Demonstration of differential post-stenotic myocardial technetium-99m-teboroxime clearance kinetics after experimental ischemia and hyperemic stress

The clearance kinetics of the perfusion tracer ^99mTc-teboroxime were evaluated in post-stenotic and normal myocardium using dynamic planar gamma camera imaging in pre-instrumented dogs in the control state (n = 9) and following total occlusion (2 min), pharmacologic stress with adenosine [80 and 160 μg/kg/min] or dipyridamole, and rapid atrial pacing (220/min). Technetium-99m-teboroxime clearance in normal myocardium was accelerated by adenosine and by dipyridamole compared to the control state (8.9 ± 1.1 and 9.3 ± 1.9 min versus 11.9 ± 1.8 min; p < 0.05). Post-stenotic ^99mTc-teboroxime clearance half-time was most significantly prolonged compared to nonoccluded contralateral perfusion zones by 160 μg/kg/min adenosine stress (11.2 ± 3.7 versus 6.3 ± 1.5 min) and by complete coronary occlusion (12.1 ± 3.3 versus 6.6 ± 1.2 min; both p < 0.05). Differential tracer clearance from post-stenotic versus nonoccluded zones produced quantitative evidence of relative defect 'redistribution' in 71% of maximal stress studies at a mean of 8.8 ± 2.5 min postinjection. Sensitivity, specificity, and diagnostic accuracy of prolonged regional ^99mTc-teboroxime clearance rates for post-stenotic perfusion abnormalities were 62%, 100% and 81% in maximal stress studies. Future clinical trials of exercise and nonexercise stress ^99mTc-teboroxime imaging should consider these kinetic characteristics and examine the correlates of perfusion defect 'redistribution.'