[Study of myocardial viability using single-photon emission computed tomography with 201-thallium and re-injection in 4 series (early and late images].

OBJECTIVE

The present study was designed to determine whether 24-hour imaging after thallium reinjection or imaging obtained shortly after reinjection provides better results regarding reversibility of fixed perfusion defects observed in conventional stress-redistribution imaging.

PATIENTS AND METHODS

We studied 24 patients undergoing stress-redistribution thallium tomography with fixed defects (15 exercise, 6 adenosine, 3 dobutamine). All patients had coronary angiography and 17 a history of myocardial infarction. After obtaining the redistribution images, 1 mCi thallium was injected at rest, and images were acquired at 30 minutes and 24 hours after reinjection. The tomograms obtained were divided into 12 segments and analyzed quantitatively.

RESULTS

Of the 190 abnormal segments on the stress images, 53 (28%) demonstrated improved thallium uptake on redistribution images and 137 had persistent defects. Shortly after reinjection, 33 (24%) segments had improved thallium uptake and 104 had persistent defects, 29 (28%) of which showed further improvement in the 24-hour study. In patients with myocardial infarction, of the 36 fixed severe defects, 9 (25%) had improved thallium uptake shortly after reinjection, increasing activity from 36 +/- 10% to 53 +/- 8%, and 22 (61%) defects improved at 24 hours, increasing activity from 37 +/- 8% to 56 +/- 6%. Therefore, 13 irreversible segments in the short-term study after reinjection were reversible on 24-hour images.

CONCLUSION

These data indicate that 24-hour imaging after thallium reinjection provides better results regarding reversibility of fixed perfusion defects observed in conventional stress-redistribution imaging than imaging obtained shortly after reinjection.