Dobutamine thallium-201 myocardial SPECT in patients with left bundle branch block and normal coronary arteries

Dobutamine is a positive inotropic and chronotropic agent and is being widely used as a pharmacologic stress agent in patients unable to achieve maximal dynamic exercise test. The purpose of the current study was to document the dobutamine induced false-positive septal defect in terms of its frequency and extent on 201Tl myocardial SPECT in patient with left bundle branch block (LBBB).

Twenty-five symptomatic patients with LBBB underwent dobutamine and redistribution 201Tl myocardial SPECT studies. Coronary angiographies were also performed. Only those patients with normal coronaries (n = 19) were included in the study. For each study, tomograms were divided into 19 segments, and each segment was analyzed qualitatively as to presence and type of perfusion defect (reversible or fixed). In addition, septal perfusion was scored in each patient (1 = markedly, 2 = moderately reduced, 3 = normal uptake).

Sixteen of 19 patients (84.21%) had false-positive septal reversible perfusion defect, and the remaining 3 had normal images. Perfusion defects were confined to only the septum in 5 of 16 patients (31.25%), whereas a greater proportion of patients had septal defect extending to the contiguous myocardial areas, mainly to the anterior wall. Five of 16 patients with false-positive defects had a septal perfusion score of 1, while the remaining 11 had a score of 2.

Dobutamine myocardial scintigraphy in patients with LBBB was misleading for the diagnosis of coronary artery disease, since up to 84.21% of patients had false-positive septal perfusion defects.