EXERCISE TL-201 IMAGING CHARACTERISTICS AND PROGNOSTIC VALUE IN PATIENTS WITH LEFT-BUNDLE-BRANCH BLOCK

To determine the utility of exercise thallium-201 testing in patients with left bundle branch block (LBBB), we studied 61 consecutive patien ts referred to our laboratory from 1986 to 1989. We divided the patien ts into two groups for further analysis. Those with known coronary art ery disease (CAD), documented either by cardiac catheterization or pre vious myocardial infarction, formed group I. Patients with no evidence of CAD formed grup II. Thirty-three of the 28 patients in group I had an abnormal thallium scan (87%) versus 7 of the 23 in group II (< 0.0 01). Although the number and location of the perfusion defects was sim ilar in the patients with abnormal scans in either group, the proporti on of severe defects was significantly higher in the patients in group I (21 vs. 5%) (p < 0.05), as well as the proportion of patients with increased thallium lung uptake (63 vs. 13%) (p < 0.001) and left ventr icular (LV) cavity dilation (69 vs. 9%) (p < 0.001). We conclude that thallium exercise testing is useful evaluating patients with LBBB. Pat ients with 'isolated' LBBB have a low incidence of thallium perfusion abnormalities when compared to those with known CAD. The relative abse nce of severe perfusion defects and scan markers of exercise-induced L V dysfunction in this group correlated with a good clinical outcome.