Cardiology• Updated 21 October 2026
Holter Monitor (24-hour ECG)
A portable ECG worn for 24 hours or longer to record the heart rhythm during daily life.
Results: A few days
Quick Summary
Primary Purpose
To find rhythm problems that come and go, such as palpitations or fainting.
What It Measures
Continuous heart rhythm.
Preparation
Shower before fitting; you can't usually shower while wearing it.
Overview
You carry on with normal activities and keep a diary of symptoms.
Longer monitors are used for infrequent symptoms.
What It Measures
Rhythm over time
Irregular or fast beats.
Symptom link
Matches diary times.
How It's Performed
- 01
Fitting
Electrodes and a small recorder.
- 02
Wear
For 24–48 hours or longer.
- 03
Return
The device is removed and analysed.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Holter monitor (24h)(opens in a new tab) · MedlinePlus, US National Library of Medicine
- Electrocardiogram (ECG)(opens in a new tab) · NHS