MRI Safety Protocols for Patients with Pacemakers

General Safety

• A standardized protocol—including pre‑scan device interrogation, appropriate programming, continuous ECG monitoring during the scan, and post‑scan reprogramming—allows safe 1.5 Tesla shoulder MRI in patients with both MRI‑conditional and non‑conditional pacemakers. Strong recommendation (high‑quality evidence). 1

MRI‑Conditional Pacemakers

• Scanning should be performed at 1.5 Tesla when feasible, with the device set to an MRI‑compatible mode. Strong recommendation. 2
• The device team must interrogate the pacemaker before the scan to verify rhythm stability, recent arrhythmias, and sensing thresholds, then program it to MRI‑compatible mode. Strong recommendation. 3
• Newer systems may auto‑detect the MRI environment and switch to a safe mode, but a post‑scan interrogation remains mandatory. Strong recommendation. 3
• After imaging, the device must be reprogrammed to its pre‑scan settings to confirm lead integrity and restore normal pacing parameters. Strong recommendation. 3

Non‑Conditional (Legacy) Pacemakers

Overall Safety

• Large prospective studies (each >1,500 patients) have shown that 1.5 Tesla MRI is safe in non‑conditional pacemaker recipients, with only 0.6 % experiencing a transient electrical reset. High‑quality evidence. 1
• A meta‑analysis of >5,000 patients with non‑conditional devices reported low adverse‑event rates and no induction of atrial or ventricular arrhythmias. High‑quality evidence. 4

Patients Without Pacemaker Dependency

• The device should be programmed to a sensing‑only mode before scanning. Strong recommendation. 1

Patients With Pacemaker Dependency

• The device must be programmed to an asynchronous pacing mode (e.g., AOO, VOO, DOO) before scanning. Strong recommendation. 1
• Continuous ECG monitoring and the presence of an ACLS‑trained practitioner are required throughout the examination. Strong recommendation. 5
• A meta‑analysis of 511 pacemaker‑dependent patients confirmed safety of this protocol. High‑quality evidence. 3

Mandatory Protocol Components

Pre‑Scan Requirements

• Mandatory device interrogation to determine pacemaker dependency, sensing thresholds, and pacing thresholds. Strong recommendation. 4
• Review of imaging (e.g., chest radiography) to identify lead extenders, retained epicardial leads, abandoned transvenous leads, or fractured leads. Strong recommendation. 2
• Patients with lead extenders or fractured leads are contraindicated for MRI. Strong recommendation. 2
• MRI may be considered in patients with epicardial or abandoned transvenous leads only when clinical benefit outweighs risk. Conditional recommendation. 2

In‑Scan Requirements

• Continuous ECG monitoring must be maintained throughout the scan. Strong recommendation. 5
• ACLS‑trained personnel (from imaging or device team) must be present. Strong recommendation. 5
• The device team must be immediately available for troubleshooting rhythm disturbances or device‑related issues. Strong recommendation. 4

Post‑Scan Requirements

• Immediate post‑scan device interrogation to verify sensing and pacing performance. Strong recommendation. 4
• Reprogramming to pre‑scan settings must be completed before the patient leaves the MRI suite. Strong recommendation. 1
• Patients with significant parameter changes require intensified follow‑up in the device clinic. Strong recommendation. 4

Field‑Strength Limitations

• For non‑conditional pacemakers, scanning at 3.0 Tesla is not recommended because field strengths > 1.5 Tesla markedly increase the risk of power‑on resets and other safety‑related events. Strong recommendation. 4
• All large prospective safety studies demonstrating low adverse‑event rates were conducted at 1.5 Tesla. Strong recommendation. 1

Evidence Quality

• The 2021 joint statement of the Canadian Cardiovascular Society, Canadian Society for Cardiovascular Magnetic Resonance, and Canadian Heart Rhythm Society provides strong recommendations based on high‑quality evidence, including two large prospective studies (>1,500 patients each) and a meta‑analysis (>5,000 patients). 6

Alternative Imaging Considerations

• When institutional resources cannot support the required monitoring and device‑team availability, alternative modalities such as CT or ultrasound may be considered for shoulder evaluation. However, MRI should not be withheld solely because of a pacemaker if the standardized protocol can be implemented. Conditional recommendation. 6

MRI Safety Protocols for Patients with Pacemakers

MRI‑Conditional Pacemakers

• Modern MRI‑conditional pacemakers may be scanned according to the manufacturer’s specifications, typically up to 3.0 Tesla for most current models (e.g., Medtronic Micra). Strong recommendation based on high‑quality evidence. 7
• The Abbott Nanostim system, although recalled, remains MRI‑conditional only up to 1.5 Tesla. 8

Non‑Conditional (Legacy) Pacemakers

Patients without Pacemaker Dependency

• Scanning at 1.5 Tesla is recommended in a monitored setting with immediate access to the device team. Strong recommendation from the Canadian Cardiovascular Society (CCS) joint statement. 8
• Pre‑scan programming should place the device in a sensing‑only mode (OAO, OVO, or ODO). 8
• After the scan, interrogation and re‑programming to pre‑scan settings are mandatory. 8
• Large prospective studies (> 1,500 patients each) have shown low adverse‑event rates, with only 0.6 % experiencing a transient electrical reset. High‑quality evidence. 8

Patients with Pacemaker Dependency

• Scanning at 1.5 Tesla requires a monitored environment with an ACLS‑trained practitioner and immediate availability of both code and device teams. Strong recommendation. 8, 9
• Pre‑scan programming must switch the device to an asynchronous pacing mode (AOO, VOO, or DOO). 8, 10
• Continuous ECG monitoring throughout the examination is essential. 10
• A meta‑analysis of > 5,000 patients with non‑conditional devices (including 511 dependent patients) demonstrated low adverse‑event rates and no induction of atrial or ventricular arrhythmias. High‑quality evidence. 8

Critical Safety Protocol Requirements

Pre‑Scan Preparation

• Device interrogation to determine pacemaker dependency, sensing thresholds, and pacing thresholds is mandatory. Strong recommendation. 10
• For implantable cardioverter‑defibrillators (ICDs), tachycardia therapies must be disabled to prevent inappropriate shocks. 8
• Patients with unstable intrinsic rhythms require asynchronous pacing programming. 9

During Scan

• ECG monitoring must be maintained throughout the procedure. 10
• ACLS‑trained personnel must be present, affiliated with either the imaging or device team. 9
• Immediate device‑team availability for troubleshooting rhythm disturbances is essential. 9

Post‑Scan Care

• Immediate device interrogation to verify sensing and pacing performance after the MRI. 9
• Re‑programming to pre‑scan settings must be performed before the patient leaves the MRI suite. 8
• Patients who exhibit significant parameter changes require intensified follow‑up in a device clinic. 9

Field‑Strength Limitations

• For non‑conditional devices, 3.0 Tesla scanning is NOT recommended because of an increased risk of safety‑related events, primarily power‑on resets. Strong recommendation. 8, 9
• 1.5 Tesla is the recommended field strength for all non‑conditional pacemakers, supported by high‑quality evidence from multiple large prospective studies. 8

Evidence Base and Guideline Authority

• The 2021 joint statement of the Canadian Cardiovascular Society, the Canadian Society for Cardiovascular Magnetic Resonance, and the Canadian Heart Rhythm Society provides strong recommendations based on high‑quality evidence, including prospective studies demonstrating safety in > 1,500 patients with legacy devices. 8, 7

Common Pitfalls to Avoid

• Never scan non‑conditional devices at 3.0 Tesla – field strengths above 1.5 Tesla markedly increase the risk of device resets. 8
• Never proceed without pre‑scan device interrogation – failure to identify pacemaker dependency can cause life‑threatening bradycardia. 10
• Never forget to disable ICD tachycardia therapies – electromagnetic interference can trigger inappropriate shocks. 8
• Never scan without immediate device‑team availability – unexpected parameter changes may require urgent re‑programming. 9