A Holter monitor is used to record a digital, continuous EKG tracing (recording of the electrical activity) of the heart. The small monitor, about the size of a deck of cards, is hooked to electrodes that are placed on your chest. The monitor is connected at the hospital. Once you return home, you wear the monitor for 24 to 48 hours. When you return to the hospital, a physician reviews the EKG tracing for any abnormal electrical activity.