Objective: To assess the relative capacity of thallium-201 reinjection (RI) and redistribution (RD) for detection of reversibility in patients after myocardial infarction.
Design: We prospectively studied patients referred to myocardial scintigraphy for viability evaluation with stress, redistribution and reinjection images.
Methods: Patients were studied with thallium-201 SPECT using three imaging acquisitions--stress, redistribution three to four hours later and reinjection 30-60 minutes after a second injection of thallium under nitroglycerin effect. Thallium uptake was classified in a 0 to 4 intensity scale in each of 13 myocardial segments and a score obtained. Reversibility was classified as "definite" if the increase in thallium uptake was > or = 2 in a myocardial segment and as "possible" if the increase was one.
Patients: We studied 44 patients with previous myocardial infarction.
Results: The perfusion score after stress was 37.3 +/- 6.0, improving to 39.8 +/- 6.7 after redistribution and to 43.6 +/- 7.6 after reinjection (p < 0.02 between RD and RI). RD identified reversibility in 38% and RI in 63% (p < 0.001) of the 232 segments with perfusion defects. RI showed reversibility in 39% (definite in 25% and possible in 14%) of the 137 fixed perfusion defects in RD. For the detection of reversibility RI was superior to RD in all sub-groups analyzed. We found a relationship the degree of collateral circulation in the infarct related artery and the amount of reversibility in the infarcted area.
Conclusions: These data suggest a clear superiority of reinjection over redistribution in thallium-201 scintigraphy for the detection of reversibility of perfusion defects after myocardial infarction, and must probably be considered as a routine procedure for myocardial viability assessment.