What is the recommended treatment approach for symptomatic atrial flutter using electrical cardioversion?

Electrical Cardioversion for Atrial Flutter

For symptomatic atrial flutter, synchronized electrical cardioversion is highly effective and should be performed immediately in hemodynamically unstable patients, while elective cardioversion is indicated for stable patients pursuing rhythm control, with atrial flutter requiring lower energy levels than atrial fibrillation for successful conversion. 1

Immediate Cardioversion Indications

Synchronized electrical cardioversion is mandatory for patients with atrial flutter who are hemodynamically unstable and do not respond to pharmacological therapies. 1 This includes patients with:

• Hypotension
• Acute heart failure
• Ongoing chest pain or myocardial ischemia
• Altered mental status 2

Do not delay cardioversion in these patients—proceed without waiting for pharmacological rate control attempts. 1

Elective Cardioversion for Stable Patients

Elective synchronized cardioversion is indicated in stable patients with well-tolerated atrial flutter when pursuing a rhythm-control strategy. 1, 3 This approach is favored to:

• Prevent tachycardia-mediated cardiomyopathy 1
• Address difficult-to-control ventricular rates that are characteristic of atrial flutter 1, 2

Atrial flutter requires significantly lower energy levels for successful cardioversion compared to atrial fibrillation, with success rates approaching 97.9% to 100%. 1, 3, 4

Anticoagulation Requirements

Anticoagulation protocols for atrial flutter must follow identical guidelines as atrial fibrillation—this is non-negotiable. 1, 2

For Flutter ≥48 Hours or Unknown Duration:

• Therapeutic anticoagulation (warfarin INR 2.0-3.0, or DOAC) for at least 3 weeks before and 4 weeks after cardioversion 1, 3
• Alternative: TEE-guided approach with immediate cardioversion if no left atrial thrombus identified, provided anticoagulation is achieved before TEE and maintained for at least 4 weeks after 1

For Flutter <48 Hours:

• High stroke risk patients: IV heparin, LMWH, or direct oral anticoagulant before or immediately after cardioversion, followed by long-term anticoagulation 1
• Low stroke risk patients: IV heparin, LMWH, DOAC, or no antithrombotic may be considered 1

The annual stroke risk in atrial flutter is 3%, making anticoagulation essential. 2

Technical Approach

Use anteroposterior (AP) biphasic truncated exponential waveform (BTE) with maximum energy and patches for optimal success. 4 This configuration:

• Provides superior efficacy compared to anteroapical positioning 4
• Delivers higher current density to atrial tissue 1
• Achieves better outcomes than rectilinear biphasic waveforms 4

Start with 50-100 joules for atrial flutter, as lower energies are typically sufficient compared to atrial fibrillation. 1, 2

Alternative: Rapid Atrial Pacing

Rapid atrial pacing is useful for acute conversion in patients who have pacing wires already in place (permanent pacemaker, ICD, or temporary post-cardiac surgery wires), with success rates exceeding 50%. 1, 3

Technique:

• Pace the atrium at 5-10% above the flutter rate to achieve entrainment 1
• Maintain pacing for ≥15 seconds 1
• Repeat at incrementally faster rates (reducing cycle length by 5-10 ms) until sinus rhythm or atrial fibrillation occurs 1

This approach is particularly valuable when sedation is contraindicated or in digitalis toxicity where DC cardioversion is contraindicated. 1, 3

Critical Pitfalls to Avoid

Never use digoxin, nondihydropyridine calcium channel blockers, or amiodarone in patients with pre-excitation and atrial flutter—these can facilitate rapid AV conduction and cause ventricular fibrillation. 1

Do not perform electrical cardioversion in patients with digitalis toxicity or hypokalemia—correct these conditions first. 1

Recognize that 22-50% of patients develop atrial fibrillation within 14-30 months after successful cardioversion or catheter ablation of atrial flutter. 2, 3 Risk factors include:

• Prior atrial fibrillation
• Depressed left ventricular function
• Structural heart disease
• Increased left atrial size 2, 3

Long-Term Consideration

While electrical cardioversion is highly effective acutely, catheter ablation of the cavotricuspid isthmus should be strongly considered as definitive first-line therapy, with success rates exceeding 90%. 2, 3 This is particularly important for patients with recurrent symptomatic flutter or those refractory to pharmacological rate control.