Objectives. We prospectively compared myocardial uptake of thallium-201 (201Tl) at rest with rest technetium-99m (99mTc) sestamibi uptake in the same patients, using quantitative single-photon emission computed tomography (SPECT).
Background. Because of only slightly delayed redistribution, 99mTc-sestamibi uptake at rest may be less than 201Tl uptake, thereby underestimating the extent of viability.
Methods. Twenty patients (2.25 stenoses per patient) with a mean left ventricular ejection fraction of 33 ± 2% underwent early and 3-h delayed rest 201Tl SPECT, rest 99mTc-sestamibi SPECT and two-dimensional echocardiography.
Results. The 280 scan segments were classified as either a normal, mild reduction in viability, defined as delayed 201Tl uptake ≤75% and ≥5%, or a severe reduction in viability, defined as delayed 201Tl uptake <50%. Mild and severe defects were further classified as fixed or having rest 201Tl redistribution. Comparisons by patients were made using repeated measures analysis of variance and Dunnett's multiple comparisons test to compare 99mTc-sestamibi with initial rest 201Tl and delayed 201Tl uptake. Twenty patients had at least one mild fixed defect (95 total segments). The average percent uptake in these defects for initial 201Tl, delayed 201Tl and 99mTc-sestamibi was 62.5 ± 2.7%, 63.1 ± 7.1% and 67.3 ± 9.7%, respectively (p = NS). Twelve patients (27 segments) had mild redistribution defects on serial rest 201Tl imaging. The average percent uptake was 61.6 ± 5.2% for initial 201Tl, 67.0 ± 9.1% for delayed 201Tl and 67.7 ± 12.4% for 99mTc-sestamibi defects. Technetium-99m sestamibi uptake was not significantly different than that for delayed 201Tl but was significantly greater than initial 201Tl uptake. Seventeen patients (52 segments) had severe fixed 201Tl defects. The average percent uptake was 38.9 ± 7.3% for initial 201Tl, 38.3 ± 12.2% for delayed 201Tl and 42.7 ± 14.2% for 99mTc-sestamibi defects in these patients (p = NS). Ten patients (19 segments) had severe redistribution defects on rest 201Tl imaging. The average percent uptake was 37.0 ± 8.5% for initial 201Tl, 42.9 ± 8.6% for delayed 201Tl and 44.5 ± 11.3% for 99mTc-sestamibi defects. As was seen for mild 201Tl redistribution defects, 99mTc-sestamibi uptake was significantly higher than initial 201Tl uptake, but not significantly different than delayed 201Tl uptake in these severe defects.
Conclusions. Technetium-99m sestamibi uptake after injection at rest is comparable to 201Tl uptake after injection at rest in patients with severe coronary artery disease and left ventricular dysfunction, suggesting comparable worth for viability assessment.
