Comparison between rest technetium-99m-tetrofosmin and rest-redistributionthallium-201 SPECT in stable patients with healed myocardial infarction

Resting Tc-99m-tetrofosmin (TF) uptake was compared with thallium (Tl-201) rest-redistribution (R-RD) uptake in patients with previous myocardial infa rction (MI) and significant coronary artery disease (CAD) to assess the abi lity of TF to detect viable myocardium. We studied 30 patients (21 males an d nine females, mean age 53.9 +/- 12.5 years) with prior MI and left ventri cular dysfunction who had been referred for coronary revascularization proc edures. Myocardial single photon emission computed tomography (SPECT) image s were obtained 1 h after injection of 750 MBq of TF. Within I week of the TT study, R-RD Tl-201 SPECT imaging was performed after injection of 111 MB q of Tl-201. Quantitative analysis was performed in 21 segments. Viability was defined as the presence of tracer uptake greater than 50% of the peak a ctivity on baseline studies or after reversibility. There was significant c orrelation between the quantitative regional R-RD Tl-201 activity and the r esting TF activity (r=0.88, P<0.001). Quantitative analysis showed that the uptake of the two tracers was comparable in normal segments as well as in segments with fixed Tl-201 defects. In contrast, in segments with reversibl e Tl-201 defects, TF uptake was significantly greater than resting Tl-201 u ptake, but lower than R-RD Tl-201 uptake. There were 52 segments (47% of th e severely reduced segments on TF images) that showed no viability with TF, but were viable on the redistribution Tl-201 studies. We conclude that qua ntitative resting TF SPECT underestimates the presence of viable myocardium compared with R-RD Tl-201 imaging on the basis of using 50% of the peak ac tivity as the viability threshold. ((C) 2001 Lippincott Williams & Wilkins) .