Left ventricular ejection fraction assessed from gated technetium-99m-sestamibi SPECT.

Abstract

By means of ECG gating of tomographic (SPECT) 99mTc-sestamibi (MIBI) images, myocardial perfusion and wall thickening have been evaluated after a single tracer injection. To determine if left ventricular ejection fraction (LVEF) can also be measured from gated MIBI SPECT, 30 patients 1 wk to 6 mo after myocardial infarction (MI) received 22-30 mCi 99mTc-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 from R-wave triggered end-diastolic and end-systolic frames, two independent observers manually drew endocardial borders at a count level of 34% of the maximum. LVEF was computed by the Simpson's rule method, corrected for the average point spread function of the SPECT camera. Results were correlated with LVEF determined from planar gated 99mTc-blood-pool studies performed within 4 days. LVEFs calculated from gated MIBI SPECT ranged from 0.21 to 0.73 and correlated linearly with gated blood-pool values (correlation coefficients ranged from 0.79 to 0.88; interobserver variability r = 0.75; intraobserver reproducibility r = 0.75). We conclude that in patients with MI resting LVEF can be determined from gated MIBI SPECT, thereby considerably augmenting the technique's diagnostic and prognostic value.

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