Medically reviewed by Dr Nabila Laskar, Consultant Cardiologist (GMC 7040901). A Holter monitor is a small, portable ECG device worn for 24 hours to 7 days that continuously records your heart's rhythm during normal daily activity — capturing problems a single in-clinic ECG would likely miss.
Because it records continuously over an extended period, a Holter monitor is particularly effective at catching intermittent arrhythmias — atrial fibrillation, ectopic beats, supraventricular tachycardia, and pauses in heart rhythm — that occur unpredictably and would likely be missed by a 10-second resting ECG.
Typically recommended for unexplained palpitations, dizziness or blackouts, monitoring known arrhythmias, or assessing the effectiveness of heart rhythm medication. For more detail on what causes palpitations see /conditions/heart-palpitations. The duration (24-hour, 48-hour, or 7-day) is chosen based on how frequently your symptoms occur.
The monitor is fitted with small adhesive electrodes on the chest connected to a lightweight recorder, worn under clothing. You continue normal daily activities — work, exercise, sleep — and keep a diary noting any symptoms experienced, which is matched against the recording afterwards. Showering arrangements depend on the specific device used.
Once returned, the recording is analysed and correlated against your symptom diary entries. Dr Laskar reviews the full report and explains the findings, with a written report provided and next steps discussed if any rhythm abnormality is identified.
Typically 24 hours to 7 days, depending on how often your symptoms occur — more frequent symptoms generally need shorter monitoring, while infrequent symptoms benefit from longer wear time.
This depends on the specific device. Some modern patch-style monitors are water-resistant; traditional wired monitors typically need to be kept dry. You'll be given specific instructions for your device.
No. You're encouraged to go about your normal routine — work, exercise, sleep — exactly as you would otherwise, since the point is to capture your heart's rhythm during typical daily life.
If symptoms don't occur during the monitoring window, your cardiologist may recommend a longer recording period or a different type of monitor, such as an implantable loop recorder for very infrequent symptoms.