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SGEM#88: Shock Through the Heart (Ottawa Aggressive Atrial Fibrillation Protocol)

SGEM#88: Shock Through the Heart (Ottawa Aggressive Atrial Fibrillation Protocol)

Podcast Link: SGEM88a
Date:  September 23rd, 2014 

Guest Skeptics: Dr. Anand Swaninathan or Swami as his is better known. Swani is an assistant program director at NYU/Bellevue Hospital in the department of EM. He is also part of the REBEL EM Alliance.

Case Scenario: A 35-year-old woman presents to the ED with palpitations. She states that she woke up this morning and went for a run and began feeling her heart race. She stopped and rested but her heart rate wouldn’t come down and it felt irregular. This all started about 2 hours ago. Her vitals are unremarkable except that her heart rate is 140 bpm and irregular.


Question: What is the effectiveness and safety of the Ottawa Aggressive Protocol to perform rapid cardioversion and discharge of patients with these arrhythmias?


d5c7a8d36ae3db4dc1874640a99379e7Background: Atrial fibrillation is one of the most common dysrhythmias encountered in the ED. Patients with chronic AF often present with increased heart rates, chest pain and weakness among other presentations. There has been a debate going on for a number of years as to which is the best strategy to address these patients, rate or rhythm control.  This debate has raged for years with little end in site.

Dr. Ian Stiell and colleagues published an article in 2011 in Annals looking at variation in Recent-Onset atrial fibrillation management in Canada and found a ton of variability. Rhythm control was selected in 42-85% of patients across hospitals and electricity was chosen as the primary strategy for rhythm control in 7-69%. Lots of diffing opinions.

In the USA there’s a lot of fear of cardioversion. Actually, the fear is of cardioverting and the patient throws a clot. What happens is that a lot of patients are rate controlled, admitted and we let cardiology sort it out.  With all this variability in practice, Stiell and colleagues sought to show that their protocol was both effective and safe.

Lauren Westafer and Jeremy Faust from FOAMCast recently did an excellent job covering the background on atrial fibrillation and flutter. Don’t FOAM it alone. While you are at it check out their new word “Rosenalli”. This is the melding of core Emergency Medicine texts, Rosen’s and Tintinalli.

Article: 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): 181-91

  • Population: 660 Consecutive, retrospective cohort of ED patients presenting with a primary diagnosis of recent-onset atrial fibrillation or flutter. Ottawa Hospital Civic Campus ED between June 2000-June 2005
    • Exclusions: Chronic or persistent/longstanding AF, patients with symptoms longer than 48 hours or unknown duration, and patients with another diagnosis necessitating admission.
  • Intervention: Ottawa Aggressive Protocol (Box 1) Basically, rate control if very symptomatic or not being cardioverted. Otherwise, procainamide infusion 1 gram over 60 min IV and if this failed, electrical cardioversion. Of note, procainamide held if patient unstable or had hx of failing procainamide in past.
  • Comparison: None
  • Outcome: Conversion to sinus rhythm, discharge from the hospital, discharge in atrial fibrillation 

Authors’ Conclusions: “The Ottawa Aggressive Protocol is effective, safe and rapid and has the potential to significantly reduce hospital admissions and expedite ED care.”

Peace_Tower-OttawaOttawa Aggressive Atrial Fibrillation Protocol: Once the patient is assessed and it’s determined that their symptoms began  <48 hours prior to presentation, they were entered into the protocol. Rate control was given if either the patient was highly symptomatic while awaiting cardioversion or if cardioversion was not going to be pursued. Rhythm control was then initiated with an infusion of procainamide 1000 mg over 60 minutes. If procainamide worked, great the protocol was completed. If it didn’t work, the patient moved on to electrical cardioversion. Chemical cardioversion was skipped in patients who were unstable or they had a history of AF with failure of procainamide. They then go on to discuss anticoagulation and disposition.

Screen Shot 2014-09-23 at 8.26.22 AM

checklist-cartoonCritical Appraisal Check List for Cohort Study:

1. Did the review ask a clearly focused question? – Yes. Is it safe and efficacious to implement the Ottawa Aggressive Protocol in patients with new onset atrial fibrillation.

2. Did the authors use an appropriate method to answer the question? – Yes, for the question that was asked.  They weren’t looking to compare rhythm control versus rate control for a patient centered outcome but simply to evaluate the efficacy of this approach. It would of course be great to see a RCT to answer the real question: “What is better rate or rhythm control”?

3. Was the cohort recruited in an acceptable way? – Yes. Recruitment was of consecutive patients. No one aside from the predetermined exclusions was left out.

4. Was the exposure accurately measured to minimize bias? – Yes. An objective outcome measure was looked at here – was the patient in sinus rhythm or not? Was the patient discharged or not? Although discharge does take into account a more subjective evaluation.

5. Was the outcome accurately measured to minimize bias? – Yes. Hard to bias whether the patient in sinus or not.

6. Have the authors identified all important confounding factors and were these taken into account in the design? – Yes.

7. Was the follow up of subjects complete and long enough? – The primary endpoint was simply looking at whether the patient converted or not. The also looked at 7-day relapse rates. We can argue whether 7 days is long enough or if they should have looked at 14, 30 or 60 days instead. Often when you read cardiology literature they have a 30d outcome. There are a couple of questions with the length of follow-up. How long do you feel responsible for someone you discharged from the emergency department? And from a medical legal standpoint, how long should you be held accountable?

8. What are the results of this study? – As stated previously, they found that 96.8% of patients were discharged home and 90% were discharged in sinus rhythm. The relapse rate at 7 days was 8.6%.

9. How precise are the results? Little unsure, they calculated descriptive statistics using proportions, means or medians with intra quartile ranges. It would have been nice to see some 95% confidence intervals around some of the key results.

10. Do you believe the results? – Yes. I think the endpoint they were focused on was a hard one. Did this protocol lead to rhythm control and the answer is that it did in 90% of patients who were eligible to enter the protocol. Additionally, the safety outcome is a hard one as well – did anyone have a thromboembolic event? Easy to figure out.

11. Can the results be applied to the local population? –  Yes. One interesting thing I found here was that a lot of these patients had been cardioverted for atrial fibrillation in the past. That may not be everyone’s typical population although it is mine. Yes, I too have seen patients more than once in the emergency department for atrial fibrillation and cardiverted them back to normal sinus rhythm.

12. Do the results of this study fit with the available evidence? – Yes. There’s other literature that shows similar conversion rates so this isn’t far outside of what we’d expect.

Key Results:

  1. 660 patients recruited
  2. 95.2% with atrial fibrillation, 4.9% with atrial flutter
  3. Procainamide conversion rate was 58.3%
  4. Of the 243 patients who underwent electrical cardioversion, 91.7% success rate
  5. 96.8% of patients were discharged home and 93.3% of them were in sinus rhythm upon discharge.
  6. Adverse events were seen in 7.6% and there were no cases of torsades de pointes or CVA or death.
  7. Median LOS: 4.9 hours. 3.9 hours in those converting with procainamide, 6.5 hours in those requiring electrical cardioversion.
Dr. Anand Swaminathan

Dr. Anand Swaminathan

Does this Change What We Do? – Hard to say. I still think at least in the US, there’s a lot of concern about converting someone and throwing an embolism. There was a recent letter in JAMA that questioned whether the cutoff for cardioversion should be 48 hours or 12 hours. They found that the risk of thromboembolic event was 0.3% in the group converted at < 12 hours and 1.1% from 12-48 hours. Even though this rate is still quite low, it’s probably higher than we’d like to see. It is important to note that in patients with 3 weeks of anticoagulation who are then cardioverted, the thromboembolic rate is still up to 0.8%. I know this was plastered all over Social Media when it came out and Ian Stiell himself said that his group is looking into these numbers as this may change recommendations.

Aside from the limitation of thromboembolic phenomena, I think many US EPs would rather defer the procedure, along with the procedural sedation, to the cardiologists and inpatient guys. But I think this is the wrong reason to not cardiovert. The other day, we had a young guy come in with recent onset AF of about 2 hours and we had him sedated and cardioverted within 15 minutes. It just doesn’t take that long to do this.

It is these controversial issues in medicine that often teach us the most. When there is no clear answer on what is the best approach it makes us think even harder. New onset rapid atrial fibrillation is one of those areas.

We all want to give the best care to patients based on the best evidence. However, sometimes the best evidence is weak. This is truly a “classic” example of…we need more information. Until we have that more definitive study it motivates us to know both sides of the argument. To understand why some evidence supports rate control and other evidence supports rhythm control as an optimal strategy.

Screen Shot 2014-01-28 at 12.27.19 PMRemember that evidence based medicine is not just about literature. EBM was originally defined as the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. The literature is just one part of EBM. It also involves clinical expertise and the patient’s unique situation and personal values. It is where these three important things over lap that you get the “best” care.

EBM is about increasing patient’s choices not decreasing choices. And this is done using shared decision-making. So ultimately, the EBM answer to any clinical question, as my mentor Dr. Anderw Worster taught me so well is…it all depends.


Bottom Line: The Ottawa Aggressive Protocol appears to be highly effective in converting patients with recent onset atrial fibrillation or flutter back to sinus rhythm. In this cohort of 660 patients, there were no thromboembolic events and the relapse rate was 8.6% at 7 days.


Case Resolution: You discuss the options with your patient and she elects for chemical cardioversion. After the administration of procainamide, she is still in atrial fibrillation. She then elects for electrical cardioversion. You perform procedural sedation and convert the patient with 150J biphasic and she converts to sinus rhythm. 1 hour after the procedure, you discharge home for follow up with your local cardiologist.

Keener Kontest: Last weeks winner was Dr. Matt Hallanger a PGY-2 in EM at Mercy St. Vincent Medical Center, Toledo, Ohio. He knew that paracetamol or acetaminophen abandoned as a drug for nearly 60 years after its first Patient trial 1899 for fear that it induced methemoglobinemia (which it does not).

Listen to the podcast to hear this weeks keener question. If you know the answer send an email to TheSGEM@gmail.com with “keener” in the subject line. The first person to correctly answer the question will receive a cool skeptical prize.


Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.