Clinical validation of technetium‐99m MIBI‐gated single‐photon emission computed tomography (SPECT) for avoiding false positive results in patients with left bundle‐branch block: Comparison with stress‐rest nongated SPECT

BACKGROUND: Septal perfusion defects are common on myocardial perfusion single-photon emission computed tomography (SPECT) slices in patients with left bundle-branch block (LBBB) in the absence of coronary artery disease. HYPOTHESIS: The use of gated myocardial perfusion SPECT imaging in such patients should be clinically validated. The aims of this study were, therefore, to validate clinically the use of gated myocardial SPECT imaging to avoid false positive septal perfusion defects in patients with LBBB and to compare nongated and gated SPECT imaging techniques in the same patients in the same imaging session. METHODS: We performed stress-rest myocardial perfusion SPECT and resting gated SPECT using Technetium-99m MIBI in 25 patients with LBBB and in 6 control subjects. Stress-rest SPECT images and end-diastolic and end-systolic gated SPECT slices were assessed visually and quantitatively (septum/lateral wall count ratio). Coronary angiography was performed in 15 patients with LBBB and in all 6 control subjects. RESULTS: Stress-rest (nongated) SPECT slices and end-diastolic and end-systolic gated SPECT images were normal in all control subjects. Stress-rest (nongated) SPECT imaging revealed septal perfusion defect in 20 (11 reversible, 9 irreversible) patients with LBBB, whereas the figures were 15 and 5 for end-systolic and end-diastolic gated SPECT images, respectively. Coronary angiography results were normal in all control subjects and in 15 patients with LBBB. Quantitative analysis of gated SPECT images revealed no statistically significant difference between patients with LBBB and control subjects in end-diastolic mean septum/lateral wall count values (0.86 +/- 0.19 in LBBB vs. 0.98 +/- 0.15 in normal subjects, p > 0.05), but the difference was statistically significant for end-systolic, stress, and rest values (p < 0.001 for all). CONCLUSION: Gated SPECT imaging, particularly end-diastolic images, revealed fewer false positive results and thus can be used to avoid false positive septal perfusion defects commonly seen in stress-rest (nongated) myocardial perfusion SPECT in patients with LBBB.