Which patients with recent-onset atrial fibrillation/flutter can be cardioverted in the ED?
Bottom line up top: Patients meeting any of the following criteria can be safely cardioverted in the emergency department:
1. Patients on anticoagulation for more than 3 weeks, regardless of time of onset.
2. Low-risk patients (by CHA₂DS₂-VASc or CHADS-65) with onset ≤ 48 hours.
3. High-risk patients (by CHA₂DS₂-VASc or CHADS-65) with onset ≤ 12 hours.
Clinical scenario
A 72-year-old woman with hypertension and paroxysmal atrial fibrillation presents with palpitations that began 4 hours ago. Vitals: HR 143, BP 142/83, SpO₂ 99% on room air. ECG shows a rapid, irregularly irregular rhythm with no ST changes. Her only medication is amlodipine. About 15 years ago she had a similar episode, was admitted, and was electrically cardioverted after a couple of days, with no recurrence since. Her cardiologist told her to come to the ED to be admitted for cardioversion, but she asks whether she really needs to be admitted.
What your gut says: Rate control, admit to cardiology, and let them take it from there.
What the evidence says
Atrial fibrillation/flutter (AF) is one of the most common dysrhythmias in emergency practice. Over time it promotes clot formation and stroke, and can lead to cardiac remodeling and heart failure.
Many patients have AF with rapid ventricular response secondary to an underlying process (sepsis, pulmonary embolism, severe hyperthyroidism, and so on). Treat the cause in these patients.
A substantial group presents with recent-onset "lone" AF. For these patients, the goal is to restore sinus rhythm.
The standard approach versus ED cardioversion
Standard: transesophageal echo (TEE) to look for clot in the left atrium and appendage, then either cardiovert if no clot is seen, or anticoagulate and defer cardioversion. This usually requires admission, although expedited outpatient follow-up is reasonable if the system allows it.
Alternative: ED cardioversion without TEE in appropriately selected patients. Numerous studies have shown this is safe (Michael 1999; Stiell 2010; Scheuermeyer 2010; Coll-Vinent 2013).
Who qualifies?
Patients currently on appropriate anticoagulation, regardless of time of onset.
Low-risk patients with onset less than 48 hours before presentation.
High-risk patients with onset less than 12 hours before presentation.
Determine risk with a validated score such as CHA₂DS₂-VASc or CHADS-65. Low risk is a score < 2 in men and < 3 in women.
Time of onset is critical. Consider ED cardioversion only when symptom onset is clear. A vague sense of feeling unwell or weak is not adequate.
How: the Ottawa Aggressive Protocol
The Ottawa Aggressive Protocol (Stiell 2010) provides a structured approach.
Step 1: Chemical cardioversion with procainamide
Procainamide 18–20 mg/kg, infused over 30–45 minutes.
Success rates may be as low as 58%.
Adverse effects: hypotension (attributed to the diluent), QRS widening, and QTc prolongation. Stop the infusion if either interval increases by more than 50%.
Its main advantage is speed: if it is going to work, it usually works during the infusion or soon after.
Amiodarone is often suggested, but its success rate is also only 50–60%, and its effect is delayed. Studies show benefit over placebo only after 6–8 hours (Chevalier 2003).
Step 2: Electrical cardioversion
If procainamide fails (or has failed for this patient before), move to electrical cardioversion.
Success rate is 91–97%, and with synchronization it has fewer side effects than any available drug.
Place pads in the anterior-lateral position.
Start at maximal energy (biphasic 200 J) to maximize first-shock success (Glover 2008; Schmidt 2021).
After cardioversion: anticoagulation
Consider a direct oral anticoagulant (DOAC) based on thromboembolic risk.
The AHA guideline recommends anticoagulation for all patients with thromboembolic risk > 2% per year (AHA 2023). This corresponds to a CHA₂DS₂-VASc score ≥ 2 in men and ≥ 3 in women.
Many cardiologists prefer to anticoagulate everyone after cardioversion, at least in the short term, regardless of risk.
Clinical bottom line
ED cardioversion is safe and effective for a subset of patients: those with clear symptom onset or on long-term anticoagulation. The Ottawa Aggressive Protocol can be used to cardiovert these patients and limit admissions.
Clinical pearls
Pin down the time of onset. It is the most important question.
Exclude a secondary cause (sepsis, PE, thyrotoxicosis) before attempting rhythm control.
Go big on the first shock: 200 J biphasic, synchronized.
Arrange anticoagulation and follow-up before discharge.
Resources
EM:RAP: Atrial fibrillation update
Core EM: The Ottawa Aggressive Protocol
Atzema CL, Barrett TW. Managing atrial fibrillation. Ann Emerg Med. 2015;65(5):532–539. PMID: 25701296
Which Patients with Recent-Onset AF/Flutter Can I Cardiovert? (PDF)
References
Chevalier P, et al. Amiodarone versus placebo and class Ic drugs for cardioversion of recent-onset atrial fibrillation: a meta-analysis. J Am Coll Cardiol. 2003;41:255–262. PMID: 12535819
Glover BM, et al. Biphasic energy selection for transthoracic cardioversion of atrial fibrillation: the BEST AF trial. Heart. 2008;94:884–887. PMID: 17591649
Scheuermeyer FX, et al. Thirty-day outcomes of emergency department patients undergoing electrical cardioversion for atrial fibrillation or flutter. Acad Emerg Med. 2010;17:408–415. PMID: 20370780
Schmidt AS, et al. Anterior-lateral versus anterior-posterior electrode position for cardioverting atrial fibrillation. Circulation. 2021. PMID: 34814700
Stiell IG, et al. Association of the Ottawa Aggressive Protocol with rapid discharge of emergency department patients with recent-onset atrial fibrillation or flutter. CJEM. 2010;12(3):181–191. PMID: 20522282
