Is cardioversion effective for typical atrial flutter?

Is Cardioversion Effective for Atrial Flutter?

Yes, cardioversion is highly effective for atrial flutter, with external direct current cardioversion achieving success rates of 95-100% and often requiring only low energy levels (5-50 joules). 1

Electrical Cardioversion: The Gold Standard

Synchronized electrical cardioversion is the procedure of choice when rapid termination of atrial flutter is required. 1

Success Rates and Energy Requirements

• External DC cardioversion achieves conversion rates between 95% and 100% for atrial flutter. 1
• Atrial flutter can be successfully cardioverted with significantly lower energy than atrial fibrillation—typically 5 to 50 joules with monophasic waveforms, and even less with biphasic waveforms. 1
• Biphasic waveforms demonstrate superior efficacy (99.1%) compared to monophasic waveforms (92.4%) for atrial fibrillation, though both are comparably effective for atrial flutter (99.2% vs 99.8%). 1
• An initial energy of 200 J or greater is recommended for atrial fibrillation, but atrial flutter often responds to much lower initial energies. 1

Clinical Indications

Immediate synchronized cardioversion is mandatory for hemodynamically unstable patients with atrial flutter who show hypotension, acute heart failure, ongoing myocardial ischemia, or altered mental status. 1, 2, 3

Elective synchronized cardioversion is indicated in stable patients with well-tolerated atrial flutter when pursuing a rhythm-control strategy, particularly to prevent tachycardia-mediated cardiomyopathy. 1, 3

Alternative Cardioversion Methods

Atrial Overdrive Pacing

Rapid atrial pacing achieves successful conversion in more than 50% of cases and is particularly useful in patients who already have pacing wires in place (permanent pacemaker, ICD, or temporary postoperative wires). 1, 3

• The cumulative success rate for atrial overdrive pacing is 82% (range 55-100%). 1
• Pacing technique: Start at 5-10% above the atrial flutter rate for ≥15 seconds; if unsuccessful, increase the rate incrementally (reduce cycle length by 5-10 ms) until sinus rhythm or atrial fibrillation occurs. 1, 3
• Important caveat: Atrial overdrive pacing may induce sustained atrial fibrillation, though this is often more easily rate-controlled and may subsequently revert to sinus rhythm. 1

Pharmacological Cardioversion

Pharmacological cardioversion is considerably less effective than electrical cardioversion for atrial flutter. 4

• Intravenous ibutilide converts approximately 60-70% of acute atrial flutter episodes to sinus rhythm, making it the most effective antiarrhythmic agent for chemical cardioversion. 1, 3
• High-dose (2 mg) ibutilide is significantly more effective than sotalol (1.5 mg/kg) for atrial flutter conversion (70% vs 19%). 1
• Critical safety concern: Ibutilide carries a 1.5-3% risk of torsades de pointes, requiring continuous ECG monitoring during infusion and for at least 4 hours after completion. 1, 3
• Class III agents (dofetilide, ibutilide) are more effective than class I agents (flecainide, propafenone) or sotalol for atrial flutter conversion. 1
• Neither IV AV-nodal blocking agents nor amiodarone are effective for arrhythmia conversion, though they may provide rate control. 1

Critical Clinical Pitfalls

Pre-Excitation Syndromes (Wolff-Parkinson-White)

AV-nodal blocking agents (beta-blockers, calcium-channel blockers, digoxin, adenosine) must never be used in patients with WPW and atrial flutter because they can facilitate rapid antegrade conduction over the accessory pathway, leading to ventricular acceleration, hypotension, or ventricular fibrillation. 3

Class IC Antiarrhythmics

Propafenone or flecainide can slow atrial flutter rate and paradoxically precipitate 1:1 AV conduction, producing dangerously rapid ventricular rates. 1, 3

• Prevention strategy: Always co-administer an AV-nodal blocking drug with class IC agents, or consider catheter ablation of the cavotricuspid isthmus. 1, 3

Rate Control Before Cardioversion

Pretreatment with rate control medication before electrical cardioversion is associated with reduced success rates (adjusted OR 0.39,95% CI 0.21-0.74) and should be avoided. 5

Anticoagulation Requirements

Antithrombotic therapy in atrial flutter must follow the same protocols as atrial fibrillation, as stroke risk averages approximately 3% annually. 1, 3

• For atrial flutter of less than 48 hours' duration in low thromboembolic risk patients, anticoagulation should be initiated before or immediately after cardioversion and continued for at least 4 weeks. 2
• For duration >48 hours or unknown, provide therapeutic anticoagulation for 3 weeks before and 4 weeks after planned cardioversion. 3

Long-Term Outcomes

After a single electrical cardioversion without antiarrhythmic drugs, 42% of patients maintain sinus rhythm long-term. 6

With serial cardioversion and prophylactic antiarrhythmic drugs, 90% of patients can be kept in sinus rhythm for 5 years. 6

Left atrial size is inversely related to the efficacy of single-shock cardioversion (P = 0.025), while long arrhythmia duration and impaired cardiac function predict poor outcomes. 6