Diagnosis of coronary artery disease with tl-201 SPECT in patients with left bundle branch block: Importance of alternative interpretation approachesfor left anterior descending coronary lesions

Left bundle branch block (LBBB) is a strong predictor of mortality in the p resence of coronary artery disease (CAD). Noninvasive evaluation of CAD in these patients has some difficulties. Exercise-induced electrocardiographic ST segment changes are nondiagnostic, and several scintigraphic studies ha ve reported false-positive anteroseptal and septal perfusion defects up to 80%. The authors aimed to assess the diagnostic accuracy of thallium-201 (T I-201) exercise myocardial single photon emission computerized tomography ( SPECT) in comparison with coronary angiography (CAG) for detection of CAD i n patients with LBBB. Seventy-seven consecutive patients suffering from che st pain with complete and permanent LBBB were included in the study. All pa tients (40 women, 37 men. mean age = 54 +/-7 years) were studied with TI-20 1 exercise SPECT and coronary angiography. TI-201 exercise SPECT for diagno sis of left anterior descending (LAD) artery lesions was interpreted by usi ng three different approaches: method A (conventional approach), method B ( involvement of anterior and septal wall regardless of apical wall), and met hod C (apical approach: involvement of anterior septal and apical wail). Me thods A and B gave a sensitivity of 100% each but a specificity of 47% and 56%, respectively. Although method C gave a higher value of specificity tha n that of methods A and B (98% vs 47% and 56%, respectively p < 0.05), the sensitivity of method C significantly decreased in respect to methods A and B (33% vs 100% p<0.01). Isolated septal defects were evaluated separately. Isolated septa defects on exercise TI-201 SPECT were detected in 11 patien ts, and none of them had CAD according to CAG results. Isolated septal wall involvement had a sensitivity of 0% and a specificity of 74%. The sensitiv ity and specificity of TI-201 SPECT for diagnosis of CAD in the right coron ary and left circumflex artery territories were 91% and 89%, respectively. In conclusion, the apical approach increased the specificity and decreased the sensitivity of the test. Isolated septal defects seem to have no value for diagnosis of CAD in patients with left bundle branch block.