REST-INJECTED TL-201 REDISTRIBUTION AND RESTING TC-99M METHOXYISOBUTYLISONITRILE UPTAKE IN CORONARY-ARTERY DISEASE - RELATION TO THE SEVERITY OF CORONARY-ARTERY STENOSIS

To compare rest-injected thallium-201 (TI) redistribution and resting technetium-99m methoxyisobutylisonitrile (Tc-99m-MIBI) myocardial uptake in chronic coronary artery disease (CAD), 15 patients with angiographically proven CAD and left ventricular (LV) dysfunction (ejection fraction 34% +/- 9%) were studied. All patients underwent rest-redistribution Tl and resting Tc-99m-MIBI cardiac imaging. Gated Tc-99m-MIBI images were also acquired to assess regional LV wall motion (WM). Myocardial segments (n=225) were divided into three groups on the basis of the degree of coronary artery stenosis: group 1 (total occlusion, n=82), group 2 (50%-99% of stenosis, n=84) and group 3 (<50% of stenosis, n=59). WM was significantly worse in groups 1 and 2 compared to group 3 (P<0.001), but no difference was observed between groups 1 and 2. TI and Tc-99m-MIBI uptake were significantly lower in groups 1 and 2 compared to group 3 (P<0.001), and in group 1 compared to group 2 (P<0.001). When Tl and Tc-99m-MIBI uptake were directly compared, Tl uptake was higher than Tc-99m-MIBI uptake in group 1 (P<0.001), while no significant difference was observed in groups 2 and 3. Thus, both rest-injected Tl redistribution and resting Tc-99m-MIBI uptake reflected the severity of coronary artery stenosis in CAD. However, in myocardial segments with total coronary occlusion Tl uptake was significantly higher than Tc-99m-MIBI uptake. Our data suggest that rest-injected TI redistribution cardiac imaging may identify, more accurately than resting Tc-99m-MIBI imaging, the presence of viable myocardium in chronic CAD, particularly when the coronary blood flow is severely impaired.