Written by Dimitrios Vrachatis, Specialist Cardiologist, PhD, National and Kapodistrian University of Athens.
What is an implantable loop recorder?
An implantable loop recorder (ILR), sometimes called an implantable Holter, is a device implanted in the body to monitor the heart rhythm.
What is an implantable loop recorder used for?
It is used to investigate symptoms such as palpitations or clinical events such as fainting, to diagnose arrhythmias such as atrial fibrillation after a stroke, or to monitor the response to ablation of atrial or ventricular arrhythmias.
An ILR is usually chosen when symptoms or the suspected arrhythmia occur infrequently, making diagnosis practically impossible within the limited recording period of an external 24- or 48-hour Holter.
How does it work?
The device continuously records the heart rhythm as a single-lead ECG and has specialised software to detect fast or slow arrhythmias.
Using a small remote control the size of a keyring, the patient or a relative can also instruct the device to mark the electrocardiogram at the moment a symptom is felt.
How does the cardiologist receive the information?
The treating doctor periodically checks the recordings using a dedicated programmer. Remote monitoring is also possible through specialised software and a device.
How is it implanted?
The patient lies on their back and the chest is uncovered. Hair is removed locally if necessary, the skin is cleaned with antiseptic and a small amount of local anaesthetic is injected using a fine needle.
The device is then implanted under the skin to the left of the sternum using a dedicated insertion tool: in simple terms, it is loaded into a special syringe-like instrument and advanced beneath the skin with a plunger.
The procedure takes less than 30 minutes. The patient returns to their usual activities the same day.
How large is it?
The device is rectangular and smaller than a pen cap or an AA battery.
Are there complications?
Local complications, such as a haematoma or infection, are possible in theory, but are very rare. The most common issue is local pain for a short period after implantation, managed with simple painkillers.
What preparation is needed?
No special preparation is required before ILR implantation. Your treating physician will provide instructions in every case.
How long does it last?
ILR devices can record the heart rhythm for long periods — approximately 3–4 years.
When is the device removed?
The implantable Holter is removed through a simple procedure similar to implantation: a small skin incision is made and the device is taken out using small forceps.
It can be removed when its purpose has been achieved and the patient wishes it — for example, after the relevant arrhythmia has been diagnosed — or when the battery reaches the end of its life, usually after 3–4 years.
Can I have an MRI scan?
These devices are compatible with MRI and do not interfere with any other diagnostic or therapeutic examination that may be needed.