Can a patient with a pacemaker (Permanent Artificial Cardiac Pacemaker) undergo cardioversion?

Cardioversion in Patients with Pacemakers

Yes, patients with pacemakers can safely undergo cardioversion when appropriate precautions are taken, though the procedure carries specific risks to the pacemaker system that require protective measures. 1

Key Safety Principle

The fundamental requirement is proper paddle positioning: use anterior-posterior configuration with paddles positioned as far as possible from the pacemaker generator. 1 This single intervention dramatically reduces the risk of device damage and exit block.

Mandatory Pre- and Post-Procedure Steps

• Interrogate the pacemaker before cardioversion to document baseline function and programming 1
• Interrogate again immediately after cardioversion to detect any alterations in programmed parameters or threshold changes 1
• Reprogram the device if necessary based on post-cardioversion interrogation findings 1

These steps are non-negotiable because electrical current can alter programmed data through current surges and may cause endocardial injury at the lead tip. 1

Understanding the Risks

The primary mechanisms of pacemaker damage during cardioversion include:

• Exit block from temporary or permanent increases in stimulation threshold, potentially causing loss of ventricular capture 1, 2
• Endocardial injury at the electrode-myocardial interface from conducted electrical energy 1, 2
• Device reprogramming or reset to backup modes from current surges 1
• Complete battery discharge in rare cases, particularly with improper paddle placement 3

The risk is highest when one paddle is positioned near the pulse generator and the other over the cardiac apex—this configuration should be avoided. 1

Protective Measures During the Procedure

Paddle positioning is the most critical protective factor:

• Use anterior-posterior configuration exclusively 1
• Position paddles as distant as possible from the generator (typically implanted anteriorly) 1
• Never place paddles in the anterior-apex configuration when a pacemaker is present 1

Additional protective considerations:

• Bipolar lead systems carry lower risk than unipolar systems 1
• Have temporary pacing capability immediately available, especially in pacemaker-dependent patients 2, 4
• Consider high-output pacing immediately before cardioversion in dependent patients to ensure consistent capture afterward 2

Special Consideration for Pacemaker-Dependent Patients

For patients who are pacemaker-dependent (no underlying escape rhythm), additional precautions are essential:

• Ensure external pacing capability is immediately available 2, 4
• Consider prophylactic high-output pacing before shock delivery 2
• Monitor continuously after cardioversion until stable pacemaker function is confirmed 5

Pacemaker dependence should be determined by chart review and ECG examination before the procedure. 1

Energy Considerations

• Start with appropriate energy levels (200 J for biphasic waveforms) 1
• Higher initial energy may reduce total number of shocks needed, potentially reducing cumulative device exposure 1
• Low-energy internal cardioversion (when electrodes are positioned in right atrium, coronary sinus, or left pulmonary artery) does not interfere with pacemaker function 1

Common Pitfalls to Avoid

Critical errors that increase risk:

• Failing to interrogate the device before and after cardioversion 1
• Using anterior-apex paddle configuration instead of anterior-posterior 1
• Proceeding without available backup pacing in dependent patients 2, 4
• Positioning paddles near the pulse generator 1, 3

The case reports demonstrate real-world consequences: One patient experienced complete exit block with severe nodal bradycardia after 160 J cardioversion 2, while another had complete battery discharge when the anterior paddle was positioned near the generator 3. Both complications were directly related to suboptimal paddle positioning.

Device-Specific Considerations

• Rate-responsive pacemakers: The rate-adaptive mode should ideally be disabled before cardioversion when possible 6
• Dual-chamber devices: Both atrial and ventricular thresholds may be affected, though ventricular threshold changes are more common 2, 4
• ICDs with pacing capability: Follow the same precautions; the ICD's defibrillation function should be disabled during external cardioversion 6

Bottom Line Algorithm

1. Identify pacemaker dependence (chart review, ECG) 1
2. Interrogate device and document baseline function 1
3. Position paddles anterior-posterior, maximally distant from generator 1
4. Ensure backup pacing available (especially if dependent) 2, 4
5. Deliver cardioversion with appropriate energy 1
6. Immediately re-interrogate device and reprogram if needed 1
7. Monitor continuously until stable function confirmed 5

The evidence from multiple ACC/AHA/ESC guidelines consistently supports that cardioversion is safe in pacemaker patients when these precautions are followed. 1 The key is recognizing that this is not a contraindication but rather a situation requiring specific technical modifications to standard cardioversion technique.