A Case of False-Positive Myocardial Perfusion Imaging in a Patient With Left Bundle Branch Block

False-positive myocardial perfusion imaging with left bundle branch block has been known for at least 10 years. The association with a rapid heart rate has not been emphasized in the past. The authors present a case of a 51-year-old woman with moderate hypercholesterinemia and hypertension who was referred for myocardial perfusion SPECT imaging because of a 4-month history of atypical chest pain. The resting electrocardiogram showed left bundle branch block (LBBB). She underwent a myocardial scanning in combination with coronary vasodilation using adenosine. During the infusion of adenosine, the patient did not report precardiac symptoms. The heart rate increased from 72 to 138 beats per minute, whereas the blood pressure decreased from 155/100 mm Hg to 140/95 mm Hg. Stress myocardial imaging exhibited extensive perfusion defects, whereas the images at rest showed improvement in all the observed defects. Because of the dramatic increase in heart rate during vasodilatation, the patient underwent repeat stress myocardial perfusion imaging with adenosine 2 weeks later while receiving beta-blocker medication. During adenosine infusion, there was only a minimal increase in heart rate from 68 to 77 beats per minute and scanning did not show myocardial ischemia.