The Holter monitor is a type of electrocardiogram (ECG or EKG) used to monitor the ECG tracing continuously for a period of 24 hours or longer. An ECG is one of the simplest and fastest procedures used to evaluate the heart. Electrodes (small, plastic patches) are placed at certain locations on the chest and abdomen. When the electrodes are connected to an ECG machine by lead wires, the electrical activity of the heart is measured, interpreted, and printed out for the physician's information and further interpretation.
When symptoms such as dizziness, fainting, low blood pressure, prolonged fatigue, and palpitations continue to occur without a definitive diagnosis obtained with a resting ECG, an exercise ECG, or a signal-averaged ECG, your physician may request an ECG tracing to be run over a long period of time, using the Holter monitor.
Certain dysrhythmias/arrhythmias (abnormal heart rhythms), which can cause the symptoms noted above, may occur only intermittently, or may occur only under certain conditions, such as stress. Dysrhythmias of this type are difficult to obtain on an ECG tracing that only runs for a few minutes. Thus, the physician will request a Holter monitor to allow a better opportunity to capture any abnormal beats or rhythms that may be causing the symptoms. The Holter monitor records continuously for the entire period of 24 to 48 hours. Some Holter monitors may record continuously but also have an event monitor feature that you activate when symptoms begin to occur.
You will receive instructions regarding how long you will need to wear the recorder (usually 24 to 48 hours), how to keep a diary of your activities and symptoms during the test, and personal care/activity instructions.