What is the recommended protocol for cardioversion (cardioversion) in patients with arrhythmias?

Cardioversion Protocol for Arrhythmias

Immediate Cardioversion: When to Act Without Delay

Perform immediate synchronized direct-current cardioversion for any patient with hemodynamic instability—defined as acute altered mental status, ongoing myocardial ischemia, symptomatic hypotension, acute heart failure, or shock—regardless of arrhythmia duration or anticoagulation status. 1, 2, 3

Hemodynamic Instability Indicators:

• Systolic blood pressure <90 mmHg or symptomatic hypotension despite adequate support 3
• Acute chest pain suggesting active ischemia 1
• Acute pulmonary edema or decompensated heart failure 1, 2
• Altered mental status or syncope 3
• Pre-excitation syndromes (WPW) with rapid ventricular response 1, 2

Critical Action Points:

• Provide sedation in conscious patients, but never delay cardioversion in critically unstable patients to achieve sedation 3
• For ventricular tachycardia with hemodynamic instability, immediate sedation should be given to conscious patients before cardioversion, but proceed immediately if the patient is unconscious 1
• Start defibrillation at maximum output for cardiac arrest due to ventricular tachyarrhythmias 1

Anticoagulation Protocol: The 48-Hour Rule

For AF/Atrial Flutter <48 Hours Duration:

• Initiate anticoagulation as soon as possible before or immediately after cardioversion 2
• Continue therapeutic anticoagulation for at least 4 weeks post-cardioversion 1, 2, 3

For AF/Atrial Flutter ≥48 Hours or Unknown Duration:

Two acceptable pathways exist: 1, 2, 3

1. Conventional approach: Therapeutic anticoagulation for 3 weeks pre-cardioversion, then proceed with cardioversion, followed by 4 weeks post-cardioversion anticoagulation 1, 2, 3

2. TEE-guided approach: Perform transesophageal echocardiography to exclude left atrial thrombus, then proceed with cardioversion if no thrombus is present, with therapeutic anticoagulation initiated immediately and continued for 4 weeks 1, 2

Emergency Exception:

• If hemodynamic instability requires immediate cardioversion despite ≥48 hours duration, administer IV heparin bolus followed by continuous infusion, then transition to oral anticoagulation for at least 4 weeks post-procedure 2, 3

Critical pitfall: Patients with cardiac amyloidosis have a 31% incidence of intracardiac thrombus even with adequate anticoagulation ≥3 weeks, requiring heightened vigilance 4

Electrical Cardioversion Technique

Equipment and Energy Selection:

For persistent atrial fibrillation, use anteroposterior (AP) biphasic truncated exponential waveform (BTE) with maximum energy and patches as the optimal strategy (RR 1.35 vs. incremental energy, 95% CI 1.17-1.55). 5

• Always use synchronized mode to deliver shock during the R wave, avoiding the vulnerable period of the cardiac cycle 2, 3
• Position defibrillator patches/paddles at least 8 cm from ICD generator if present 1, 3
• Active compression during shock delivery with AP BTE incremental energy improves success (RR 1.14,95% CI 1.00-1.31) 5

If Initial Cardioversion Fails:

• Adjust electrode position 2
• Apply firm pressure over electrodes 2
• Administer antiarrhythmic medication (see below) and repeat cardioversion 2

Success Rates by Arrhythmia Type:

• Atrial flutter: 97.9-100% success with electrical cardioversion 5
• Paroxysmal AF: 98% success rate in emergency settings 6
• Persistent AF: Variable based on technique, highest with AP BTE maximum energy 5

Pharmacological Cardioversion Options

For Atrial Fibrillation Without Structural Heart Disease:

Use flecainide or propafenone IV as first-line agents for recent-onset AF in patients without structural heart disease (excluding severe LV hypertrophy, heart failure with reduced ejection fraction, or coronary artery disease). 2

• Flecainide: 200-300 mg oral (RR 2.17 vs. placebo, 95% CI 1.68-2.79) 1, 5
• Propafenone: 600 mg oral (RR 1.98 vs. placebo, 95% CI 1.67-2.34) 1, 5
• "Pill-in-the-pocket" approach: Single oral bolus of propafenone or flecainide can be administered outside hospital once safety is established, but must pretreat with beta-blocker or non-dihydropyridine calcium channel blocker to prevent rapid AV conduction if atrial flutter develops 1

For Atrial Fibrillation With Structural Heart Disease:

Use amiodarone IV for patients with structural heart disease (severe LV hypertrophy, heart failure with reduced ejection fraction, or coronary artery disease). 2

• Amiodarone: 300 mg IV over 1 hour, followed by 10-50 mg/h continuous infusion (RR 1.69 vs. placebo, 95% CI 1.42-2.02) 1, 7, 5
• Amiodarone provides both rate control and rhythm stabilization with minimal negative inotropic effects 7
• Can be administered outpatient when rapid restoration is not necessary 1

For Atrial Flutter:

Ibutilide is the most effective pharmacological agent for atrial flutter (RR 21.45 vs. placebo, 95% CI 4.41-104.37). 5

• Ibutilide: 1 mg IV over 10 minutes; repeat 1 mg if necessary 1, 8, 5
• Critical warning: Monitor for QT prolongation and torsades de pointes; have defibrillator immediately available 1, 8
• Alternative agents: Propafenone (RR 7.15), dofetilide (RR 6.43), or sotalol (RR 6.39) 5

For Ventricular Tachycardia (Hemodynamically Stable):

• Procainamide or flecainide IV for patients without severe heart failure or acute MI 1
• Amiodarone IV for patients with heart failure or suspected ischemia 1
• Verapamil or beta-blockers for LV fascicular VT (RBBB morphology with left axis deviation) 1
• Lidocaine is only moderately effective and should not be first-line 1

Enhancing Cardioversion Success and Preventing Recurrence

Pretreat with antiarrhythmic drugs to enhance direct-current cardioversion success and prevent early AF recurrence: 1, 2, 3

• Amiodarone (Class IIa, Level B) 1, 2
• Flecainide (Class IIa, Level B) 1
• Ibutilide (Class IIa, Level B) 1
• Propafenone (Class IIa, Level B) 1
• Sotalol (Class IIa, Level B) 1

For patients who relapse to AF after successful cardioversion, repeat the procedure following prophylactic administration of antiarrhythmic medication 1

Absolute Contraindications

Never perform electrical cardioversion in the following situations: 1, 3

1. Digitalis toxicity (Class III, Level C) 1, 3
2. Hypokalemia (Class III, Level C) 1, 3

Drugs to Avoid:

• Digoxin and sotalol are harmful when used for pharmacological cardioversion of AF 1
• Never use IV amiodarone, adenosine, digoxin, or non-dihydropyridine calcium channel blockers in pre-excited AF (WPW); instead use IV procainamide or ibutilide 3
• Never use verapamil for wide-complex tachycardias unless proven supraventricular origin (Class III, Level B) 3

Special Populations and Considerations

Post-PCI Patients with Persistent AF:

• Amiodarone is the preferred agent due to effective rate control without significant negative inotropic effects in patients with borderline blood pressure 7
• Beta-blockers and calcium channel blockers should be used with extreme caution in patients with borderline blood pressure (e.g., 100/90 mmHg) due to risk of precipitating hypotension 7

Cardiac Amyloidosis:

• Cardioversion cancellation rate is 28% (vs. 7% in controls) mainly due to intracardiac thrombus 4
• Procedural complications occur in 14% (vs. 2% in controls), including ventricular arrhythmias and severe bradyarrhythmias requiring pacemaker 4
• Success rate remains high (90%) when cardioversion is performed 4

Acute Coronary Syndrome:

• Urgent cardioversion is recommended for new-onset AF with hemodynamic compromise, ongoing ischemia, or inadequate rate control 2

Critical Pitfalls to Avoid

1. Never delay cardioversion in hemodynamically unstable patients to obtain anticoagulation when AF duration is uncertain but instability is present 2, 3

2. Never repeat cardioversion frequently in patients who have relatively short periods of sinus rhythm between relapses despite prophylactic antiarrhythmic therapy (Class III, Level C) 1

3. Always rule out pre-excitation (WPW) immediately before administering AV nodal blocking agents, as these are contraindicated and immediate cardioversion is required 3, 7

4. Ensure adequate sedation in conscious patients to minimize discomfort and patient movement during shock delivery 3

5. Monitor for at least 24 hours post-cardioversion for arrhythmia recurrence and complications 9, 6