This is an electrocardiogram from an elderly man with a history of syncope. This electrocardiogram shows sinus rhythm at 74 per minute. The PR interval is grossly prolonged at 288 milliseconds, there's an R S R complex in V1 compatible with a right bundle branch block and a QRS axis of minus 83 degrees compatible with a left anterior hemi-block. Taking all three abnormalities together the tracing suggests a trifasicular block. This patient also had a Holter monitor that showed second-degree heart block and as a result a pacemaker was implanted because of his history of syncope.