T-wave changes with intermittent left bundle branch block.

A 70-year-old woman was found to have an intermittent left bundle branch block. When her electrocardiogram showed normal conduction, T-wave inversions in leads V1-V3 appeared. These alterations suggested an anteroseptal infarction. However, the patient was asymptomatic, and the serum enzymes, technetium 99m pyrophosphate scan, and the thalium 201 scan were all negative. Thus the LBBB itself can produce T-wave in versions in the right precordial leads during the normal conduction phase which may simulate an acute myocardial infarction.