SEPTAL PERFUSION AND WALL THICKENING IN PATIENTS WITH LEFT-BUNDLE-BRANCH BLOCK ASSESSED BY TECHNETIUM-99M-SESTAMIBI GATED TOMOGRAPHY

Septal hypoperfusion is often observed in patients with complete left bundle branch block (LEES) in myocardial perfusion imaging. Abnormal w all motion in the septal region may potentially cause artifactual perf usion abnormalities. To assess the effect of abnormal wall thickening on myocardial perfusion images, EGG-gated sestamibi SPECT was performe d on 12 patients with LBBB and 10 normal subjects used as controls. Me thods: After administration of 740 MBq Tc-99m-sestamibi injection at r est, EGG-gated SPECT was obtained 60 min later with division of the ca rdiac cycle into eight frames. Results: Septal hypoperfusion was noted in 10 patients on nongated images and 11 patients on end-systolic (ES ) images, whereas only two patients showed abnormalities on end-diasto lic (ED) images. The septal to lateral wall count ratio in the LBBB gr oup was lower(0.72 +/- 0.09) than in the control group (0.84 +/- 0.09) (p < 0.01) at nongated images, while it was similar at ED images (0.8 4 +/- 0.11 versus 0.86 +/- 0.12; ns). In addition, the count increase from ED to ES during a cardiac cycle in the septal region was smaller compared with the lateral region in the LEED patients (25% +/- 19% in the septal region, versus 48% +/- 14% in the lateral region; p < 0.01) , indicating less wall thickening in the septal region. Conclusion: Sm aller count increase due to reduced wall thickening in the septal regi on may mimic hypoperfusion in patients with LEED. This artifact can be eliminated with EGG-gated Tc-99m-sestamibi SPECT, particularly with E D images.