Usefulness of gated SPECT myocardial imaging in evaluation of patients with inferior myocardial infarction.

OBJECTIVE

Gated single photon emission computed tomography (gated SPECT) myocardial imaging gives useful information about the extent and severity of perfusion abnormalities (PA) and global left ventricular (LV) function in patients with coronary artery disease. The aim of this study was to evaluate by gated SPECT myocardial imaging differences in perfusion scores and LV function between stress and rest in patients with mild left ventricular dysfunction and/or normal function and previous inferior myocardial infarction (IMI) and to detect myocardial stunning.

MATERIALS AND METHODS

The study included 77 patients (age 53 ± 8.21) with mild left ventricular dysfunction and previous IMI divided into two groups. Group 1 consisted of 34 patients with IMI and additional ischemia on perfusion scan and group 2 with 43 patients with previous IMI without ischemia on perfusion scan. All patients underwent a 2-day stress-rest gated SPECT myocardial imaging protocol with 99m technetium-methoxyisobutylisonitrile ((99m)Tc-MIBI).

RESULTS

There was a more significant post-stress to rest decrease in ejection fraction (EFps) in patients with IMI and additional ischemia (group 1) than in patients with IMI (group 2) (-1.5 ± 2.5 vs. 1.5 ± 2.3, p < 0.001). In group 1, there was a significant increase in post-stress end-systolic volume (ESVps) in comparison to ESVr (70.4 ± 29.8 vs. 66.2 ± 26.2 ml, p = 0.044). However, the decrease in EF post-stress to rest did not reach the level of significance (51.7 ± 10.8 vs. 53.2 ± 10.2%, p = 0.147). The extent and severity of perfusion abnormalities were higher on stress (SSS) than on rest images (SRS) (13.9 ± 8.6 vs. 8.3 ± 7.8, p < 0.001). There was no difference in global LV parameters or perfusion abnormalities in patients in group 2 between stress and rest except for a significant increase in the post-stress EF to rest value (57.9 ± 11.9 vs. 56.2 ± 10.5%, p = 0.018). Severe decrease of post-stress EF to rest was found in 12 (16%) patients indicating stunning.

CONCLUSION

In patients with mild left ventricular dysfunction and IMI with additional ischemia there is evidence of a decrease in the post-stress EF with an increase in the post-stress ESV. In addition, a significant association between the decrease of post-stress EF with the extent and severity of perfusion abnormalities was detected. Gated SPECT myocardial imaging has an important role in the evaluation of perfusion and LV function in patients with IMI especially in patients with additional ischemia.