A Holter monitor is a portable device used to continuously record the electrical activity of the heart over 24 to 48 hours. It is typically worn on a belt or shoulder strap and is connected to electrodes placed on the skin. This monitoring helps doctors assess heart rhythms and detect irregularities that may not appear during a standard electrocardiogram (ECG). Patients are usually asked to maintain their normal activities while wearing the monitor, which allows for a more accurate representation of heart function in everyday situations. After the monitoring period, the data is analyzed by a healthcare professional to identify any potential heart issues.