Can a patient with a pacemaker undergo synchronized cardioversion for atrial flutter?

Cardioversion for Atrial Flutter in Patients with Pacemakers

Yes, you can safely cardiovert atrial flutter in a patient with a pacemaker when appropriate precautions are taken, including anterior-posterior paddle positioning, device interrogation before and after the procedure, and ensuring backup pacing capability is immediately available. 1, 2

Safety and Feasibility

Cardioversion of atrial flutter is safe in patients with implanted pacemakers when proper protocols are followed. 1 Pacemaker generators are designed with protective circuits against external electrical discharges, though programmed data may be altered by current surges and electricity conducted along implanted electrodes can cause endocardial injury. 1

Contemporary evidence from 763 cardioversion procedures in 372 patients with cardiac implantable devices demonstrated that external cardioversion is safe in the majority of patients, with only two cases of device programming changes and four cases of premature battery depletion observed. 3 No patients died from cardioversion-related device dysfunction within 12 months. 3

Mandatory Pre-Procedure Steps

Before performing cardioversion, you must:

• Interrogate the pacemaker to document baseline function, programming parameters, and pacing thresholds. 1, 2 This establishes a baseline for comparison after the procedure.

• Identify whether the patient is pacemaker-dependent. 2 This determines the level of precaution needed and backup support required.

• Ensure external pacing capability is immediately available for pacemaker-dependent patients. 2

Critical Technical Requirements

Paddle Positioning

Position paddles in the anterior-posterior configuration with paddles as far as possible from the pacemaker generator. 1, 2 This is the single most important technical consideration to reduce risk of device damage and exit block. 2

• Never use the anterior-apex paddle configuration when a pacemaker is present. 2 The risk of exit block is greatest when one paddle is positioned near the impulse generator and the other over the cardiac apex. 1

• Bipolar electrode systems carry lower risk than unipolar systems. 2

Energy Selection for Atrial Flutter

Start with low energy for atrial flutter, typically 50-100 joules. 4 Atrial flutter requires significantly lower energy levels than atrial fibrillation, with success rates approaching 97.9% to 100%. 4

• For biphasic waveforms, consider starting at 200 J to reduce the total number of shocks needed, though this is higher than necessary for most atrial flutter cases. 1, 2

• The median successful energy level is 100 J with biphasic waveform compared to 200 J with monophasic waveform. 1

Mandatory Post-Procedure Steps

Immediately interrogate the pacemaker after cardioversion to detect any alterations in programmed parameters or threshold changes. 1, 2 This is crucial because:

• Programmed data may be altered by current surges 1
• Temporary or permanent increases in stimulation threshold can occur, resulting in loss of ventricular capture 1
• Minor changes in impedances, sensing, and pacing thresholds have been documented 3

Reprogram the device if necessary based on post-cardioversion interrogation findings. 1, 2

Monitor continuously after cardioversion until stable pacemaker function is confirmed, especially in pacemaker-dependent patients. 2

Understanding the Risks

The primary mechanisms of pacemaker damage during cardioversion include: 2

• Exit block (most common concern)
• Endocardial injury from conducted electricity
• Device reprogramming or reset
• Complete battery discharge (rare but documented)

Standard Cardioversion Protocol for Atrial Flutter

Beyond pacemaker considerations, follow standard atrial flutter cardioversion protocols:

• Ensure the patient is hemodynamically stable. If unstable (hypotension, acute heart failure, ongoing chest pain/ischemia, altered mental status), proceed with immediate synchronized cardioversion without delay. 4, 5

• Verify appropriate anticoagulation. Atrial flutter requires identical anticoagulation protocols as atrial fibrillation: therapeutic anticoagulation for at least 3 weeks before and 4 weeks after cardioversion for episodes ≥48 hours or unknown duration. 4, 6

• Synchronize the shock with the QRS complex by monitoring the R wave with an appropriately selected ECG lead. 1

• Ensure serum potassium is in the normal range for safe, effective cardioversion. 1

Algorithm for Pacemaker Patients Requiring Cardioversion

1. Identify pacemaker dependence 2
2. Interrogate the device and document baseline parameters 1, 2
3. Position paddles anterior-posterior, maximally distant from generator 1, 2
4. Ensure backup external pacing is immediately available 2
5. Deliver synchronized cardioversion starting with 50-100 J for atrial flutter 4
6. Immediately re-interrogate the device 1, 2
7. Reprogram if needed based on interrogation findings 1, 2
8. Monitor continuously until stable function confirmed 2

Common Pitfalls to Avoid

• Do not position paddles in anterior-apex configuration – this maximizes risk of exit block. 1, 2

• Do not skip post-cardioversion interrogation – clinically important changes in device function may be critical even though rarely observed. 3

• Do not cardiovert patients with digitalis toxicity or hypokalemia – correct these conditions first. 4

• Do not use AV-nodal blocking agents (beta-blockers, calcium-channel blockers, digoxin) if pre-excitation is present – these can facilitate rapid AV conduction and cause ventricular fibrillation. 4, 5