This example of previous anterior wall M.I. with right bundle branch block is from a 90-year-old man. He survived an anterior-septal M.I. caused by an occlusion of the left anterior descending branch of the LCA. The septum was involved in the damaged area, and the patient was left with a right bundle branch block. The pathological Q waves in Leads V1 through V3 show the location of permanent damage, or necrosis.
In this case, the usual rSR' pattern of right bundle branch block is replaced by qR, indicating loss of the initial r wave due to the M.I.
Review of RBBB criteria: wide QRS, rSR' pattern in V1, and Rs with a slurred s wave in I and V6. These criteria must be present in a SUPRAVENTRICULAR rhythm to diagnose RBBB.