What are the recommendations for performing a pacemaker (permanent artificial cardiac pacemaker) ECG with a magnet?

Pacemaker ECG with Magnet: Recommendations and Procedures

For pacemaker assessment, applying a magnet over the device generator will force asynchronous pacing at a manufacturer-specific rate, which is essential for evaluating capture and battery status, but this should only be done after confirming the specific device's magnet response. 1

Understanding Magnet Effects on Pacemakers

Basic Principles

• Magnet application causes most bradycardia pacemakers to switch to asynchronous pacing (VOO or DOO mode) at a predetermined rate
• The specific magnet-induced pacing rate varies by manufacturer and battery status:
  • Normal battery: 85-100 bpm (typical range)
  • Decreasing rates indicate battery depletion 1

Important Considerations

• Some pacemaker models have programmable magnet responses or may have this feature disabled 1
• Some devices only force asynchronous pacing for 10 beats before reverting to programmed settings 1
• Always confirm the specific device's magnet response before relying on it for clinical decisions 1, 2

Proper Technique for Magnet Application

1. Identify the device type and manufacturer before applying a magnet 1
2. Position the magnet directly over the pulse generator (not over the leads)
3. Secure the magnet with adhesive tape if continuous asynchronous pacing is needed 1
4. Monitor the ECG continuously during magnet application to:
   • Confirm effective capture in appropriate chamber(s)
   • Assess magnet-induced pacing rate
   • Compare current magnet rate with previous values to detect changes 1

Clinical Goals of Magnet ECG Assessment

Without Magnet (Baseline Assessment)

• Determine if patient displays intrinsic rhythm or is being paced
• Characterize underlying atrial mechanism (sinus rhythm, atrial fibrillation, etc.)
• Verify appropriate sensing in relevant chambers 1

During Magnet Application

• Verify effective capture in appropriate chamber(s)
• Assess magnet rate and compare to previous values
• Evaluate pulse width if it's an elective replacement indicator
• Assess threshold margin test results if available and programmed "on"
• Note any changes in AV interval during magnet application (for dual-chamber devices) 1

Special Considerations

Implantable Cardioverter Defibrillators (ICDs)

• Magnet application to an ICD will NOT force asynchronous pacing
• Magnet will only disable the antitachycardia (shocking) function 1
• Some ICD models temporarily suspend shocking function while magnet is in place
• Other models will turn the therapy off completely and require reprogramming 1
• For pacemaker-dependent ICD patients, the device must be programmed to an asynchronous mode (VOO or DOO) 1

Cardiac Resynchronization Therapy (CRT) Devices

• Consider consulting a CIED team for CRT devices as they have more complex programming 1

Leadless Pacemakers

• A magnet will NOT force asynchronous pacing in leadless pacemakers 1

Subcutaneous ICDs

• A properly positioned magnet will emit an R-wave synchronous beep
• If tone is not audible, reprogramming is necessary 1

Common Pitfalls and Caveats

• Failure to identify device type: Always determine the type of CIED, manufacturer, and model before applying a magnet 2
• Inadequate ECG monitoring: Continuous ECG monitoring is essential during magnet application 1
• Relying solely on magnet response: A full device interrogation may be needed if abnormalities are detected 3
• Electromagnetic interference: Can affect ECG interpretation during magnet testing 1
• Obesity or patient positioning: May prevent effective magnet placement in some patients 1
• Misinterpretation of magnet response: Different devices have different responses to magnet application 2

Documentation Requirements

• Record ECG strips showing:
  • Baseline rhythm before magnet application
  • Response during magnet application
  • Return to baseline after magnet removal
• Compare current magnet rate with previous values
• Document any abnormalities in capture or sensing 1

For most routine post-implant assessments, a properly performed magnet check with ECG monitoring may be sufficient without requiring full programmer interrogation 3, but any abnormalities detected during magnet testing should prompt a complete device interrogation.