Diagnostic and prognostic value of gated myocardial perfusion single-photon emission computed tomography in low-risk patients with left bundle-branch block.

BACKGROUND: The abnormal left ventricular activation pattern in patients with a left bundle-branch block (LBBB) frequently induces myocardial perfusion defects, decreasing the specificity of noninvasive coronary-risk stratification with stress testing. We assessed the diagnostic and prognostic impact of gated single-photon emission computed tomography (SPECT) in low-risk patients with LBBB. METHODS: A total of 114 patients underwent dual-day protocol Tc-99m sestamibi gated SPECT and were divided into two subsets: without LBBB (group 1, n = 57) and with LBBB (group 2, n = 57). Sixty-eight (60%) patients had negative coronary angiography and 46 (40%) were at a low risk for coronary artery disease. The variables incorporating the extent and severity of perfusion defects were calculated: summed stress score, summed rest score and summed difference score, end-diastolic volume (EDV), end-systolic volume (ESV), and left ventricular ejection fraction. The mean variations in EDV and ESV were computed as follows: rest volume-poststress volume. Cardiac events were classified as major and minor. RESULTS: Gated SPECT was positive in eight (14%) patients of group 1 and 33 (58%) patients of group 2 (P<0.001). The summed stress score was significantly higher in group 2 than in group 1 (4.7 \ub1 4.8 vs. 0.9 \ub1 1.8, P<0.001); similarly, EDV and ESV were significantly higher in LBBB patients (P<0.05 in both). The mean variation in EDV was -2.21 ml for group 1 and 1.32 ml for group 2 (P<0.05). After a mean follow-up period of 32 \ub1 19 months, cardiac events occurred in 22 (23%) patients, six of group 1 and 16 of group 2 (12 vs. 35%, P