The Holter Monitor is a continuous tape recording of a patient's EKG for 24 hours.  This data will help the physician evaluate the type and/or amount of irregular heart beats during a patient's regular daily activities, as well as correlate symptoms of dizziness, palpitations or blackouts.  Since the recording covers 24 continuous hours, Holter monitoring is much more likely to detect an abnormal heart rhythm in comparison to a regular EKG, which lasts less than a minute.