IJCS | Volume 32, Nº5, September/October 2019

544 Figure 2 - GATED SPECT images demonstrating the normal perfusion pattern (upper left), abnormal septal contraction under stress (upper right) and abnormal synchrony after stress with deleted contraction of the septal wall (bottom). Gazzilli et al. Stress-induced left bundle branch block Int J Cardiovasc Sci. 2019;32(5):540-545 Case Report using Lister Software from the Alcyone Miscellaneous Tools (GE Healthcare). Perfusion, regional wall motion scores and synchrony were analyzed by a commercially available software (Corridor 4DM, Invia, Ann Arbor, Michigan) using a 17-segment model. Analysis of stress and rest images did not demonstrate any perfusion defect (figure 2), confirming the results of the previous single-photon emission computed tomography (SPECT); gated images revealed normal ejection fraction and volumes and an abnormal thickening and abnormal motion of the septal wall only in post-stress images. Post-stress dyssynchrony was detected as demonstrated by the delayed septal motion in the phase analysis. Rest images obtained without the presence of LBBB in the ECG showed a normal synchrony of the left ventricle walls. Discussion We reported a case of a patient with EI-LBBB and post-stress dyssynchrony but with normal perfusion. It is known that interpretation of myocardial perfusion SPECT images in patients with persistent LBBB has decreased specificity because of the presence of fixed or reversible perfusion defects in the septal or anteroseptal regions, even with normal blood flow through the LAD artery. 5 In previous studies, septal or anteroseptal perfusion defects were estimated to be observed in approximately 75% of patients with LBBB, although significant LAD stenosis was detected only in 39%. 6 However, in this case the LBBB was transient because it was exercise-induced with spontaneous recovery at rest; this electrocardiographic abnormality was associated with mechanical dyssynchrony, as demonstrated by gated-SPECT andwas associatedwith normal perfusion. According to the literature and our experience, defects in myocardial perfusion SPECT are frequent in patients with persistent LBBB but are not commonly found in patients with EI-LBBB, in which normal myocardial perfusion is often found. 7 Myocardial perfusion PET-CT is a technique that can contribute to increase the accuracy of CAD evaluation in patients with LBBB. Recently, Falcão et al., 8 demonstrated that 82Rb-PET relative myocardial perfusion could discriminate between LBBB patients with and without CAD, even when considering the LAD territory alone. Sillanma et al. 9 demonstrated that LBBB should not be considered as a certain indicator of mechanical