If a female patient has a pacemaker, can she safely undergo MRI of the shoulder, or should alternative imaging such as CT or ultrasound be used?

MRI Safety in Patients with Pacemakers

A female patient with a pacemaker can safely undergo MRI of the shoulder at 1.5 Tesla following a standardized protocol that includes pre-scan device interrogation, appropriate device programming, continuous monitoring during the scan, and post-scan device reprogramming—this applies to both MRI-conditional and non-conditional pacemakers. 1

Device Type Determines Specific Protocol

MRI-Conditional Pacemakers

For modern MRI-conditional pacemakers, scanning should be performed at 1.5 Tesla when possible, with the device programmed to MRI-compatible mode. 1

• Most current MRI-conditional devices are approved up to 3.0 Tesla (e.g., Medtronic Micra), though 1.5 Tesla is preferred when available 2
• The device team must perform pre-scan interrogation to evaluate underlying rhythm, screen for recent arrhythmias, ensure stable sensing, and program the device to MRI-compatible mode 1
• Some newer systems have auto-detection features that automatically trigger safe mode in the MRI environment, but post-scan interrogation remains mandatory 1
• Post-scan reprogramming to pre-scan settings is required to ensure lead integrity and return to normal pacing parameters 1

Non-Conditional (Legacy) Pacemakers

For non-conditional pacemakers, MRI at 1.5 Tesla is safe when performed with a rigorous protocol—large prospective studies of over 1,500 patients each demonstrated low adverse event rates with only 0.6% experiencing transient electrical reset. 1

For Patients WITHOUT Pacemaker Dependency:

• Program the device to sensing-only mode (OAO, OVO, or ODO) before scanning 2
• Perform the scan in a monitored setting with immediate access to the device team 2
• A meta-analysis of over 5,000 patients with non-conditional devices showed low adverse event rates with no induction of atrial or ventricular arrhythmias 1

For Patients WITH Pacemaker Dependency:

• Program the device to asynchronous pacing mode (AOO, VOO, or DOO) before scanning 1, 2
• Require continuous ECG monitoring throughout the examination 2
• An ACLS-trained healthcare practitioner must be present and supervise the scan 1, 2
• Both code team and device team must be immediately available 1, 2
• A meta-analysis including 511 pacemaker-dependent patients demonstrated safety with this protocol 1

Mandatory Protocol Components

Pre-Scan Requirements:

• Device interrogation to determine pacemaker dependency, sensing thresholds, and pacing thresholds is mandatory 1, 2
• Review all available medical information including chest radiography to identify lead extenders, retained epicardial leads, abandoned transvenous leads, or fractured leads 1
• Patients with lead extenders or fractured leads should not undergo MRI 1
• MRI may be considered in patients with epicardial or abandoned transvenous leads when clinical need strongly outweighs potential risks 1

During Scan:

• Continuous ECG monitoring must be maintained 1, 2
• ACLS-trained personnel affiliated with either the imaging or device team must be present 1, 2
• Device team must be immediately available for troubleshooting rhythm disturbances or device-related concerns 1, 2

Post-Scan Requirements:

• Immediate device interrogation to verify sensing and pacing performance after MRI 1, 2
• Reprogramming to pre-scan settings must be performed before the patient leaves the MRI suite 1, 2
• Patients with significant parameter changes require intensified follow-up in the device clinic 1, 2

Critical Field Strength Limitation

For non-conditional pacemakers, scanning at 3.0 Tesla is NOT recommended—field strengths above 1.5 Tesla significantly increase the risk of power-on resets and other safety-related events. 1, 2

• A meta-analysis identified field strength >1.5 Tesla as a risk factor for safety-related events in patients with non-conditional devices 1
• All large prospective safety studies demonstrating low adverse event rates were conducted at 1.5 Tesla 1, 3

Evidence Quality

The 2021 Canadian Cardiovascular Society/Canadian Society for Cardiovascular Magnetic Resonance/Canadian Heart Rhythm Society joint statement provides strong recommendations based on high-quality evidence, including two large prospective studies with over 1,500 patients each and a meta-analysis of over 5,000 patients 1. The MagnaSafe registry, which included 1,000 pacemaker cases, reported no deaths, lead failures, losses of capture, or ventricular arrhythmias when the standardized protocol was followed 3.

Common Pitfalls to Avoid

• Never scan non-conditional devices at 3.0 Tesla—this markedly increases the risk of device resets 1, 2
• Never proceed without pre-scan device interrogation—failure to identify pacemaker dependency can cause life-threatening bradycardia 1, 2
• Never scan pacemaker-dependent patients without programming to asynchronous mode—sensing mode can result in inappropriate pacing inhibition 1, 2
• Never scan patients with lead extenders or fractured leads—these are absolute contraindications 1
• Never allow the patient to leave without post-scan interrogation and reprogramming—device parameters may have changed during the scan 1, 2

Alternative Imaging Consideration

While MRI is safe with appropriate protocols, if institutional resources do not permit the required monitoring and device team availability, alternative imaging modalities (CT or ultrasound) should be considered for shoulder evaluation. However, MRI should not be withheld solely due to pacemaker presence when proper protocols can be implemented, as the evidence demonstrates safety with standardized management. 1, 3