ADENOSINE TL-201 IS SUPERIOR TO EXERCISE TL-201 FOR DETECTING CORONARY-ARTERY DISEASE IN PATIENTS WITH LEFT-BUNDLE-BRANCH BLOCK

Objectives. We sought to assess the comparative diagnostic accuracy of adenosine versus exercise in conjunction with thallium-201 scintigraphy for the detection and localization of coronary artery disease in patients with left bundle branch block on the rest electrocardiogram (ECG). Background. Patients with left bundle branch block on the rest ECG frequently have artifactual reversible septal perfusion defects on exercise thallium-201 scintigraphy. Adenosine thallium scintigraphy is a theoretically attractive alternative in these patients. Methods. One hundred seventy-three consecutive patients with left bundle branch block were evaluated with either exercise thallium (n = 56) or adenosine thallium (n = 117) scintigraphy. The tomographic thallium images were interpreted visually with adjunctive quantitative analysis. Follow-up cardiac catheterization was performed in 31 of the 56 patients in the exercise thallium group and 42 of the 117 patients in the adenosine thallium group. Results. Minor subjective side effects were noted in most patients in the adenosine thallium group (86%); atrioventricular block occurred in seven patients (6%). The overall predictive accuracy was 93% in the adenosine thallium group and 68% in the exercise thallium group (p = 0.01). The combined specificity for the detection of disease in the coronary arteries subtending the septum (the left anterior descending and right coronary arteries) was only 42% with exercise thallium scintigraphy versus 82% with adenosine thallium scintigraphy (p < 0.0002). Conclusions. Adenosine thallium imaging 1) was superior to exercise thallium imaging in the detection of coronary artery disease in patients with left bundle branch block; 2) obviated septal artifacts, thereby markedly improving the specificity in the left anterior descending and right coronary arteries; and 3) was safe in patients with left bundle branch block.