This electrocardiogram shows complete right bundle branch block. The characteristic features demonstrated here include a wide QRS complex greater than twelve hundredths of a second; a large R' in leads V1, V2 and aVR, reflecting delayed right ventricular activation; and ST-T wave abnormalities seen in the same leads. While right bundle branch block is an electrocardiographic abnormality, it may also occur in patients with no significant underlying cardiac disease.