Answer for July 8, 2013
Right bundle branch block (RBBB). The QRS is at least 0.12 sec wide (3 little boxes), with an rsR' in V1. Normally, there is also a slurred s or S wave in V6, not seen here, but is present in left-sided lead I. Make sure you are clear on the 'picture' of the RBBB as compared with LBBB. If not clear, take a look at Classic LBBB.
NOTE: EKG's are for internal educational purposes of the University of Massachusetts Department of Family Medicine. Please do not forward without permission from Dr. Golding!