What precautions should be taken for a patient with a redundant loop recorder (implantable loop recorder) undergoing a brain Magnetic Resonance Imaging (MRI) scan?

MRI Safety with Implantable Loop Recorders

Patients with implantable loop recorders can safely undergo brain MRI, but the device must be interrogated before and immediately after scanning to clear the memory and verify device integrity, as MRI consistently produces artifacts that mimic both tachycardia and bradycardia which could be mistakenly interpreted as true arrhythmic events. 1, 2

Pre-Scan Protocol

Before the MRI scan:

• Clear the ILR memory completely to distinguish true arrhythmic events from MRI-induced artifacts 1, 2
• Verify signal integrity and time-date stamp functionality 1
• Document all programmed parameters and battery status 1
• Do not alter any programmed settings 2

Safety Profile During Scanning

The physical safety of scanning is well-established:

• No patient harm, device movement, heating at the implant site, or sensations of tugging occur during MRI 1, 2
• No permanent damage to the ILR device occurs 1
• Signal integrity, programmed parameters, battery status, and device communication remain intact post-scan 1
• The device can be reprogrammed normally after MRI 1

This safety profile has been demonstrated across multiple anatomical scan locations including cranial, lumbar spine, shoulder, and knee MRI 1, 2, 3

Critical Artifact Issue

The major clinical concern is artifact generation, not device safety:

• Artifacts mimicking both bradyarrhythmias and tachyarrhythmias appear in all patients undergoing MRI with an ILR, regardless of scan location 1, 2, 3
• These artifacts can mimic both wide complex and narrow complex tachycardias 3
• Shoulder MRI may produce more artifacts than cranial MRI 3
• These artifacts must be excluded from clinical interpretation to avoid mistakenly attributing syncope or palpitations to false arrhythmic events 1, 2

Post-Scan Protocol

Immediately after MRI completion:

• Reinterrogate the device to verify all parameters remain unchanged 1, 2
• Confirm signal integrity and battery status 1
• Clear any artifact-generated recordings from the device memory 1, 2
• Question the patient about any symptoms experienced during the scan 1

Context Within Broader MRI Safety Guidelines

The Association of Anaesthetists guidelines classify implantable programmable devices as requiring careful evaluation, noting that neurostimulators and similar devices may be affected by radiofrequency and magnetic fields 4. However, ILRs differ fundamentally from neurostimulators and pacemakers in that they are purely diagnostic monitoring devices without therapeutic function, making them inherently safer for MRI exposure 1, 2.

Common Pitfall to Avoid

The single most important pitfall is misinterpreting MRI-induced artifacts as true arrhythmic events. If a patient with an ILR reports syncope or palpitations during the period when MRI was performed, clinicians must recognize that any recorded "arrhythmias" during the scan time are artifacts, not true cardiac events 1, 2, 3. Failure to recognize this could lead to unnecessary interventions such as pacemaker implantation or antiarrhythmic therapy based on false data.