An implantable loop recorder (ILR) is a small, discreet device, often comparable in size to a USB drive or a AAA battery, inserted just under the skin of the chest. Its purpose is to continuously monitor and record the heart’s electrical activity over an extended period. This long-term monitoring helps diagnose infrequent heart rhythm abnormalities that shorter-term tests might miss.
Why It Is Used
Doctors recommend an ILR for individuals with symptoms suggesting an intermittent heart rhythm problem, such as unexplained fainting spells (also known as syncope), or recurrent sensations of a racing or fluttering heart (palpitations). Dizziness, lightheadedness, or even unexplained strokes can also prompt the use of an ILR. Because these symptoms occur sporadically, short-duration tests like a 24-hour Holter monitor often miss them. By continuously monitoring the heart for up to five years, the ILR significantly increases the chance of capturing these elusive events. This helps clinicians identify specific arrhythmias, like atrial fibrillation or unusually fast or slow heartbeats.
How It Records Heart Activity
The implantable loop recorder functions by continuously monitoring the heart’s electrical signals, similar to an electrocardiogram (ECG). It possesses internal memory that constantly records and overwrites heart rhythm data in a looping fashion. When the device detects an abnormal heart rhythm, based on pre-programmed parameters set by a physician, it “freezes” and stores that segment for later review. These parameters can include heart rates that are too fast or too slow, or irregular rhythms.
Patients can also manually activate the device to save a recording if they experience symptoms. A handheld activator, when placed over the device, instructs the ILR to save heart rhythm data from the moments immediately preceding, during, and after the symptom occurrence. Modern ILRs can store a significant amount of recorded data, with some capable of holding up to 60 minutes of recordings, including automatically saved segments and those triggered by the patient.
Implantation and Daily Life
Implanting an ILR is a straightforward, minor surgical procedure performed in an outpatient setting. The chest area, usually on the left side, is numbed with a local anesthetic, meaning the patient remains awake but experiences no pain during the procedure. A small incision is made, and a pocket is created under the skin for device insertion. The incision is then closed, and the procedure typically takes 10 to 30 minutes.
Most patients return home the same day. Mild soreness or discomfort at the incision site may occur for a few days to weeks. Daily life with an ILR is generally unaffected; the device is discreet and typically does not interfere with normal activities, including showering and exercise, once the incision has healed. Data from the ILR is usually transmitted wirelessly to the medical team via a bedside home monitor or smartphone app. Patients should carry an identification card, as the device may trigger metal detectors.
Device Removal and Follow-Up
An implantable loop recorder is a temporary diagnostic tool, and its removal is planned once sufficient heart rhythm data has been collected or a diagnosis has been established. The battery life of most ILRs ranges from approximately three to five years, after which removal is often recommended if not already done. The removal procedure is similar to the implantation, involving a small incision under local anesthesia to extract the device. This outpatient procedure typically takes about 15 to 30 minutes, and patients generally experience minimal discomfort.
After removal, the incision is closed, and patients can usually resume their normal activities within a day or two. Follow-up appointments are important to review the comprehensive data gathered by the ILR and to discuss any findings with the healthcare team. This analysis helps determine the underlying cause of the patient’s symptoms and guides decisions regarding further treatment or management strategies.