Lung Uptake of 99mTc-sestamibi during Routine Gated Exercise SPECT Imaging: Comparison with Left Ventricular Ejection Fraction and Severity of Perfusion Defect

Jeong, Shin Young; Lee, Jaetae; Bae, Jin Ho; Ahn, Byeong Cheol; Lee, Kyu Bo

Abstract

BACKGROUND
Lung-to-heart uptake ratio (LHR) in (201) Tl-chloride myocardial perfusion scan is believed to be a reliable marker for left ventricular (LV) dysfunction, but the clinical value of LHR is controversial for 99mTc-MIBI imaging. Furthermore, most of results suggesting lung uptake of 99mTc-MIBI as a potential marker for LV dysfunction used immediate post-stress images, instead of routine images acquired 1 hour after tracer injection. The goal of our study was to investigate whether LHR evaluated with routine gated 99mTc-MIBI imaging can reflect the degree of perfusion defect or left ventricular performance. SUBJECTS AND METHODS: 241 patients underwent exercise 99mTc-MIBI myocardial SPECT were classified into normal myocardial perfusion (NP, n=135) and abnormal myocardial perfusion (AP, n=106) group according to the presence of perfusion defect. LHR was calculated from anterior projection image taken at 1-hour after injection. Two regions of interest (ROIs) were placed on left lung above LV and on myocardium showing the highest radioactivity. Subjects were classified by left ventricular ejection fraction (LVEF), as Gr-I: > 50%, Gr-II: 36-50%, Gr-III: < 36% and by summed stress score (SSS), as Gr-A: < 4, Gr-B: 4-8, Gr-C: 9-13, Gr-D: > 13, LHR was compared among these groups. RESULTS: In NP group (n=135), LHR, were higher in men than women (men: 0.311+/-0.03, women: 0.296+/-0.03, p< 0.05). Significant difference, in LHR were found between NP and AP groups both for men and women (men: 0.311+/- 0.03 vs. 0.331+/- 0.06, women: 0.296+/-0.03 vs. 0.321+/-0.07, p< 0.05). There were weak negative correlation between LHR and LVEF (r=-0.342, p< 0.05) and weak positive correlation between LHR and SSS (r=0.478, p< 0.05) in men, but not in women (LVEF: r=-0.279, p=0.100, SSS: r=0.276, p=0.103). Increased LHR was defined when for more than mean + 2SD value (men> or = 0.38, women> or = 0.37) of the LHR of the subject with normal perfusion. Increased LHR were observed more frequently in subjects with lower LVEF (Gr-I: 11.1%, Gr-II: 27.0%, Gr-III: 36.4%, p< 0.05) and higher SSS (Gr-A: 14.0%, Gr-B: 6.7%, Gr-C: 18.2%, Gr-D: 40.7%, p< 0.05). CONCLUSIONS: LHRs obtained from routine 99mTc-MIBI gated SPECT images were weakly correlated with LVEF and perfusion defect. Although significant overlaps were observed between normal and abnormal perfusion group, LHRs could be used as an indirect marker of severe perfusion defect or reduced left ventricular function.