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