Stress-Redistribution-Reinjection and Rest-Redistribution Thallium Imaging for Assessing Viable Myocardium Comparison With Metabolic Activity by Positron Emission Tomography

Background. Stress thallium scintigraphy provides important diagnostic and prognostic information in patients with coronary artery disease by demonstrating regional myocardial ischemia. However, if the clinical question being addressed is whether a region is viable and not whether there is inducible ischemia, then it may be more reasonable to perform rest-redistribution imaging rather than stress-redistribution imaging followed by either reinjection or late redistribution. Therefore, we determined whether stressredistribution-reiijection and rest-redistribution imaging provide the same information regarding myocardial viability. Methods and Results. Both stress-redistribution-reinijection and rest-redistribution thallium single photon emission computed tomographic imaging was performed in 41 patients with chronic stable coronary artery disease, with quantitative analysis of regional thallium activity. Thallium reinjection was performed immediately after the 3to 4-hour redistribution Images were completed. Ofthe 155 myocardial regions with perfusion defects on the stress images, 91 (59%) were irreversible on conventional 3to 4-hour redistribution images. When the outcomes of these irreversible regions were assessed after reinjection and compared with rest-redistribution images, there was concordance ofdata regarding myocardial viability (normal/reversible or irreversible) in 72 of the 91 (79%) irreversible defects. Twenty of the 41 patients also underwent positron emission tomography at rest with [18Flfluorodeoxyglucose and [11Owater. In these patients, stressredistribution-reinjection and rest-redistribution imaging provided concordant information regarding myocardial viability in 427 (72%) of594 myocardial regions and discordance in 167 regions. However, when irreversible thallium defects were further analyzed according to the severity of the thallium defect in these discordant regions, 149 of 167 (89%1) demonstrated only mild-to-moderate reduction in thallium activity (51% to 85% of normal activity), and positron emission tomography verified 98% of these regions to be metabolically active and viable. Thus, when the severity of thallium activity was considered within irreversible thallium defects, the concordance between stress-redistribution-reinjection and rest-redistribution imaging regarding myocardial viability increased to 94%. Conclusions. These data indicate that one oftwo imaging modalities, either stress-redistribution-rei'jection or rest-redistribution imaging, may be used for identifying viable myocardium. However, if there are no contraindications to stress testing, stress-redistribution-rewinection imaging provides a more comprehensive assessment of the extent and severity of coronary artery disease by demonstrating regional myocardial ischemia without jeopardizing information on myocardial viability. (Cirultion. 1993;88:941-952.) KEY WORDs * coronary artery disease * myocardium * ischemia * scintigraphy * tomography