FALSE-POSITIVE REVERSIBLE PERFUSION DEFECT DURING DOBUTAMINE-THALLIUMIMAGING IN LEFT-BUNDLE-BRANCH BLOCK

In the presence of pre-existing left bundle branch block (LBBB) exerci se stress thallium scans have been associated with false-positive sept al and apical perfusion abnormalities. Recent reports have documented a lower incidence of false-positive septal perfusion defects when phar macologic agents such as dipyridamole or adenosine are utilized in pat ients with LBBB. Dobutamine, a synthetic catecholamine, is being used with increasing frequency in combination with perfusion agents for the diagnosis of coronary artery disease in patients unable to achieve an adequate exercise workload. Because the positive inotropic and chrono tropic actions of dobutamine are similar to the physiologic effects of treadmill exercise, it is conceivable that false-positive perfusion a bnormalities will be observed in patients with preexisting LBBB underg oing dobutamine perfusion imaging. We describe a patient with underlyi ng LBBB who underwent dobutamine thallium imaging which revealed septa l and periapical defects. Subsequent coronary angiography showed these abnormalities to be false-positive. It is concluded that septal and p eriapical perfusion abnormalities during dobutamine thallium imaging m ay be false-positive and should be interpreted cautiously.