USING GATED TECHNETIUM-99M-SESTAMIBI SPECT TO CHARACTERIZE FIXED MYOCARDIAL DEFECTS AS INFARCT OR ARTIFACT

Perfusion-scan fixed defects may result from soft tissue attenuation, decreasing test specificity for coronary disease and myocardial infarc tion (MI). Gated Tc-99m-sestamibi SPECT may help differentiate MI from artifact since fixed defects with decreased function (wall motion and thickening) probably represent MI, whereas attenuation artifacts eith er have normal function or at least do not demonstrate markedly reduce d function. Methods: Ungated resting and gated stress Tc-99m-sestamibi SPECT was performed in 551 consecutive patients referred for evaluati on of coronary disease. From resting and summed gated stress images, 1 80 patients (33%) were identified with isolated fixed defects. Functio n of the defects was assessed subjectively from gated stress images an d results were correlated with clinical (history and/or ECG Q-waves) e vidence of MI. Results: Of 102 patients with fixed defects and clinica l MI, 98 (96%) had abnormal defect function. Of 78 patients with no cl inical MI, 18 (23%) had decreased function of the defect, possibly ind icating silent MI. In 60 of the 78 patients (77%) with no clinical MI, defect function was normal. Because most (91%) of fixed defects with normal systolic function occurred in women with anterior fixed defects (48%) or men with inferior fixed defects (43%), these were most likel y attenuation artifacts. By reclassifying patients with fixed defects and normal function as normal, patients with unexplained fixed defects (no clinical MI) decreased from 14% to 3%. Conclusion: Gating provide s a valuable adjunct to Tc-99m-sestamibi SPECT in characterizing fixed defects and potentially improving test specificity.