Ambulatory ECG Monitoring
Ambulatory ECG monitoring is an extended recording of the heart’s electrical activity, used to capture intermittent symptoms such as palpitations, dizziness or blackouts. A standard resting ECG only records about ten seconds; if symptoms occur intermittently, that snapshot will almost always be normal. Ambulatory monitors record continuously for hours, days, or even years, dramatically increasing the chance of catching the rhythm during an episode.
What are the different types of ambulatory monitor?
The right type of monitor depends on how often the symptoms occur.
- 24- to 48-hour Holter monitor — a small box worn on a belt or strap, connected to three or four sticky electrodes on the chest. Records continuously for one or two days. Best when symptoms are happening every day.
- 7- to 14-day patch monitor — a single small adhesive patch worn on the chest with no separate wires. Modern patches are waterproof and can be worn during exercise and sleep. The standard middle-ground monitor for symptoms that occur every few days to weekly.
- External event recorder — a device worn for several weeks that the patient activates when symptoms occur. Less commonly used now that patch monitors are widely available.
- Implantable loop recorder (ILR) — a small device, around the size of a USB stick, inserted just under the skin in the upper chest under local anaesthetic. It records continuously for up to several years and is used when symptoms are infrequent — for example unexplained blackouts every few months — but where the diagnosis is important.
What can ambulatory monitoring detect?
- Atrial fibrillation, both established and paroxysmal
- Supraventricular tachycardia (SVT)
- Ventricular ectopy and ventricular tachycardia
- Significant pauses (sinus pauses, AV block)
- Bradycardia and tachycardia patterns
- Correlation of symptoms with the heart rhythm — sometimes the most useful information is that an episode of palpitations occurred while the rhythm was completely normal
What can I expect?
For a Holter or patch, the device is fitted in a quick clinic appointment, with brief instructions on how to keep a symptom diary. You wear it for the prescribed period, then return it. The data is uploaded to a secure server and reported by a cardiologist within a few working days.
For an implantable loop recorder, the device is inserted under local anaesthetic in a quick procedure (usually about 15 minutes). A small incision is made just under the skin, the device is positioned, and a single dissolvable suture closes the wound. The device transmits data wirelessly to a secure portal, with automatic alerts if a significant rhythm event is detected.