Event recorder or implantable loop recorder

What are event recorders and implantable loop recorders?

These are heart-rhythm monitors that record the electrical activity of your heart over a long period, so a doctor can match what your heart is doing to symptoms such as blackouts (fainting), dizziness or palpitations. They are used when a standard ECG, which lasts only seconds, or a 24-hour to 7-day tape has not caught the problem, because the symptoms happen too rarely.

An external event recorder is worn on the body and records when you press a button or when it detects an abnormal beat; it is used for weeks. An implantable loop recorder (ILR), also called an insertable cardiac monitor, is a small device, around the size of a memory stick, placed just under the skin of the chest under local anaesthetic. It records continuously on a loop and can stay in place for up to about three to four and a half years.

The purpose is to find out whether your symptoms are caused by a heart-rhythm problem, and if so which one. The monitor is a diagnostic device only: it records and reports, but does not treat or correct the rhythm. A normal recording during a symptom is itself useful, because it can rule the heart out as the cause.

Types, options & approaches

There may be different ways to do this. The right approach depends on the clinical question and your circumstances.

Worn recorder versus implanted recorder

Your cardiologist chooses the monitor based on how often your symptoms happen and how serious the suspected problem is.

Preparing for your test

• Ask which type of monitor is planned and why, and how long you will wear or keep it.
• Keep a simple symptom diary with dates and times, as matching symptoms to the recording is what gives the answer.
• For an implant, tell the team about any blood-thinning medicines, allergies (including to skin glue or local anaesthetic) and any history of wound or skin infection.
• For an implant, you can usually eat and drink normally beforehand unless told otherwise.
• Wear a loose top on the day of an implant, and arrange a way to get home, though you can usually travel yourself.
• Ask how the device sends data, whether you need a bedside transmitter, and who to contact if it alerts.
• Check how to use the patient activator or smartphone app so you can mark an episode when symptoms strike.

What happens

For an external recorder, a cardiac physiologist attaches electrodes or a patch and shows you how to record an episode. You then carry on with normal life and return the device when the recording period ends.

For an implantable loop recorder, a small area of skin on the left side of the chest is cleaned and numbed with local anaesthetic. A tiny cut, usually one to two centimetres, is made and the device is placed just under the skin. The wound is closed with glue, steri-strips or a stitch. The procedure usually takes about 15 minutes and you are awake throughout.

Afterwards, the device records your heart rhythm automatically, and you can also trigger a recording when you feel symptoms. Recordings are downloaded at clinic visits or sent automatically to the hospital through a transmitter, where a specialist reviews them.

Is this test right for me?

A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.

Before you decide

Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.

Comfort, sedation or contrast choices

If local anaesthetic, sedation, contrast or pain relief is used, ask what is planned, why, and what it means afterwards.

The implant procedure itself is low-risk and very commonly done; infection is the main thing to watch for and is uncommon. The bigger practical limitation is patience: symptoms may not happen for weeks or months, so the answer can take time. Ask your team how long they expect to monitor before reviewing, what counts as a useful result, and what happens if nothing is captured.

Published figures to discuss

The implant procedure is low-risk and very commonly done, so robust complication percentages are limited and most reported problems are minor and local. The main uncertainty is diagnostic yield: how likely the monitor is to capture a symptom depends entirely on how often symptoms happen and how long monitoring lasts. Because of this, rates are best treated qualitatively.

These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.

What happens afterwards

There is no real physical recovery from an external recorder. After an implant, you may have minor soreness or bruising for a few days; the answer to your symptoms comes whenever a relevant episode is recorded, which may be weeks or months away.

• Mild bruising, tenderness or a small lump at the implant site, with a small skin mark from the cut that fades over months.
• Itchy or slightly red skin under an external patch or electrodes.
• Feeling aware of the device under the skin at first.
• Long quiet stretches with no symptoms and no alerts.

Aftercare

• Keep the implant wound clean and dry, and follow the advice you are given about showering and dressings.
• Avoid heavy lifting and vigorous arm movement on that side for a few days after an implant.
• Use the patient activator or app to mark an episode whenever you have symptoms.
• Keep your bedside or mobile transmitter set up and connected if you have one.
• Keep a symptom diary and bring it to clinic visits.
• Carry your device identification card, which is useful for airport security and other medical tests.
• Contact the clinic if you notice signs of infection or if the wound opens.
• Tell any healthcare professional you have an implant before an MRI scan or other imaging.

• Symptom diary ready, with space for dates and times
• Know how to use the patient activator or smartphone app
• Bedside transmitter set up at home if provided
• Loose, comfortable top for the day of an implant
• Way to get home arranged
• Clinic and out-of-hours contact numbers saved
• Device identification card kept safe

⚠ Get urgent help if…

• Spreading redness, swelling, heat, pain or discharge at an implant site, which can suggest infection.
• The wound opening or the device starting to come through the skin.
• A high temperature or feeling generally unwell after an implant.
• Fainting or a blackout, especially with injury; treat as urgent and seek help.
• Chest pain, severe breathlessness, or palpitations with collapse, which need emergency care.
• A very fast, very slow or wildly irregular pulse with feeling faint.

Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.

General guidance — it doesn't replace the specific advice your specialist gives you.

Results & realistic expectations

The monitor gives an answer when it records your heart rhythm at the time you have symptoms. A clear recording showing an abnormal rhythm during a blackout or palpitation can confirm the cause and point to treatment. A normal recording during symptoms is also a real result, because it suggests the heart rhythm is not to blame and other causes can be looked at.

The limitation is timing. If no symptoms happen while you are monitored, the test may be inconclusive and need to continue or be repeated. The device cannot predict the future or rule out every possible problem, only what it captures while recording.

An external recording reflects only the period it was worn. An implantable loop recorder keeps working until a diagnosis is made or the battery runs down, typically up to about three to four and a half years. Once the question is answered, an implant can usually be removed, or safely left in place. If symptoms change or return later, your cardiologist may suggest fresh monitoring.

Related tests, treatments or support

Rhythm monitoring is often used alongside other heart tests, such as an ECG, echocardiogram, exercise test or blood tests, to build a fuller picture. After an unexplained stroke it may be combined with brain and vascular imaging arranged by the stroke team.

Follow-up & long-term care

External recordings are analysed after the device is returned, and you are told the result, usually within a few weeks. With an implant, recordings are reviewed at scheduled clinic visits or sent automatically through a transmitter, and the clinic contacts you if an important rhythm is detected. Make sure you know who to call and how the result will reach you.

• Keep any bedside or mobile transmitter switched on and connected so recordings are sent.
• Attend scheduled device checks so the battery and recordings can be reviewed.
• Replace or recharge the patient activator as advised.
• Tell future clinicians about the implant before MRI or other imaging.
• Arrange removal once the device is no longer needed, if recommended.

Repeat, follow-on and what comes next

• Monitoring may need to continue longer than planned, or be repeated, if symptoms are not captured.
• An implant occasionally needs repositioning or earlier removal because of discomfort, skin problems or infection.
• An inconclusive result may lead on to a different test rather than a clear diagnosis.

Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.

What good aftercare looks like

• Clear, written wound-care instructions and signs of infection to watch for after an implant.
• A named contact route for questions, symptoms or device alerts.
• A defined review schedule and a plan for remote data transmission.
• Plain advice on what happens if monitoring is inconclusive.
• A device identification card and guidance for MRI and airport security.

What affects the cost

Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:

• The type of monitor: an external recorder or patch versus an implanted device.
• Whether a small procedure to insert an implant is needed, including the operator's time and the room or theatre used.
• The device itself and any bedside or mobile transmitter.
• How long monitoring lasts and how often recordings are reviewed.
• The specialist reporting and any follow-up consultations to discuss results.
• Removal of an implant later, if needed.

• The fee for the cardiologist or operator fitting or supervising the monitor.
• The device and any transmitter, and whether these are included.
• Any facility or procedure-room fee for fitting an implant.
• Local anaesthetic and wound-care costs for an implant.
• How recordings are reviewed and reported, and how results reach you.
• Follow-up consultations to discuss results.
• What happens, and what it costs, if the monitor is inconclusive or needs removing.

On the NHS? Heart rhythm monitors are widely available on the NHS when an intermittent rhythm problem or unexplained blackout is being investigated; private monitoring is sometimes chosen for speed or convenience.

You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.

Consent traps and marketing red flags

These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.

Choosing a specialist safely

• Check the specialist is on the GMC Specialist Register for this area.
• Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
• You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
• Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
• You're entitled to your total cost in writing — including any follow-up — before you decide.

How Vuemedics verifies every consultant →

Take this to your consultation. A good specialist will welcome every one of these.

• Which type of monitor do you recommend for me, and why that one?
• How long do you expect to monitor before reviewing the results?
• What will the result change about my treatment or driving?
• What happens if no symptoms are recorded during the monitoring period?
• How will recordings reach you, and who do I contact if I have symptoms or an alert?
• If I have an implant, when can it be removed, and is the device MRI-conditional?
• Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
• Will you be the specialist who carries out my test, and who looks after me afterwards?
• What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
• What does a realistic result look like — and what can this test not achieve?
• What are my options, including waiting, doing nothing for now, or choosing a different approach?
• Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
• What is the total cost in writing, including any follow-ups, and how much time do I have to decide?

Find a verified specialist for event recorder or implantable loop recorder

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How we made this page

Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →

Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.

Sources & standards: British Heart Foundation — Implantable loop recorders NHS — Atrial fibrillation diagnosis (heart rhythm monitoring) University College London Hospitals NHS — Implantable loop recorder (ILR) Cambridge University Hospitals NHS — Implantable loop recorder (Reveal LINQ) NICE — Atrial fibrillation: diagnosis and management (NG196)

Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.

Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.