Letter: Hyperglycericacidaemia with hyperglycinaemia: a new inborn error of metabolism.

Abstract

Left ventricular ejection fraction (LVEF) is a major prognostic factor in coronary artery disease and may be computed by ^99mTc-methoxyisobutyl isonitrile (MIBI) gated SPECT. However, ²⁰¹Tl remains widely used for assessing myocardial perfusion and viability. Therefore, we evaluated the feasibility and accuracy of both ^99mTc-MIBI and ²⁰¹Tl gated SPECT in assessing LVEF in patients with myocardial infarction, large perfusion defects and left ventricular (LV) dysfunction. <b>Methods:</b> Fifty consecutive patients (43 men, 7 women; mean age 61 ± 17 y) with a history of myocardial infarction (anterior, 26; inferior, 18; lateral, 6) were studied. All patients underwent equilibrium radionuclide angiography (ERNA) and rest myocardial gated SPECT, either 1 h after the injection of 1110 MBq ^99mTc-MIBI (n = 19, group 1) or 4 h after the injection of 185–203 MBq ²⁰¹Tl (n = 31, group 2) using a 90° dual-head camera. After filtered backprojection (Butterworth filter: order 5, cutoff 0.25 ^99mTc or 0.20 ²⁰¹Tl), LVEF was calculated from reconstructed gated SPECT with a previously validated semiautomatic commercially available software quantitative gated SPECT (QGS). Perfusion defects were expressed as a percentage of the whole myocardium planimetered by bull9s-eye polar map of composite nongated SPECT. <b>Results:</b> Gated SPECT image quality was considered suitable for LVEF measurement in all patients. Mean perfusion defects were 36% ± 18% (group 1), 33% ± 17% (group 2), 34% ± 17% (group 1 + group 2). LVEF was underestimated using gated SPECT compared with ERNA (34% ± 12% and 39% ± 12%, respectively; <i>P</i> = 0.0001). Correlations were high (group 1, <i>r</i> = 0.88; group 2, <i>r</i> = 0.76; group 1 + group 2, <i>r</i> = 0.82), and Bland-Altman plots showed a fair agreement between gated SPECT and ERNA. The difference between the two methods did not vary as LVEF, perfusion defect size or severity increased or when the mitral valve plane was involved in the defect. <b>Conclusion:</b> LVEF measurement is feasible using myocardial gated SPECT with the QGS method in patients with large perfusion defects and LV dysfunction. However, both ²⁰¹Tl and ^99mTc-MIBI gated SPECT similarly and significantly underestimated LVEF in patients with LV dysfunction and large perfusion defects.