Assessment of myocardial perfusion and viability with technetium-99m methoxyisobutylisonitrile and thallium-201 rest redistribution in chronic coronary artery disease

We compare thallium-201 rest redistribution and fluorine-18 fluorodeoxyglucose (¹⁸F]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^99mTc-MIBI, (2) rest^99mTc-MIBI, (3)²⁰¹T1 rest-redistribution single-photon emission tomography, (4) ¹⁸F]FDG positron emission tomography. The left ventricle was devided into 11 segments on matched tomographic images. The segment with the highest activity at stress was taken as the reference (activity=100%). Perfusion defects at^99mTc-MIBI rest were classified as severe (activity<50%), moderate (activity 50%–60%) or mild (activity 60%–85%). Uptakes of ¹⁸F]FDG and rest-redistributed²⁰¹Tl were recognized as significant if they exceeded 50% of that in the reference segment. Among the 33 segments with severe^99mTc-MIBI rest perfusion defects, 21 had significant ¹⁸F]FDG and 10 significant rest-redistributed²⁰¹Tl uptake. As regards the 37 segments with moderate defects, ¹⁸F]FDG was present in 29 and²⁰¹Tl in 31, while of the 134 segments with mild defects, 128 showed ¹⁸F]FDG uptake, and 131,²⁰¹Tl uptake. In conclusion, there is an inverse relationship between the severity of^99mTc-MIBI perfusion defects and the uptake of rest-redistributed²⁰¹Tl and ¹⁸F]FDG. Both tracers are adequate markers of viability in mild and moderate defects; in severe defects²⁰¹Tl might underestimate the presence of viability as assessed by ¹⁸F]FDG.