Comparison of technetium 99m-tetrofosmin and thallium-201 single photon emission computed tomographic imaging for the assessment of viable myocardium in patients with left ventricular dysfunction

Background. Tetrofosmin is a new technetium 99m-labeled myocardial perfusion agent that has demonstrated favorable imaging characteristics in recent clinical trials, However, it is not certain whether Tc-99m-tetrofosmin compared with thallium 201 would underestimate myocardial viability in regions with left ventricular dysfunction. Methods. To this end 15 patients (mean age 52 +/- 7 years) with coronary artery disease and left ventricular dysfunction (ejection fraction 35% +/- 8%) documented on angiography underwent both quantitative rest-redistribution Tl-201 and rest Tc-99m-tetrofosmin single photon emission computed tomography imaging. Results. Of 240 total segments on rest-redistribution Tl-201 protocol 139 (58%) segments had irreversible Tl-201 defects, Of these segments 79 (57%) had only mild to moderate reduction of Tl-201 uptake (51% to 85% of normal uptake), whereas the remaining 60 (43%) had severely reduced tracer uptake (less than or equal to 50% of normal uptake), On Tc-99m-tetrofosmin protocol 180 (75%) segments had abnormal Tc-99m-tetrofosmin uptake; of these segments 120 (67%) had mild to moderate reduction of Tc-99m-tetrofosmin uptake, whereas 60 (33%) had severely reduced activity. Among hypokinetic regions concordance between Tl-201 and Tc-99m-tetrofosmin regarding myocardial viability with a cutoff point of 50% of peak activity was obtained in 28 (90%) of 31 segments (K' = 0.80), leaving only 3 of 31 regions discordant (p = NS), Similarly, among akinetic or dyskinetic regions concordance between the two tracers regarding myocardial viability was achieved in 54 (93%) regions (K' = 0.75), leaving only 4 of the 58 regions discordant (p = NS). Conclusions. These data show that when the severity of uptake was considered within abnormal segments, a similar amount of Tl-201 viable regions were observed by Tc-99m-tetrofosmin Thus these two agents may provide comparable information about myocardial viability when quantitative analysis of defect severity is performed.