[Evaluation of complete left bundle branch block with normal coronary artery using positron emission CT (PET) and...

False-positive Tl-201 scintigraphy in patients with complete left bundle-branch block (CLBBB) and normal coronary artery had been reported by several authors. However the reason for this phenomenon remained to be clarified. We investigated 2 patients (case 1; a 65-year-old male, case 2; a 58-year-old male) with CLBBB using positron emission computed tomography (PET). Coronary angiography revealed normal coronary artery in both cases. In both cases, Tl-201 stress scintigraphy demonstrated definite perfusion defect at the anteroseptal region without redistribution, although PET study using F-18 fluorodeoxyglucose (18F-FDG) revealed defect at the septal wall. This indicates that perfusion defect detected by Tl-201 scintigraphy relates rather not to ischemic myocardium with a viable region, but to necrotic or fibrous tissue. Thus, PET is a useful tool in investigating viability of abnormal myocardium when other study has failed to do so. Our cases with CLBBB suggested that there was abnormal flow and metabolism at the anteroseptal region, possibly relating to the pathogenesis of CLBBB.