Myocardial clearance kinetics of technetium-99m-teboroxime following dipyridamole: differentiation of stenosis severity in canine myocardium

Abstract

The purpose of the current study was to determine whether teboroxime clearance kinetics are useful in differentiating the severity of coronary artery flow restriction.

Methods: Groups of dogs received stenoses of the left circumflex coronary artery as follows: nine dogs received a mild-to-moderate stenosis (Group 2) and eleven dogs received severe stenoses (Group 3). In three control dogs (Group 1), there was no stenosis. Using miniature cadmium-telluride radiation detectors, myocardial teboroxime activities were continuously monitored in both the control and stenosed zones following dipyridamole infusion.

Results: A significant difference in fractional myocardial clearance between the control zones (0.69 +/- 0.01, n = 26) versus mild-to-moderate (0.61 +/- 0.06, p < 0.05, n = 9) and severe (0.57 +/- 0.03, p < 0.01 versus control, p < 0.05 versus mild-to-moderate, n = 11) flow-restricted zones was observed over a 1-hr period. Significant differences between normal and both stenosed zones became apparent after 7 min of clearance. Significant differences in myocardial clearance between mild-to-moderate and severe groups were detected within 15 min.

Conclusion: Thus, in this canine model using dipyridamole, miniature probe-determined teboroxime myocardial clearance can differentiate among normal myocardium, myocardium distal to a mild-to-moderate stenosis and myocardium distal to a severe stenosis.