LEFT-VENTRICULAR EJECTION FRACTION ASSESSED FROM GATED TECHNETIUM-99M-SESTAMIBI SPECT

By means of ECG gating of tomographic (SPECT) Tc-99m-sestamibi (MIBI) images, myocardial perfusion and wall thickening have been evaluated a fter a single tracer injection. To determine if left ventricular eject ion fraction (LVEF) can also be measured from gated MIBI SPECT, 30 pat ients 1 wk to 6 mo after myocardial infarction (MI) received 22-30 mCi Tc-99m-MIBI during treadmill exercise. Eight frame per cardiac cycle gated MIBI 180-degrees SPECT was performed 60 min thereafter. Using 6. 4-mm thick mid-ventricular vertical and horizontal long-axis slices fr om R-wave triggered end-diastolic and end-systolic frames, two indepen dent observers manually drew endocardial borders at a count level of 3 4% of the maximum. LVEF was computed by the Simpson's rule method, cor rected for the average point spread function of the SPECT camera. Resu lts were correlated with LVEF determined from planar gated Tc-99m-bloo d-pool studies performed within 4 days. LVEFs calculated from gated MI BI SPECT ranged from 0.21 to 0.73 and corrElated linearly with gated b lood-pool values (correlation coefficients ranged from 0.79 to 0.88; i nterobserver variability r = 0 75; intraobserver reproducibility r = 0 .75). We conclude that in patients with MI resting LVEF can be determi ned from gated MIBI SPECT, thereby considerably augmenting the techniq ue's diagnostic and prognostic value.