FAST TECHNETIUM 99M-LABELED SESTAMIBI GATED SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY FOR EVALUATION OF MYOCARDIAL-FUNCTION

Background. This study assesses the feasibility of Tc-99m-labeled sest amibi electrocardiographic gated single-photon emission computed tomog raphy (SPECT) with a short acquisition time (6.7 minutes, ''fast'' gat ed SPECT) for the evaluation of stress myocardial perfusion and postst ress myocardial function. Simultaneous assessment of stress perfusion and poststress function is possible with standard gated SPECT acquisit ion (19.3 minutes) of stress-injected sestamibi. Sestamibi gated SPECT can be used to evaluate regional wall motion (PWM), thickening, and l eft ventricular ejection fraction (LVEF); the feasibility of fast gate d SPECT has not been evaluated previously. Methods and Results. Fifty patients were studied who underwent treadmill exercise, sestamibi inje ction (25 to 30 mCi), and standard gated SPECT 15 minutes after exerci se, immediately followed by fast gated SPECT. All patients underwent r est (TI)-T-201 SPECT before exercise testing. All studies were analyze d by semiquantitative visual scoring. Both standard and fast gated SPE CT were read for stress perfusion and poststress wall motion and thick ening, dividing the left ventricle into 20 segments, on a 5-point scal e described previously. The measurement of LVEF used a previously desc ribed automatic algorithm. Average myocardial counts per pixel were 58 +/- 19 for standard gated SPECT and 13 +/- 4 for fast gated SPECT (p = 0.0001). Heart/lung ratio was 10.2 +/- 4.8 for regular gated SPECT a nd 10.3 +/- 5.7 for fast gated SPECT (difference not significant). Per fusion analysis showed exact agreement in 92% of the segments (kappa = 0.76; p < 0.01). Correlation between LVEFs measured from standard and fast gated SPECT was 0.94. Analysis of 998 segments (two segments wer e uninterpretable) showed exact agreement in 96% (kappa = 0.89; p < 0. 001) for RWM and 94% (kappa = 0.83; p < 0.001) for thickening between standard and fast gated SPECT. In 225 segments with abnormal RWM and 1 89 segments with abnormal thickening by both standard and fast gated S PECT, exact agreements were 0.92 for RWM (kappa = 0.90; p < 0.001) and 0.87 for thickening (kappa = 0.80; p < 0.01). Conclusions. Our data d emonstrate that fast sestamibi gated SPECT is feasible and yields resu lts equivalent to those of standard sestamibi gated SPECT with respect to left ventricular regional and global function.