Thallium-201 exercise scintigraphy and left bundle branch block

Abstract

Results from several centers have shown that the sensitivity and specificity of exercise thallium-201 (Tl-201) myocardial imaging for detecting myocardial ischemia are superior to those of conventional exercise electrocardiography. 1–6 However, the value of Tl-201 myocardial imaging depends on patient selection, acquisition technique and mode (quantitative interpretation) of images. In patients with normal intraventricular conduction, sensitivity and specificity of Tl-201 exercise myocardial imaging has been reported as 85 to 90%, compared with 65 to 70% for exercise electrocardiography alone. 7 Limited information is available about the value of Tl-201 myocardial imaging in patients with left bundle branch block (LBBB). McGowan et al 8 examined 27 patients with LBBB using potassium-43 or rubidium-81 to exclude coronary artery disease (CAD). Hirzel et al 9 examined 19 patients by Tl-201 scintigraphy and coronary angiography for the same purpose. Both studies found a decreased septal uptake of the radionuclide, suggesting a narrowed left anterior descending coronary artery. However, most patients who had a septal defect had a normal left anterior descending coronary artery by coronary angiography. To further assess the value of Tl-201 myocardial imaging in patients with LBBB and chest pain and to study its relation to CAD, the present study was undertaken in 24 patients with LBBB admitted to the hospital because of chest pain.