A Holter monitor is a small, wearable device that continuously records the heart’s electrical activity (ECG) over a period of 24 hours, 48 hours, 7 days, or occasionally longer. It is used to detect arrhythmias that may be intermittent and therefore not captured by a standard resting ECG, which records only a few seconds of heart rhythm.
The patient wears several sticky electrode patches on the chest, connected by wires to a small recording device clipped to a belt or carried in a pocket. The device records continuously while the patient goes about normal daily activities, which may trigger symptoms or arrhythmias that would not occur at rest. Most Holter protocols ask patients to keep a diary of symptoms (palpitations, dizziness, chest pain, blackouts) with the times they occurred. After the monitoring period ends, the recorder is returned to the clinic, where technicians and cardiologists analyse the recording and correlate any arrhythmias with the diary entries.
After cardiac arrest, Holter monitoring may detect intermittent arrhythmias, assess the frequency of ventricular ectopic beats, monitor for non-sustained ventricular tachycardia, and evaluate the effectiveness of antiarrhythmic medication. If symptoms occur infrequently (for example, once a month), even a 7-day Holter may not capture a relevant episode; longer-term monitoring with an implantable loop recorder is then more appropriate.
Holter monitoring is safe, non-invasive, and can be performed as an outpatient. The electrode patches must be kept dry (no swimming or bathing), and some patients find the wires and recorder slightly cumbersome for the duration of the recording.
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