A looping memory monitor records ECG activity for a given period of time. When the patient experiences symptoms, he pushes a button to activate the device, which triggers the monitor to record the 60 seconds prior to the event, the event, and up to 40 seconds following.
This gives doctors insight into what was going on before and after an event happened. By studying these recordings, they can determine whether there was a change in heart rhythm or other abnormalities that may have led to a symptom.