Cardioversion and discharge of recent onset AF is pretty much the accepted treatment in almost every country in the world with the exception of the United States.
Nine years ago, a 55-year-old male presented to the ED with an irregular heart rate of approximately 167 bpm for 4 hours. Recommendations were made for a diltiazem bolus and infusion with admission to the hospital. The patient, being a rather obnoxious individual, refused the therapy and insisted on electrical cardioversion. After an exasperating period of arguing, the ED relented and cardioverted the patient to preserve the sanity of the nursing staff. The patient was successfully converted to normal sinus rhythm and discharged. Realizing that they had not killed the director of the department by the cardioversion, the ED expanded this approach to all patients with recent onset atrial fibrillation and flutter.
Since that initial case, the ED has successfully cardioverted and discharged over 500 cases of recent onset atrial fibrillation/flutter (AF). Cardioversion and discharge of recent onset AF is pretty much the accepted treatment in almost every country in the world with the exception of the United States. The approach has certainly been shown to be safe with virtually no publications documenting major adverse events following ED cardioversions. [1-4] It is effective, with electrical cardioversion being the most efficient means to restore normal sinus rhythm, followed by chemical cardioversion with procainamide.
There is a downstream benefit to ED cardioversion stemming from the fact that the longer the heart remains in atrial fibrillation, the more the atrium becomes conditioned to accept this rhythm. As the electrophysiologists phrase it, a-fib begets a-fib. The sooner a patient is converted out of this rhythm, the greater the likelihood they will be able to maintain normal sinus rhythm.  Finally, ED cardioversion and discharge is dramatically more cost effective compared with management approaches requiring hospital admission or observation. 
WHY ARE AMERICAN EMERGENCY PHYSICIANS SO AVERSE TO THIS MANAGEMENT APPROACH?
Emergency department cardioversion and discharge is not without some controversies. The exact definition of “recent onset” is debatable, with the maximum acceptable duration of symptoms prior to conversion varying between 48 and 72 hours. There is also the issue of when exactly did the arrhythmia begin. Most practitioners who support ED cardioversion will only attempt the procedure in patients who can clearly describe an exact onset time for the arrhythmia, although there are a few exceptions.
Implanted devices that can track the patient’s heart rhythm may be interrogated to determine the precise onset time and nature of the rhythm change. While activity trackers can identify a time when a patient’s tachycardia began, they cannot distinguish the specific rhythm.  The other exception to a firm onset time may be patients known to normally reside in NSR who are reliably on anticoagulants and present with new cardio respiratory symptoms and a rhythm change to atrial fibrillation or flutter.
Probably the number one reason for emergency physician’s avoiding cardioversion of atrial fibrillation / flutter is fear of embolization of an atrial clot. Prolonged periods of AF can result in sludging of blood in the atria and formation of blood clots in the left atrial appendage. The argument is made that a patient’s recollections of the onset time for their arrhythmia may not be accurate, and the duration of the AF may be greater than 48-72 hours. In addition, extended monitoring of patients has revealed that many of these patients can flip into and out of AF without the patient’s sensing the rhythm changes.
These concerns have led to the belief that all patients require a transesophegeal echocardiogram to exclude an atrial clot prior to cardioversion. Although theoretically a risk, embolic events following ED cardioversion appear to be extremely rare at the time of the procedure itself, but may appear in 0% – 0.7% of patients at 30 days, depending on the use of post procedure anticoagulants. [1,3] Whether through careful interviews or conservative patient selection, emergency clinicians have shown an ability to accurately identify those patients appropriate for this treatment and demonstrate excellent patient outcomes.
If prevention of an embolic event, in particular a stroke, is a major concern in the care of AF patients, then immediate cardioversion becomes the preferred treatment of choice. Patients with atrial fibrillation have a 4-5 times greater risk of suffering an ischemic stroke with worse long term outcomes in those who do develop CVAs.  Even with therapeutic anticoagulation, patients with chronic atrial fibrillation / flutter will have a higher risk of suffering an ischemic CVA than patients in normal sinus rhythm.  Since the risk for recurrent or prolonged AF increases with the duration of time a patient remains in the arrhythmia, their risk of stroke increases proportionately. If hemorrhagic strokes or subdural hematomas secondary to anticoagulation or trauma are also included as complications, then the argument for cardioversion becomes even more compelling.  However, to be fair, patients with high CHADS2 scores may be placed on anticoagulants for 4 weeks post conversion. 
The final piece blocking emergency physicians from cardioverting and discharging their AF patients is buy in from their cardiology consultants. Most electrophysiologists will readily adopt this practice. Many of their ablation patients will revert to atrial fibrillation / flutter in the immediate post procedure period. Having an ED that can convert and discharge them avoids a readmission on their procedure record.
Convincing the clinical cardiologists of the value of ED cardioversion and discharge may be more difficult. Identifying one of the more receptive members of the staff and getting a few procedures done usually is all it takes to get even the most skeptical of individuals to consider the idea. It should be noted that once an ED begins this practice, word will spread among AF patients themselves, and they will pressure their cardiologists to avoid hospital admissions.
One final point: As a department that allows family to remain at the bedside for all procedures and resuscitations, we allow the patient’s immediately family to sit in the room during the cardioversion. Not only is it an impressive show, but it helps to spread the word about the practice when they hit social media after discharge. Nonetheless, we don’t let spouses sit too close to the defibrillator; some have been known to reach over and try giving the activation button a few extra pushes when no one is looking.
1. Stiell IG, Clement CM, Rowe BH, Brison RJ, Wyse DG, Birnie D, Dorian P, Lang E, Perry JJ, Borgundvaag B, Eagles D, Redfearn D, Brinkhurst J, Wells GA. Outcomes for Emergency Department Patients With Recent-Onset Atrial Fibrillation and Flutter Treated in Canadian Hospitals. Ann Emerg Med. 2017;69(5):562-571.
2. Hamilton A, Clark D, Gray A, Cragg A, Grubb N; Emergency Medicine Research Group, Edinburgh (EMERGE). The epidemiology and management of recent-onset atrial fibrillation and flutter presenting to the Emergency Department. Eur J Emerg Med. 2015;22(3):155-61.
3. Airaksinen KE, Grönberg T, Nuotio I, Nikkinen M, Ylitalo A, Biancari F, Hartikainen JE. Thromboembolic complications after cardioversion of acute atrial fibrillation: the FinCV (Finnish CardioVersion) study. J Am Coll Cardiol. 2013;62(13):1187-92.
4. Xavier Scheuermeyer F, Grafstein E, Stenstrom R, Innes G, Poureslami I, Sighary M. Thirty-day outcomes of emergency department patients undergoing electrical cardioversion for atrial fibrillation or flutter. Acad Emerg Med. 2010;17(4):408-15.
5. Zhang L, Po SS, Wang H, Scherlag BJ, Li H, Sun J, Lu Y, Ma Y, Hou Y. Autonomic Remodeling: How Atrial Fibrillation Begets Atrial Fibrillation in the First 24 Hours. J Cardiovasc Pharmacol. 2015;66(3):307-15.
6. Sacchetti A, Williams J, Levi S, Akula D. Impact of emergency department management of atrial fibrillation on hospital charges. West J Emerg Med. 2013;14(1):55-7.
7. Rudner J, McDougall C, Sailam V, Smith M, Sacchetti A. Interrogation of Patient Smartphone Activity Tracker to Assist Arrhythmia Management. Ann Emerg Med. 2016;68(3):292-4.
8. Mozaffarian D, Benjamin EJ, Go AS, Arnett DK, Blaha MJ, Cushman M, et al. Heart disease and stroke statistics—2015 update: a report from the American Heart Association. Circulation. 2015;131:e29–e322
9. Steinberg BA, Piccini JP. Anticoagulation in atrial fibrillation. BMJ. 2014; 14:348:g2116.
10. Inui TS, Parina R, Chang DC, Inui TS, Coimbra R. Mortality after ground-level fall in the elderly patient taking oral anticoagulation for atrial fibrillation/flutter: a long-term analysis of risk versus benefit. J Trauma Acute Care Surg. 2014;76(3):642-9
11. Airaksinen KJ. Cardioversion Of Atrial Fibrillation And Oral Anticoagulation. J Atr Fibrillation. 2015;8(3):1260.