What are the indications, pre‑procedure preparation, procedural steps, and post‑procedure management for direct current cardioversion (synchronized electrical shock) in patients with atrial fibrillation or atrial flutter?

Direct Current Cardioversion (DCCV) for Atrial Fibrillation and Atrial Flutter

Indications for DCCV

Immediate R-wave synchronized direct-current cardioversion is mandatory for hemodynamically unstable patients with atrial fibrillation or atrial flutter, including those with ongoing myocardial ischemia, symptomatic hypotension, angina, or heart failure when rapid ventricular response does not respond promptly to pharmacological measures. 1, 2, 3

Class I Indications (Must Perform):

• Hemodynamic instability: Ongoing myocardial ischemia, symptomatic hypotension, angina, or heart failure with rapid ventricular response unresponsive to medications 1, 2
• Pre-excitation syndromes (WPW): Very rapid tachycardia or hemodynamic instability in AF with pre-excitation 1, 3
• Symptomatic patients: When AF symptoms are unacceptable to the patient, even without hemodynamic compromise 1, 3

Class IIa Indications (Reasonable to Perform):

• Long-term rhythm control strategy as part of ongoing AF management 1
• Patient preference for infrequently repeated cardioversions for symptomatic or recurrent AF 1

Class III (Do Not Perform):

• Digitalis toxicity or hypokalemia - absolute contraindications 1, 2, 3
• Frequent repetition in patients with short sinus rhythm periods between relapses despite prophylactic antiarrhythmic therapy 1, 3

Pre-Procedure Preparation

Anticoagulation Requirements

For AF duration ≥48 hours or unknown duration, therapeutic anticoagulation for at least 3 weeks before cardioversion is mandatory, with continuation for at least 4 weeks post-procedure. 2, 3, 4

AF Duration <48 Hours:

• Initiate anticoagulation as soon as possible before or immediately after cardioversion 2
• Continue anticoagulation for at least 4 weeks post-cardioversion 2

AF Duration ≥48 Hours or Unknown Duration:

• Option 1: Therapeutic anticoagulation for 3 weeks pre-cardioversion, then proceed 2, 3, 4
• Option 2: Transesophageal echocardiography (TEE) to exclude left atrial thrombus, then proceed with 48 hours of heparin anticoagulation 2, 3, 4
• Direct oral anticoagulants (DOACs) are preferred over vitamin K antagonists 3

Emergency Cardioversion:

• Proceed immediately with cardioversion 2
• Administer IV heparin bolus followed by continuous infusion 2
• Continue oral anticoagulation for at least 4 weeks post-procedure 2

Patient Preparation

• Fasting state required for adequate anesthesia 1
• Effective anesthesia (not merely sedation) using short-acting agents like IV midazolam and/or propofol to achieve amnesia and avoid pain 3, 4
• Correct electrolyte abnormalities, particularly hypokalemia 1
• Ensure patient is not in digitalis toxicity 1

Pre-Procedure Imaging

• TEE should be performed to exclude left atrial appendage thrombus if using the TEE-guided approach 2, 3
• TEE is mandatory in patients with left atrial appendage occlusion devices 5

Procedural Steps

Technical Setup

Use R-wave synchronized mode to deliver shock during the R wave, avoiding the vulnerable period of the cardiac cycle to prevent ventricular fibrillation. 1, 3

Equipment Configuration:

• Biphasic waveform defibrillators are more effective than monophasic devices 3, 6
• Electrode size: 8-12 cm diameter paddles or self-adhesive pads 3, 4
• Electrode position: Anteroposterior or apex-anterior positions are equally effective 4
• Use electrolyte-impregnated pads to minimize electrical resistance 1
• Apply firm pressure with hand-held paddles to reduce transthoracic impedance 4

Energy Levels:

• Atrial fibrillation: Start at 150-200J with biphasic waveforms (or 100J with monophasic) 1, 3, 4
• Atrial flutter: Start at 50J (generally requires lower energy) 4
• Increase energy for subsequent shocks if initial attempt fails 3

Monitoring During Procedure

• Select ECG lead that clearly displays both R wave and atrial activation 1
• Ensure proper QRS synchronization before each shock 3, 6
• Deliver shocks during expiration or chest compression for higher energy delivery to the heart 1

If Initial Cardioversion Fails

Adjust electrode position, apply pressure over electrodes, or administer antiarrhythmic medication as pretreatment before repeating cardioversion attempts. 7, 2

Strategies to Enhance Success:

• Reposition electrodes 7, 2
• Apply increased pressure over electrodes 7, 2
• Pretreatment with antiarrhythmic drugs (Class IIa recommendation): amiodarone, flecainide, ibutilide, propafenone, or sotalol 7, 2
• Higher energy cardioversion (up to 720J using two defibrillators) may be considered in refractory cases, particularly in obese patients 8

Post-Procedure Management

Immediate Post-Cardioversion Care

• Monitor for post-cardioversion bradycardia 3
• Assess for skin burns at electrode sites 3
• Monitor for thromboembolic complications (highest risk within first few days) 3

Anticoagulation Continuation

Continue anticoagulation for at least 4 weeks after successful cardioversion, with long-term anticoagulation based on CHA₂DS₂-VASc score regardless of rhythm outcome. 2, 3

• Long-term anticoagulation decision is independent of whether sinus rhythm is maintained 2, 3
• In patients with left atrial appendage occlusion devices, 22% may require new oral anticoagulation post-DCCV 5

Antiarrhythmic Therapy

Antiarrhythmic drugs should be considered to maintain sinus rhythm after cardioversion, with selection based on underlying cardiac structure. 7, 2, 3

For Patients WITHOUT Structural Heart Disease:

• Flecainide or propafenone as first-line agents 2
• Exclude patients with severe left ventricular hypertrophy, heart failure with reduced ejection fraction, or coronary artery disease 2

For Patients WITH Structural Heart Disease:

• Amiodarone is preferred 2
• Alternative options: dronedarone or sotalol based on patient characteristics 3

Monitoring for Complications

• Monitor patients receiving QT-prolonging drugs (dofetilide, sotalol) in hospital for 24-48 hours to evaluate for torsades de pointes 7
• Assess for pulmonary edema (occurs in 1-3% of patients, particularly those with coexistent heart disease) 9
• No overnight hospitalization is typically required for uncomplicated cases 1

Management of Early Relapse

Repeated direct-current cardioversion attempts may be made following administration of antiarrhythmic medication if early relapse occurs. 1, 7

• Pretreatment with antiarrhythmic medication enhances success and prevents recurrent AF 7
• However, avoid frequent repetition in patients with short sinus rhythm periods between relapses despite prophylactic therapy 1

Common Pitfalls and Caveats

Critical Safety Issues:

• Never perform cardioversion in digitalis toxicity or hypokalemia - this can precipitate life-threatening arrhythmias 1, 2
• Never use asynchronous shocks for AF/flutter - this risks inducing ventricular fibrillation 1
• Never omit anticoagulation in AF ≥48 hours or unknown duration without TEE guidance 2, 3

Special Populations:

• Pre-excited AF (WPW): Never use IV amiodarone, adenosine, digoxin, or nondihydropyridine calcium channel blockers; use IV procainamide or ibutilide instead 2
• Obese patients: May require higher energy levels or alternative electrode positioning 8
• Patients with left atrial appendage occlusion devices: TEE is mandatory pre-procedure to assess device position and exclude thrombus 5

Avoiding Unnecessary Procedures:

• Do not perform frequent repeated cardioversions in patients who consistently relapse to AF despite antiarrhythmic therapy - consider alternative strategies like AV nodal ablation with permanent pacing or surgical ablation 7