A 44-year-old white male who developed third-degree heart block during cardiac catheterization is presented. Right heart catheterization precipitated bifascicular block, right bundle branch block with left posterior hemiblock, and resulted in third-degree heart block during the left heart procedure. It is recommended that multiple electrocardiographic lead monitoring be considered during cardiac catheterization in order to recognize more easily high-risk conduction disturbances, ie a bifascicular block pattern with frontal plane axis shifts.