This 64-year-old man is in hospital, recovering from a repair of a thoraco-abdominal aortic aneurysm:

• Marked sinus bradycardia, 38/min
• AV dissociation due an junctional escape rhythm (ventricular rate 43/min)
• One AV capture.
• Non-specific T wave abnormality

This is an example of AV dissociation due to the slowing of the proximal sinus pacemaker, that allows for the escape of the distal junctional pacemaker. The 2nd to 5th P waves do not conduct because of the AV node refractoriness caused by the junctional escape. As the QRS is faster, it eventually clears the P wave, that is allowed to conduct (with a prolonged PR interval).