTER IMMEDIATE AND STANDARD TL-201 REINJECTION

Immediate reinjection of Tl-201 after exercise imaging has been propos ed as a time-saving approach for the accurate distinction between isch aemic and scarred myocardium. However, with this procedure, defect rev ersibility may be underestimated due to the high level of residual Tl- 201 activity in normally perfused myocardium at the time of reinjectio n. The aim of this study was to determine whether the detection of def ect reversibility is hampered by a shortening of the time interval bet ween exercise and reinjection. In 53 patients, Tl-201 was injected at the point of maximal exercise. In 26 patients, Tl-201 was reinjected i mmediately after exercise imaging (Group I); in 27 patients, Tl-201 wa s reinjected after 3 h redistribution imaging (Group II). In all patie nts (424 myocardial segments), three-view planar images were analysed quantitatively. Changes in myocardial activity after 3 h redistributio n and reinjection were compared with the post-exercise images. In norm al segments, the relative change in Tl-201 activity after reinjection was 8.8 +/- 19.9% in Group I and -19.7 +/- 19.5% in Group II (P < 0.05 ). In Group I, persistent defects showed a relative change of 14.3 +/- 25.1% and reversible defects a relative change of 36.3 +/- 42.6% (P < 0.05). In Group II, persistent defects showed a relative change of -1 5.1 +/- 18.3% and reversible defects a relative change of 2.4 +/- 25.2 % (P < 0.05). Our results indicate that shortening the time interval b etween exercise and reinjection has no effect on the detection of isch aemia.