A Holter monitor is a device that records your heart’s rate and rhythm, usually over a period of 24 to 48 hours. The monitor is a small, box-shaped electronic device that is connected with wires (leads) to sticky patches (electrodes) that are placed on the skin of your chest. The monitor is attached to a strap around your shoulder or waist to hold it close to your body.
A Holter monitor, like an electrocardiogram (ECG or EKG), reads your heart’s electrical activity. Your heart has an electrical system that functions like a natural pacemaker. Electrical signals travel through the heart's chambers to cause it to beat. If the heart’s natural electrical system is not functioning correctly, an abnormal heartbeat (arrhythmia) may result. This may cause symptoms of your heart racing, palpitations, or feeling faint.