Assessment of myocardial viability by quantitative analysis of stress Tl-SPECT

Stress Tl-201 tomography (SPECT) is widely used for evaluating myocardial viability. To assess its value, redistribution (RD) on SPECT was compared with metabolic imaging using FDG. Thirty patients with coronary artery disease underwent stress-3 hour Tl-201 SPECT and PET using N-13 ammonia and FDG. RD was classified into 4 grading, including complete RD (CR), incomplete RD (IR), persistent defect (PD) and additional minimal RD (MR) defined as no definite RD on visual analysis but faint RD with Bull's eye quantitative analysis (QNT). All but one segment with CR or IR were viable regions (normal or ischemic regions) by PET. Of 74 segments without RD on visual analysis, 31 segments (42%) had RD by QNT (MR). All of them were viable regions by PET. Thus, QNT identified 31 segments (63%) of the metabolically viable segments which the visual Tl-201 analysis did not show RD and classified as myocardial scar. However, even such QNT cannot detect ischemic myocardium in 18 segments (42%) containing metabolic activity on PET. These data indicate that QNT of RD on Tl-201 SPECT is considered as a valuable means for assessing myocardial ischemia. (author)