This study was designed to investigate the relationship between myocardial perfusion defect in single photon emission tomography(SPECT) and the difference in left ventricular functional parameters obtained after stress and at rest.

Eighty five patients known to have coronary artery disease (CAD) or suspected to have CAD underwent gated Tc-99m sestamibi SPECT using one or separate day rest/stress protocol. We compared post-stress left ventricular ejection fraction (LVEF-s) with that at rest (LVEF-r) in gated myocardial SPECT. We considered myocardial stunning was developed when LVEF was >5% lower than that at rest.

Forty one (48%) patients demonstrated reversible or irreversible perfusion defects in gated perfusion SPECT (group 1). Forty four (52%) patients demonstrated normal perfusion status (group 2). In group 1, LVEF-s was significantly lower than that at rest([mean±SD] 46±15.5 vs 48±16.0 respectively, p<0.05). In group 2, There was no significant difference among LVEF-s and LVEF-r(60±7.6 vs 61±7.9, p=NS). In group 1, no difference was observed between LVEF-s and LVEF-r by stress modes. In 13 (32%) of 41 patients with perfusion defects, LVEF-s was >5% lower than LVEF-r.

The LVEF obtained after stress with gated SPECT may not reflect true resting values. We recommend gated myocardial perfusion SPECT should be performed also at rest especially in patients with myocardial perfusion defects.