THE ROLE OF TC-99(M)-TETROFOSMIN MYOCARDIAL PERFUSION SCINTIGRAPHY INTHE ASSESSMENT OF PATIENTS WITH PREVIOUS MYOCARDIAL-INFARCTION - A COMPARATIVE-STUDY WITH TL-201

The aim of this study was to determine the utility of Tc-99(m)-tetrofo smin cardiac imaging in patients with previous myocardial infarction a nd with significant coronary artery disease (CAD) compared with that o f Tl-201 cardiac imaging. Sixteen patients (14 males, 2 females) were studied by same-day exercise-rest Tc-99(m)-tetrofosmin imaging and exe rcise, rest and reinjection Tl-201 cardiac imaging. For each study, se miquantitative visual analysis was performed in 20 segments using a 4- point scale. The regional distribution and defect reversibility with t he two tracers were compared with the results of coronary angiography. A total of 320 segments were analysed. There was a statistically sign ificant concordance between the numbers of fixed and reversible segmen ts in both studies in myocardial segments supplied by totally occluded coronary arteries (Group 1), as well as in segments supplied by signi ficantly stenosed coronary vessels (Group 2). The exercise and rest up take of both Tc-99(m)-tetrofosmin and Tl-201 in myocardial segments su pplied by totally occluded coronary arteries with poor collateral flow was significantly lower compared with segments supplied by totally oc cluded coronary arteries with efficient collateral flow (P less than o r equal to 0.05). When the uptake of both tracers was analysed accordi ng to each major vascular territory, the mean exercise and rest uptake grades of Tc-99(m)-tetrofosmin and Tl-201 were similar. There was als o no significant difference in defect reversibility between the two tr acers. Discordant results were observed in the territory of the right coronary artery in Group 1 (mean exercise grade of Tc-99(m)-tetrofosmi n=2.26+/-0.7 and of Tl-201=1.92+/-0.8; P less than or equal to 0.001) and in Group 2 (mean grade of Tc-99(m)-tetrofosmin=0.79+/-0.65 and of Tl-201=0.95+/-0.65; P less than or equal to 0.05). The results of the present study indicate that the overall diagnostic utility of Tc-99(m) -tetrofosmin in the identification of individual stenosed vessels is c omparable with Tl-201 in both patients with totally occluded coronary arteries and those with significantly stenosed vessels. The regional d istribution of both tracers was lower in myocardial segments supplied by totally occluded coronary arteries with poor collateral flow.