Tl-201 and Tc-99m-MIBI gated SPECT in patients with large perfusion defects and left ventricular dysfunction: Comparison with equilibrium radionuclide angiography

Left ventricular ejection fraction (LVEF) is a major prognostic factor in c oronary artery disease and may be computed by Tc-99m-methoxyisobutyl isonit rile (MIBI) gated SPECT However, (TI)-T-201 remains widely used for assessi ng myocardial perfusion and viability. Therefore, we evaluated the feasibil ity and accuracy of both Tc-99m-MIBI and (TI)-T-201 gated SPECT in assessin g LVEF in patients with myocardial infarction, large perfusion defects and left ventricular (LV) dysfunction. Methods: Fifty consecutive patients (43 men, 7 women; mean age 61 +/- 17y)with a history of myocardial infarction ( anterior, 26; inferior, 18; lateral, 6) were studied. All patients underwen t equilibrium radionuclide angiography (ERNA) and rest myocardial gated SPE CT, either 1 h after the injection of 1110 MBq (TC)-T-99m-MIBI (n = 19, gro up 1) or 4 h after the injection of 185-203 MBq (TI)-T-201 (n = 31, group 2 ) using a 90 degrees dual-head camera. After filtered backprojection (Butte rworth filter: order 5, cutoff 0.25 Tc-99m or 0.20 (TI)-T-201), LVEF was ca lculated from reconstructed gated SPECT with a previously validated semiaut omatic commercially available software quantitative gated SPECT (QGS). Perf usion defects were expressed as a percentage of the whole myocardium planim etered by bull's-eye polar map of composite nongated SPECT. Results: Gated SPECT image quality was considered suitable for LVEF measurement in all pat ients. Mean perfusion defects were 36% +/- 18% (group 1), 33% +/- 17% (grou p 2), 34% +/- 17% (group 1 + group 2). LVEF was underestimated using gated SPECT compared with ERNA (34% +/- 12% and 39% +/- 12%, respectively; P = 0. 0001). Correlations were high (group 1, r = 0.88; group 2, r = 0.76; group 1 + group 2, r = 0.82), and Bland-Altman plots showed a fair agreement betw een gated SPECT and ERNA. The difference between the two methods did not va ry as LVEF, perfusion defect size or severity increased or when the mitral valve plane was involved in the defect. Conclusion: LVEF measurement is fea sible using myocardial gated SPECT with the QGS method in patients with lar ge perfusion defects and LV dysfunction. However, both (TI)-T-201 and Tc-99 m-MIBI gated SPECT similarly and significantly underestimated LVEF in patie nts with LV dysfunction and large perfusion defects.