False-positive TI-201 SPECT Studies in Patients with Left Bundle Branch Block Frequency and Clinical Significance

This study reports on the frequency and clinical significance of false-positive thallium studies in the interventricular septum in patients with left bundle branch block. In a 3-year period, 93 studies were performed on patients with complete left bundle branch block and sinus rhythm. Of these, 29 had a reversible septal defect; 17 are scored false-positive although only six had angiographic proof of normal left anterior descending coronary arteries. We conclude that thallium scintigraphy is indicated in patients with left bundle branch block, but caution is justified when reversible ischemia is demonstrated scinti-graphically.