Implantable loop recorder (ILR)

What is an implantable loop recorder?

An implantable loop recorder (ILR) is a miniature heart monitor, smaller than a house key and slimmer than a pen, placed just under the skin of the chest in a few minutes under local anaesthetic. It continuously records your heart's electrical activity for up to four years, automatically storing any abnormal rhythm it detects and any episode you mark yourself using a handheld activator or smartphone app when symptoms strike. Recordings are transmitted from home to the clinic, so significant findings reach us without you lifting a finger.

The ILR solves the fundamental problem of intermittent symptoms: a rhythm disturbance that happens once a month will almost never coincide with a 24-hour monitor. With an ILR, the monitor is always on.

When is an ILR recommended?

• Unexplained blackouts (syncope): when faints or collapses remain unexplained after initial assessment, including a tilt table test, an ILR is the definitive way to prove, or exclude, a rhythm cause such as dangerous pauses or heart block, findings that lead directly to curative pacemaker treatment.
• Infrequent palpitations: capturing the rhythm during rare but troubling episodes that repeated ambulatory ECG monitoring has failed to catch. See our palpitations page.
• After unexplained stroke: silent, intermittent atrial fibrillation is a common hidden cause of stroke; prolonged monitoring with an ILR detects it far more often than short-term monitors, and a positive finding changes treatment, anticoagulation, immediately.
• Monitoring known rhythm disorders: quantifying AF burden after ablation or guiding therapy in selected inherited conditions.

How does it compare with other monitors?

Short-term monitors remain the right first step for frequent symptoms: a 24-hour to 14-day ambulatory ECG catches anything that happens most days or weeks. Consumer wearables can be helpful but record intermittently and imperfectly. The ILR's advantage is continuous, medical-grade surveillance measured in years, with automatic detection you do not have to trigger, which is why it is the gold standard for infrequent, high-stakes symptoms.

What happens at implantation?

Fitting an ILR is one of cardiology's smallest procedures: a day-case visit of around thirty minutes, local anaesthetic over the upper left chest, an incision under a centimetre, and the device slipped just beneath the skin, no leads, no stitches beyond skin closure, and usually only paracetamol needed afterwards. You go home the same hour with a home transmitter or smartphone pairing set up, and normal activity, including exercise and travel, resumes almost immediately. The device is invisible to most eyes, MRI-conditional, and airport-safe.

Living with your ILR and getting answers

Day to day you will forget it is there. When symptoms occur, you mark the moment on the activator or app; the device also files anything significant automatically and transmits overnight from home. Every recording is reviewed, and you are contacted promptly about findings that matter. When the diagnostic question is answered, or at the end of battery life, the recorder is removed through the same tiny incision in minutes. Risks are minimal: occasional bruising, and uncommonly minor site infection or the device working loose.

Frequently asked questions

Will the loop recorder hurt or show?

Implantation involves a minute or two of pressure under local anaesthetic; most patients need nothing more than paracetamol afterwards. The device sits flat under the skin of the upper chest and, in most people, is barely visible, a faint outline you would have to look for.

Can I exercise, swim and shower normally?

Yes. Keep the small wound dry for the first few days; after that, showers, baths, swimming, gym work and sport all continue as normal. The recorder is designed for real life, because real life is exactly what it needs to observe.

Is an ILR safe with airport scanners and MRI?

Yes. Airport security is no obstacle, carry your device card and walk through normally, and current loop recorders are MRI-conditional, meaning scans can be performed under standard protocols. Mobile phones and household electronics cause no problems.

How long does the battery last, and what happens then?

Current devices monitor continuously for up to four years. If the diagnostic question is answered sooner, the recorder is simply removed; if the battery reaches its end first, we review what has been learned and decide together whether a replacement is worthwhile.

Who actually looks at my recordings?

Transmissions from your home monitor are reviewed by the cardiac physiology team, with anything significant escalated to Dr Assomull promptly. You are contacted about findings that matter, and urgent abnormalities trigger a same-day call, so you are never left wondering.

Will I feel it recording?

No. The device has no leads and delivers no impulses; it simply listens. Most patients report forgetting it is there within a fortnight, which is precisely the point.

Is my smartwatch not enough?

Wearables are genuinely useful and we take their recordings seriously, but they sample intermittently, depend on being worn and charged, and their single-lead traces are not always diagnostic. An ILR records continuously to medical-grade standards, captures events during sleep, showers and exercise, and detects abnormalities automatically whether or not you notice symptoms. For high-stakes questions, blackouts, suspected silent atrial fibrillation after a stroke, the two are not equivalent, though they can work well together.

Why choose Dr Assomull?

The value of an ILR lies in the judgement around it: choosing the right patients, programming the right detection settings, and acting decisively on what it finds. Dr Assomull leads that whole pathway at 68 Harley Street, assessment, same-week implantation, continuous remote follow-up, and a clear plan the moment your answer arrives, whether that is a pacemaker, ablation referral, anticoagulation or firm reassurance.

If unexplained blackouts or elusive palpitations need an answer, book a consultation, usually available within one working day.