An implantable loop recorder (ILR) is a small device (usually the size of an USB thumbdrive) that is implanted underneath the skin of the chest to the left of the breastbone. It serve as a continuous ECG-recording machine to capture any abnormal heart rhythm. The device has a two to three years battery life allowing for long term and constant monitoring, giving the cardiologist ample opportunity to capture any abnormal heart rhythm.

It is recommended for patients who experience symptoms such as syncope (fainting), seizures, recurrent palpitations, or dizziness. ILR is best used in patients who experience these symptoms often but not regular enough to be captured by a 24-hour or 30-day external monitor.

The implantation is performed in a procedure lab by an electrophysiologist under local anaesthesia. A small incision (about 1-2cm) is made at the chest area, just left of the breastbone and the ILR is inserted under the skin with no wires inserted into the heart. On average, the procedure last about 20 to 30 minutes and patients can go home the same day with almost no restrictions on activity or work.