It's a modest device that keeps track of your heart rate for a set period of time, usually 24 to 48 hours. The battery-powered device is small enough to fit in a backpack or small handbag. It is connected to electrodes through cables or adhesive patches placed on your chest. Because irregular heartbeat issues rarely show up on a traditional EKG or during a doctor's check-up, this appears to be effective. A Holter monitor test, for example, can assist your doctor in determining why your heart rate rises when you lie down to sleep at night. As a result, the need for holter monitoring devices is increasing