Unusual manifestation of left ventricular electrical conduction delay on the surface 12-lead electrocardiogram in a patient with prior myocardial infarction.

We describe a 41-year-old man with a prior history of myocardial infarction, whose surface 12-lead electrocardiogram did not show typical left bundle-branch block pattern or wide QRS complex. However, electrophysiological study showed distinct left ventricular electrical conduction delays. The surface 12-lead electrocardiogram modified to the paper at 50 mm/s and double standard (20 mm equals 1 mV) revealed obvious notches of the terminal forces of the QRS in leads II, III, aVL, aVF, V3, V4, V5, and V6, these might be partially consistent with left ventricular electrical conduction delay in the scar lesion of the infero-posterior of the ventricle.