Rapid redistribution of teboroxime.

Teboroxime, a new technetium-99m-labeled myocardial perfusion tracer, possesses rapid myocardial kinetics. Whereas this agent is routinely imaged after separate stress and rest injections, experimental data suggest that teboroxime may rapidly redistribute in the myocardium. Accordingly, we assessed 68 exercise teboroxime scintigrams in which immediate poststress, early delay (5 minutes) and rest images were acquired. Studies were categorized visually as ischemia, infarct or normal based on conventional stress-rest comparison. They were then evaluated for rapid teboroxime redistribution by comparing the stress and early delay images. Quantitative analysis was then performed on 537 myocardial segments. Segments were grouped as ischemia, infarct or normal based on stress-rest comparison, and the degree of normalization of stress-induced defects in the early delay images was determined for each group. Rapid teboroxime redistribution was observed in 20 of 46 scintigrams (48%) considered ischemic, and in 2 of 7 and 2 of 15 scintigrams deemed infarct and normal, respectively. The mean segmental intensity ratio (defined relative to the opposite segment) improved from 0.79 at stress to 0.88 at early delay (p < 0.005) in the group with ischemia and from 0.83 to 0.87 in the group with infarction. The most likely explanation for rapid redistribution of teboroxime is differential washout from the myocardium between areas of disparate flow. It is concluded that rapid redistribution of teboroxime occurs within 5 minutes of a stress injection, giving rise to potentially useful clinical information. Thus, teboroxime imaging should be completed expeditiously to detect areas of relative hypoperfusion.