DETECTION OF LEFT ANTERIOR DESCENDING CORONARY-ARTERY DISEASE IN PATIENTS WITH LEFT-BUNDLE-BRANCH BLOCK

The detection of coronary artery disease is difficult if a patient has electrocardiographic evidence of left bundle branch block (BBB). Septal blood flow may be reduced in patients with left BBB, despite no angiographic evidence of left anterior descending (LAD) coronary artery disease. We have developed a new method of quantification of Thallium-201 single-photon emission computed tomographic (SPECT) images with the aim of better separating patients with left BBB and LAD disease from those with left BBB alone. The study cohort comprised 8 normal subjects (group I) and 20 patients with left BBB and chest pain who underwent thallium-201 SPECT imaging and coronary angiography. Eight patients (group II) had less-than-or-equal-to 50% LAD stenosis, and 12 (group III) had greater-than-or-equal-to 70% LAD stenosis. Septal abnormality scores on the second short-axis slice from the base were computed, based on comparison of each subject's short-axis circumferential profile with a normal reference curve. This followed a procedure in which each profile was scaled to minimize differences in its absolute level in relation to the reference curve. Septal abnormality scores on stress images were 0.8 +/- 22 for group I, 27 +/- 43 for group II, and 165 +/- 67 for group III (p = 0.15 for group I vs II, and p <0.0001 between groups I and III, and II and III). On delayed images, septal abnormality scores were 0.9 +/- 25, 3.2 +/- 31, and 101 +/- 51 in groups I, II and III, respectively (p = not significant for group I vs II, and p <0.0001 for group I vs III, and II vs III). This new method of analyzing stress thallium-201 SPECT circumferential profiles separated patients with left BBB and significant LAD disease, both with and without previous anteroseptal myocardial infarction, from those with left BBB alone.