This patient suffered a recent anterior-septal wall M.I., which can be seen as slight ST elevation in V1 and ischemic T wave inversions in V2 through V4. The patient has developed an intermittent left bundle branch block as a result of this M.I.  Every other beat is conducted in a left bundle branch block pattern, as the LBB cannot repolarize in time for each beat.  The criteria for LBBB are:  wide QRS, supraventricular rhythm, and negatively-deflected QRS in V1 with a positive QRS in V6 and Lead I.