Comparison of Chemical vs Electrical Cardioversion of Acute Uncomplicated Atrial Fibrillation

Background Information: Atrial fibrillation is the most commonly encountered dysrhythmia in the emergency department (ED) and is associated with an increased long-term risk of stroke, heart-failure and all-cause mortality.1,2 In fact, the overall mortality rate for patients with atrial fibrillation is approximately double that of patients in normal sinus.3,4 The decision to rate vs. rhythm control patients while in the emergency department remains controversial in the literature and the method of doing so using chemical vs. electrical cardioversion also stirs up debate. Prior studies have shown the success rate of electrical cardioversion alone to be 90%.1,5 other studies have demonstrated that emergency physicians use each strategy roughly half the time.1 The authors of this study sought to determine if one of the two strategies resulted in achievement of normal sinus rhythm and discharge more quickly.

Clinical Question:

  • Does the use of a chemical-first or electrical-first cardioversion strategy of uncomplicated AF result in achievement of sinus rhythm and discharge more quickly?

What They Did:

  • A multicenter randomized control study with concealed allocation at six urban emergency departments in Canada which included a 30-day safety and patient-reported follow-up period afterwards. These hospitals varied from small community hospitals with no on-site cardiologists to large tertiary centers with electrophysiology labs and 24-hour catheterization capabilities.
  • There were two groups
    • Chemical-First: Patients were given a procainamide infusion of 17 mg/kg (up to 1500 mg) over 1 hour. Electrical cardioversion was administered if this first method was unsuccessful at converting the rhythm
    • Electrical-First: Patients were administered a synchronized electrical cardioversion of 150-200 Joules from a biphasic device. A maximum of three attempts were administered followed by a procainamide infusion if unsuccessful.

Inclusion Criteria:

  • Emergency Department patients between the ages of 18 and 75 years old
  • An episode of AF for less than 48 hours as their main diagnosis
  • CHADS2 Score of 0 or 1 (See Figure 1)
  • Taking appropriate anticoagulation

Figure 1

Exclusion Criteria:

  • Came to the ED for other reasons (ie. Trauma, back pain, gout, etc)
  • Hemodynamically instability (ie. Altered mental status, acute chest pain or heart failure, SBP < 90 mmHg)
  • Patients with atrial flutter
  • Atrial Fibrillation patients with acute underlying medical illness
  • Recent cardiac procedure within 2 weeks (ie. Coronary artery bypass graft, percutaneous intervention, ablation, pacemaker or defibrillator implantation)
  • Acute intoxication or withdrawal from alcohol or illicit drugs



  • Discharge within 4 hours of ED arrival (Started at time patient was registered at triage)


  • Median time intervals which included:
    • Registration to physician assessment
    • Assessment to randomization
    • Randomization to conversion
    • Conversion to discharge
    • Randomization to discharge
    • Registration to discharge
  • ED-based adverse events (AE)
    • Ex. Hypotension, arrhythmias
  • 30-day patient centered outcomes
    • Further physician and hospital visits
    • Quality of life assessment



  • 222 patients were screened and of the 135 eligible patients, 86 were enrolled and randomized. Two patients, one from each group, were withdrawn leaving 84 subjects to be analyzed.
    • 41 patients in the chemical-first group
    • 43 patients in the electrical-first group

Critical Results:

  • 22 of the 41 patients in the chemical first group converted with procainamide while the remainder required electrical countershock.
  • In the electrical-first group, 38 of 43 (88%) patients converted and four of those five remaining patients who received procainamide reverted back to normal rhythm.
  • All patients in both groups were discharged home. 83 out of 84 (99%) of patients were discharged home in normal sinus rhythm.
  • At 30 days, 9 of the 41 patients in the chemical-first group and 3 of the 41 patients in the electrical first group returned to the ED for recurrent AF. 2 of the patients in the chemical-first group that returned were admitted for AF that was uncontrollable in the ED.
  • Quality of life scores were similar for both groups across all domains


  • Patients were balanced fairly equal between the two groups in terms of: Age, gender, acuity, and past medical history
  • Study took place over six different urban EDs. The variability between these sites (ie. community vs. tertiary care center) increases the reproducibility of this study.
  • Measured each step of the ED visit process to see how the study intervention specifically affected these times
  • Adverse events were pre-specified based on the World Society of Anesthesia Guidelines
  • Had very strict inclusion criteria in an attempt to limit other confounding variables to the efficacy of chemical vs. electrical cardioversion
  • Secondary outcome consisted of clinically relevant 30-day patient-oriented outcomes, complete with an algorithm to ensure stroke-free survival
  • There was excellent follow-up as all patients were contacted at 3 days and all but one were contacted at 30 days (one patient refused to answer but was confirmed free from stroke or hospitalization by their primary care physician)
  • The questionnaire asked at the 3 and 30 day follow-up was very in-depth. It included items beyond mortality such as whether the patient saw their physician, revisited the ED, or had any limitations to physical and social activities.
  • Two emergency physicians blinded to allocation reviewed the ED-based AEs to see if they were truly any AE.


  • Enrollment of patients only occurred when research assistants were on duty, which only occurred during the daytime at two of the six sites. Therefore, not all eligible patients were captured at every site.
  • The primary outcome was not a patient oriented outcome but an ED operations outcome. Although the secondary outcomes were patient-oriented outcomes, they were hypothesis generating since the sample size was too small.
  • To ensure appropriate sample size calculation, the primary outcome was modified from its original outcome of ED LOS.
  • Patients with a CHADS2 score of 2 or more were not enrolled and therefore no conclusions can be made specifically on these patients from this study.
  • Neither the clinicians nor the patients were blinded
  • Availability of a nationwide ED database which allows for follow-up of patients for return ED visits is not found in many other countries as it is in Canada.
  • The authors acknowledge that the LOS could have been affected by other variables (ie. overcrowding, physician coverage, other critically ill patients in the department, and nurse/respiratory therapist availability)
  • Another potentially confounding variable was that physicians were allowed to exercise clinical judgement.
  • Recommendations used for interventions did not arise from an ED-based study and were based on 2011 Canadian guidelines
  • This study had a low rate of serious outcomes and requires a larger trial to prove safety
  • More than one-third of eligible patients declined participation, likely due to prior AF with conversion attempts. This may bias results in favor of patients with infrequent or newly diagnosed AF
  • Authors did not assess patient or physician satisfaction. Costs were also not evaluated.
  • Lastly the authors state all the physicians were “experienced” in all the treatment interventions but there is no further elaboration on how “experienced” (ie. survey approximating number of years in practice, procedural sedations, cardioversions, etc).


  • This multicenter randomized controlled trial specifically looked at which approach to treating cardioversion in ED patients with acute uncomplicated AF was effective and led to a decreased LOS. This study also demonstrated an already existing piece of knowledge regarding the treatment of uncomplicated AF patients: Regardless of the initial management strategy used, these patients have minimal discomfort and an acceptable quality of life at 3 and 30 days after their ED visit.
  • There may have been some unintentional bias introduced while attempting to enroll patients. Although some of the patients enrolled may have had a history of AF, a third of their eligible patients declined to participate thus serving to bias the results more in favor of patients with newly diagnosed AF.
  • Although the authors did explain their justification in creating their exclusion criteria, the result was a small patient population left for analysis. This and their study’s lack of power prevented them from assessing the safety profile of their interventions.
  • While this study took into consideration important patient centered outcomes like adverse events and 30-day mortality, it omitted other system-wide factors. Variables like cost, and patient/physician satisfaction were not considered.
  • Lastly, an aspect of this study that was not included in the follow-up pertains to the actual cause of the atrial fibrillation. It may have been more beneficial, in terms of preventative medicine, to the treating emergency physician if these patients followed up with a cardiologist to identify the reason(s) they may have gone into AF in the first place.

Author’s Conclusions:

  • In uncomplicated ED patients with atrial fibrillation, chemical-first and electrical first strategies appear to be successful and well tolerated. An electrical-first strategy results in significantly shorter ED length of stay.

Our Conclusion:

  • The question of rate or rhythm controlling uncomplicated atrial fibrillation patients in the ED continues to be a topic of debate. Despite its small sample size, this study helps add to our current body of knowledge and opens the discussion on which of the two cardioversion strategies is faster for sending the patient home. It also sets the stage for a larger study to be repeated, where these findings can be validated and confirmed.

Clinical Bottom Line:

  • When treating acute uncomplicated atrial fibrillation patients in the ED, emergency physicians can consider either an electrical-first or chemical-first strategy of cardioversion. Although small, this study suggests that an electrical-first approach may expedite the patient’s disposition, further research is needed to confirm this.


  1. Scheuermeyer FX et al. A Multicenter Randomized Trial to Evaluate a Chemical-first or Electrical-first Cardioversion Strategy for Patients With Uncomplicated Acute Atrial Fibrillation. Acad Emerg Med 2018. PMID: 31423687
  2. S. Stewart, et al. A population-based study of the long-term risks associated with atrial fibrillation: 20-year follow-up of the Renfrew/Paisley Study Am J Med, 2002; PMID: 12401529
  3. A.D. Krahn, et al. The natural history of atrial fibrillation: incidence, risk factors, and prognosis in the Manitoba Follow-Up Study Am J Med; 1995: PMID: 7733127
  4. Stiell IG, et al. Variation in management of recent Onset Atrial Fibrillation And Flutter Among Academic emergency departments. Ann Emerg Med 2011; PMID: 20864213
  5. Scheuermeyer FX, et al. Thirty-day outcomes of emergency department patients undergoing electrical cardioversion for atrial fibrillation or flutter. Acad Emerg Med 2010; PMID: 20370780

Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)

Cite this article as: Mark Ramzy, "Comparison of Chemical vs Electrical Cardioversion of Acute Uncomplicated Atrial Fibrillation", REBEL EM blog, October 21, 2019. Available at:

Like this article?

Share on Facebook
Share on Twitter
Share on Linkdin
Share via Email

Want to support rebelem?