[Myocardial scintigraphy with Tc-99m-teboroxime: its feasibility and the evaluation of its diagnostic reliability. A comparison with thallium-201 and coronary angiography].

BACKGROUND

Tc-99m-teboroxime is a new tracer for myocardial perfusion scintigraphy. Its more remarkable features are the high myocardial extraction fraction, which is well correlated with the coronary blood flow, and the extremely rapid myocardial washout. This makes it necessary to complete the image collection shortly after the injection; on the other hand, repeated scans can be easily performed by renewed Tc-99m-teboroxime administrations. The aim of the present study was to test the feasibility of Tc-99m-teboroxime imaging and to evaluate its accuracy by comparing it with thallium-201 (TI-201) scintigraphy and coronary angiography.

METHODS

The patient population included 16 male patients (mean age 57.8 +/- 6.3 years) affected by suspect effort angina and/or with signs of exercise-induced ischemia; 12 of them had history of previous myocardial infarction. They underwent effort TI-201 and Tc-99m-teboroxime myocardial scintigraphy within 48 hours; left heart catheterization and coronary angiography were performed within 5 days. Scintigraphic images were collected in 3 planar views; each projection was divided in 3 segments, with the apical one shared by all views, for a total of 7 segments/study. Tracer uptake was qualitatively assessed and graduated according to a scoring scheme (from 0 = normal through 4 = absent uptake).

RESULTS

Tc-99m-teboroxime scans could be accomplished without major problems in all subjects. The image quality was comparable to TI-201 in 8 patients and poorer in the remaining 8. Coronary angiography showed 50% obstructions in 15 patients; of them 1 subject had a normal scintigraphic pattern with both TI-201 and Tc-99m-teboroxime. The presence of previous infarction was recognized by both tracers in the 12 patients with infarct history. The number of abnormal segments and the uptake score were not significantly different in the Tc-99m-teboroxime rest and in the TI-201 redistribution images (segments: 2.8 +/- 1.4 vs 2.8 +/- 1.6; score: 5.6 +/- 4.2 vs 6 +/- 4.5). The diagnosis of effort ischemia was made in 13 patients with Tc-99m-teboroxime and in 12 patients with TI-201. The number of abnormal segments in the exercise Tc-99m-teboroxime and TI-201 myocardial scintigraphy was not significantly different (3.3 +/- 1.3 vs 3.3 +/- 1.5); on the contrary the defect score was significantly higher with Tc-99m-teboroxime than with TI-201 (9.5 +/- 4.3 vs 8.4 +/- 4.6, p < 0.03). Therefore the ischemic score (exercise defect score minus rest defect score) of Tc-99m-teboroxime was significantly higher than that of TI-201 (3.9 +/- 2.8 vs 2.4 +/- 2.2, p < 0.02). The two tracers gave comparable results in terms of recognition of patients with one-vessel or multi-vessel coronary artery disease.

CONCLUSIONS

Planar myocardial scintigraphy with Tc-99m-teboroxime can be performed without major problems. In terms of clinical reliability the results are comparable to those of TI-201 scans. On the other hand, taking into account the poor image quality of Tc-99m-teboroxime scintigraphy, it is still impossible to predict its future role in the radionuclide imaging of coronary artery disease.