Why would we even consider cardioverting Atrial Fibrillation with Rapid Ventricular Response (AF w/ RVR) patient in the ED?
62 year old male presents with palpitations and shortness of breath that started abruptly 2 hours prior to arrival. He takes no medications on a daily basis and has no significant health history. The ECG suggest atrial fibrillation with rapid ventricular response. What is your plan for disposition?
First, there is no evidence that delayed cardioversion with full anticoagulation and echocardiogram to rule out clot in the atrium is any safer than cardioverting the patient in the ED!
Do you have to go straight to cardioversion?
There are several options for the hemodynamically stable patient in the ED.
Option One: Rate control (your choice Cardizem versus Lopressor), give a dose of low molecular weight heparin, and admit all patients to the telemetry unit. This is still done, but I’m not sure why… The article by Blecher, et al in May 2012 CJEM suggested that rate control prior to attempted cardioversion decreases the success rate. It certainly flies in the face of what I would think (that pretreatment with rate control would increase successful conversion to sinus).
Option Two: Cardiovert right now- either chemically with procainamide (1 gram IV over an hour, it is costly) or straight to electricity. I’d say about ~80% of the time, the experienced patients want to go straight to electricity and not mess around. They also don’t want to stay in the hospital to have the same procedure performed in 24 hours. The new onset atrial fibrillation patients may request admission and rate control more often than a patient with previous episodes, but even the majority of first-timers go for cardioversion during the current ED visit.
Option Three: Do no ED cardioversion at all and discharge to home. Anticoagulate and refer the patient to cardiology. You can also start your patient on LMWH and set them up for an urgent TEE/2D Echo to look for atrial clots. I am not a big proponent of this option as the patient may not follow up and may not take the anticoagulation etc.
Is it safe to cardiovert AF w/ RVR patients?
December 2011 Annals of Emergency Medicine article titled: Is discharge to home after emergency department cardioversion safe for the treatment of recent onset atrial fibrillation This was a “Best Available Evidence” review that looked 5 papers addressing the safety of ED cardioversion.
- The authors’s synopsis of the 5 reviewed papers was that most of the complications related to cardioversion comes from procedural sedation
- Other complications identified:
- Chest wall burns
- Zero reported post cardioversion thromboembolic events
- 2 episodes of ventricular tachycardia
- One v-tach converted spontaneously and 1 was successfully shocked
- Other complications identified:
Sometimes in the back of our minds, we worry that we are going to cause a more serious arrhythmia if we shock a patient with a-fib. There have been a few reported cases of ventricular tachycardia but it is extremely rare, and the two in this paper were short lived.
Are we going to cause a stroke
Combining the outcome data of the 5 studies in this ‘best available evidence’ paper, there were zero reported post cardioversion thromboembolic events after ED discharge with follow up periods ranging from 7 to 30 days.
Clots do form within 48 hours. However, all of the clinical data generated so far validates this practice. It indicates that while clots can form within 48 hours, patients treated within this window without obligatory pre-cardioversion anticoagulation appear to be stable for discharge with a low risk of complications.
What about the literature suggesting the risk of thromboembolic complications at 12 and 24 hours is higher than anticipated? Nuotio, I et al. Time of cardioversion for acute atrial fibrillation and thromboembolic complications. JAMA. 2014
- • They did a retrospective study on a population of patients who was discharged from the ED after cardioversion for atrial fibrillation and followed them for 30 days. They found that the incidence of thrombotic events was higher than previously quoted, suggesting that the risk started at 12 hours from symptom onset. Citing < 12 hours from symptom onset the risk was only 0.3% and > 12 hours, increased to 1.1% risk. The highest risk being identified in women.
Weigner, MJ et al. Risk for clinical thromboembolism associated with conversion to sinus rhythm in patients with atrial fibrillation lasting less than 48 hours. Ann Intern Med. 1997
- Three hundred fifty seven hospitalized patients converted to sinus rhythm within 48 hours of a fib onset. Some converted spontaneously and some were cardioverted. Out of those 357, there were three thromboembolic events shortly after conversion from fib to sinus. All three of these patients were in their 80s and all three converted spontaneously.
Should we give a dose of LMWH before ED cardioversion?
There are several theories addressing why atrial fibrillation causes clots to form in the atrium. One is that prolonged fibrillation leads to stagnation of blood and subsequent clot formation. Another is that conversion from fib to sinus, either spontaneously or via cardioversion, depresses left atrial function which leads to clotting (“cardiac stunning”). We worry about both of these when considering cardioversion of ED patients. Regarding theory two, clot formation as a result of cardioversion, wouldn’t it make sense to give some anticoagulation like LMWH at the time of cardioversion to decrease the risk of clot formation? In the 1997 Annals of Internal Medicine study mentioned above, no difference in thromboembolic stroke risk was seen between patients who did and did not receive acute anticoagulation with either warfarin or heparin. The study was not designed to specifically to look at such an outcome measure so do not take this to mean there is no validity in such an approach.  The American College of Chest Physicians, recommend considering acute heparin for high risk patients getting cardioversion, but even they recognize that there’s no evidence to support this approach. 
When discharging a patient with new onset atrial fibrillation after a successful cardioversion
“Atrial fibrillation has a high rate of recurrence.”
“You need to establish care with a cardiologist to get an echocardiogram and discuss long term a fib management.”
If this is a patient with new onset a-fib or one who is not on an anti-platelet agent or anticoagulant, I would also calculate the patient’s CHA2 DS2- VASc score on MDcalc (thanks Dr.Walker for the new ios app) and give them a printout showing their future stroke risk. Many of these folks are not even taking aspirin – I at least start them on that.
Should you start oral anticoagulants in the ED? I personally am on the fence on this topic. I have opted to calculate patients score and if > 1 start them on short term anticoagulation for ~ 3 weeks and allow the primary clinician or cardiologist to determine if they would like to continue such therapy for a longer duration of time, if the patient has been in atrial fibrillation for greater than 12 hours from arrival.
What to do with patients whose duration is unclear?
If you don’t know, error on the side of rate control unless anticoagulated. Cardioversion is less likely to be effective if they are in the rhythm for a longer time.
- You can confirm therapeutic anticoagulation with warfarin. Unfortunately we are unable to do so, if the patient is taking a newer agent. You need to find out exactly how compliant they have been. Are they taking the medication correctly? If they are non-compliant or appear unreliable, don’t cardiovert.
What about atrial fibrillation from a secondary cause i.e. Sepsis?
For these patients, the goal should be to treat and stabilize the underlying medical condition. If the atrial fibrillation persists, then you can consider some of the concepts.
What is the recommended starting energy level?
There is no solid evidence. I start at 200J biphasic.
What happens if the cardioversion is unsuccessful?
I will attempt up to 3 successive shock attempts before terminating the effort. When it hasn’t been successful, there is usually some secondary cause. For example, a patient with atrial fibrillation who didn’t respond to cardioversion was later found to have a PE.
Give these patients urgent rate control. They are risk-stratified according to risk of thromboembolic disease and anticoagulated as needed.
We are experts in sedating patients. Electrical cardioversion, is safe!
Hijinio Carreon DO
Special thanks to Dr. Rob Orman for his contribution on this Blog post
1. Stiel, 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 May;12(3):181-91.
2. Von Besser, K et al. Is discharge to home after emergency department cardioversion safe for the treatment of recent-onset atrial fibrillation? Ann Emerg Med. 2011 Dec;58(6):517-20. doi: 10.1016/j.annemergmed.2011.06.014. Epub 2011 Jul 29.
3. Weigner, MJ et al. Risk for clinical thromboembolism associated with conversion to sinus rhythm in patients with atrial fibrillation lasting less than 48 hours. Ann Intern Med. 1997 Apr 15;126(8):615-20. PMID:9103128
4. Blecher, GE et al. Use of rate control medication before cardioversion of recent-onset atrial fibrillation or flutter in the emergency department is associated with reduced success rates. CJEM. 2012 May;14(3):169-77.
5. Nuotio, I et al. Time of cardioversion for acute atrial fibrillation and thromboembolic complications. JAMA. 2014 Au 13;312(6):647-9. PMID: 25117135
6. Singer DE et al. Antithrombotic therapy in atrial fibrillation: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest. 2008 Jun;133 (6 Suppl):546S-592S. doi: 10.1378/chest.08-0678.