ASSESSMENT OF MYOCARDIAL PERFUSION AND VIABILITY WITH TC-99M METHOXYISOBUTYLISONITRILE AND TL-201 REST REDISTRIBUTION IN CHRONIC CORONARY-ARTERY DISEASE

We compare thallium-201 rest redistribution and fluorine-18 fluorodeoxyglucose ([F-18]FDG) for the assessment of myocardial viability within technetium 99m methoxyisobutylisonitrile (MIBI) perfusion defects in 27 patients with chronic stable coronary artery disease. The following studies were performed: (1) stress Tc-99m-MIBI, (2) rest Tc-99m-MIBI, (3) Tl-201 rest-redistribution single-photon emission tomography, (4) [F-18]FDG positron emission tomography. The left ventricle was devided into II segments on matched tomographic images, The segment with the highest activity at stress was taken as the reference (activity=100%). Perfusion defects at Tc-99m-MIBI rest were classified as severe (activity <50%), moderate (activity 50%-60%) or mild (activity 60%-85%). Uptakes of [F-18]FDG and rest-redistributed Tl-201 were recognized as significant if they exceeded 50% of that in the reference segment. Among the 33 segments with severe Tc-99m-MIBI rest perfusion defects, 21 had significant [F-18]FDG and 10 significant rest-redistributed Tl-201 uptake. As regards the 37 segments with moderate defects, [F-18]FDG was present in 29 and Tl-201 in 31, while of the 134 segments with mild defects, 128 showed [F-18]FDG uptake, and 131, Tl-201 uptake. In conclusion, there is an inverse relationship between the severity of Tc-99m-MIBI perfusion defects and the uptake of rest-redistributed Tl-201 and [F-18]FDG. Both tracers are adequate markers of viability in mild and moderate defects; in severe defects Tl-201 might underestimate the presence of viability as assessed by [F-18]FDG.