INTRODUCTION
This clinical review is intended to assist emergency physicians everywhere manage patients who present to the emergency department (ED) with acute/recent-onset atrial fibrillation (AF) or atrial flutter (AFL). We will focus on symptomatic patients with acute AF or AFL, i.e. those with recent-onset episodes (either first detected, recurrent paroxysmal or recurrent persistent episodes) where the onset is generally less than 48 hours but may be as much as 7 days. These are the most common acute arrhythmia cases requiring care in the ED.
Canadian emergency physicians are known for publishing widely on this topic and for managing these patients quickly and efficiently in the ED [1–15]. This article is based primarily on the 2021 Canadian Association of Emergency Physicians (CAEP) Acute Atrial Fibrillation/Flutter Best Practices Checklist [16]. The CAEP Checklist was adapted, for use by emergency physicians, from existing high-quality clinical practice guidelines previously developed by the Canadian Cardiovascular Society (CCS) [17,18]. These guidelines were developed and revised using a rigorous process that is based on the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system of evaluation [19]. The CAEP Checklist Advisory Committee consisted of 14 emergency physicians, four cardiologists, and two patients. The 2021 process included review of new evidence [2,13,20], the 2020 CCS guidelines [17], and several commentaries that had expressed the concern of the Canadian ED community [21–23].
We focus on four key elements of ED care: assessment and risk stratification, rate and rhythm control, short- and long-term stroke prevention, and disposition and follow-up. We encourage readers to download the open access CAEP Checklist article [16] and the free smartphone application, CAEP Atrial Fibrillation Guide, available on iOS and Android platforms.
ASSESSMENT AND RISK STRATIFICATION
Is AF/AFL with rapid ventricular response a primary arrhythmia or secondary to medical causes?
While rapid AF/AFL is often a primary arrhythmia with sudden onset, it may also be secondary to medical causes (usually in patients with preexisting/permanent AF) such as sepsis, bleeding, pulmonary embolus, heart failure, acute coronary syndrome, etc. For these secondary cases, investigate and treat the underlying causes aggressively, do not cardiovert as it may be harmful, and avoid aggressive rhythm control.
Note that the rapid rate is more likely to be secondary to an underlying medical cause if there is no sudden onset or palpitations; the patient has known permanent AF, is on oral anticoagulants, and old electrocardiography (ECG) shows AF; there is no history of ED cardioversion; and the patient has fever, dyspnea, or pain.
Is the patient unstable?
Instability due to acute primary AF/AFL is uncommon, except for AF with rapid ventricular pre-excitation, which usually requires cardioversion. Consider urgent cardioversion if definitely primary and the patient has: (1) hypotension with systolic blood pressure <90 mmHg or signs of shock (e.g., altered mental status); (2) cardiac ischemia with ongoing severe chest pain or marked ST depression (>2 mm) on ECG despite therapy; or (3) pulmonary edema with significant dyspnea, crackles, and hypoxia. Note that there is often a small rise in troponin due to demand and this should not be considered acute coronary syndrome.
Is it safe to cardiovert this patient with primary AF/AFL?
When it is safe, rhythm control is usually preferable to rate control with better patient quality of life, shorter length of stay, and fewer hospital utilization of resources [12]. The guidance has recently changed based on several observational studies [24,25], and cardioversion is now considered safe under the following conditions:
• The patient has been adequately anticoagulated for a minimum of 3 weeks.
• If the patient has not been adequately anticoagulated for >3 weeks, has no history of stroke or transient ischemic attack (TIA), and does not have valvular heart disease, with one of the following:
(1) onset <12 hours ago
(2) onset 12 to 48 hours ago and there are less than two of these CHADS (congestive heart failure, hypertension, age ≥ 75 years, diabetes mellitus, stroke or TIA symptoms previously) criteria
(3) the patient is negative for left atrial thrombus on transesophageal echocardiography (TEE).
Consider delaying cardioversion if there is a recent history of frequent palpitations. Rate control may be acceptable, per patient and physician preference, e.g., older patients who are minimally symptomatic with a mildly elevated heart rate.
RATE AND RHYTHM CONTROL
Rate control for patients for whom cardioversion is unsafe
Calcium channel blockers and β-blockers are considered first line. If patient is already taking oral calcium channel blocker or β-blocker, choose same drug group first. If difficulty achieving adequate rate control, consider using the other first-line agent, intravenous (IV) digoxin, or cardiology consultation. Aim for a target heart rate of <100 beats/min at rest and <110 beats/min walking.
Calcium channel blockers
Calcium channel blockers should be avoided if acute heart failure or known left ventricular dysfunction (point-of-care ultrasound may be helpful). Suggest diltiazem 0.25 mg/kg IV over 10 minutes; repeat every 15 to 20 minutes at 0.35 mg/kg up to three doses within 1 hour. Start 30 to 60 mg orally within 30 minutes of effective IV rate control. Discharge on 30 to 60 mg four times a day or extended release 120 to 240 mg once daily.
Rhythm control
Either pharmacological or electrical cardioversion is acceptable, per patient and physician preference. Consider previous episodes and if one does not work, try the other. Pretreatment with rate control agents is not recommended as it is ineffective and delays definitive treatment [10]. We prefer IV medications as they are much faster in onset than oral agents such as propafenone and flecainide.
Pharmacological cardioversion
We recommend procainamide IV 15 mg/kg in 500 mL normal saline over 60 minutes, to a maximum of 1,500 mg [5]. Avoid if systolic blood pressure <100 mmHg or corrected QT interval >500 msec. Interrupt infusion if blood pressure drops and administer IV fluid bolus.
While IV amiodarone may be useful for postoperative or medically ill patients, it is not recommended for acute AF in the ED as it is slow-acting and has low efficacy. Depending on where you live other options include IV vernakalant, propafenone, flecainide, and ibutilide (which may cause torsades de pointes).
Electrical cardioversion
Electrical cardioversion can be easily performed by ED physicians without need for cardiology or anesthesia. We recommend a minimum of two staff (registered nurse and registered respiratory therapist or two registered nurses) and a second physician is ideal if feasible [14]. Use procedural sedation as per local practice, administered by the ED physician.
Start with 150 to 200 J synchronized—avoid starting with low energy level or the patient may awaken prematurely. Both the anterolateral or anteroposterior paddle/pad positions are equally effective [26]. Avoid sternum and breast tissue. If unsuccessful, apply pressure with paddles and try the other position. Many patients can be discharged as soon as 30 minutes after conversion if treated with IV procainamide or electrical cardioversion.
Rapid ventricular preexcitation (Wolff-Parkinson-White syndrome)
Urgent electrical cardioversion is usually required. Some patients, however, may be stable in which case use IV procainamide. Atrioventricular nodal blocking agents are contraindicated (digoxin, calcium channel blockers, β-blockers, adenosine, amiodarone) and could lead to life-threatening deterioration.
STROKE PREVENTION
Anticoagulation
Antithrombotic therapy prescribed at discharge is for long-term stroke prevention. We do not recommend use of IV heparin or oral anticoagulants (OACs) for cardioversion in the ED.
If the patient is “CHADS-65 positive (any of age ≥65 years, diabetes, hypertension, heart failure, stroke/TIA)”, prescribe OAC prior to discharge. Consider shared decision-making to include patients’ preferences with regards to risks and benefits. Generally direct-acting OACs (DOACs) are preferred over warfarin. Use warfarin (DOACs contraindicated) if the patient has a mechanical valve, moderate-severe mitral stenosis, or severe renal impairment (creatinine clearance [CrCl] <30 mL/min). For patients with coronary artery disease, discontinue aspirin if stable. If patient is taking other antiplatelets or had percutaneous coronary intervention <12 months, consult cardiology.
If “CHADS-65 negative,” OAC might be considered for a 4-week period after careful consideration of risks and benefits and a shared decision-making process with the patient [27]. Ensure patient is aware anticoagulation will be discontinued after 4 weeks.
If TEE-guided cardioversion is performed, DOACs should be started immediately for 4 weeks.
Patients who convert spontaneously before ED treatment should generally be prescribed OAC according to the CHADS-65 criteria.
DOACs and warfarin
We recommend the Thrombosis Canada application for details. Avoid in pregnancy or breastfeeding. Consult nephrology or thrombosis if CrCl <30 mL/min.
Dabigatran
Use dabigatran 150 mg twice a day; use 110 mg twice a day if age >80 years, or >75 years with bleeding risk.
Apixaban
Use apixaban 5 mg twice a day; use 2.5 mg twice a day if two of the following: (1) serum creatinine >133 μmol/L; (2) age >80 years; or (3) body weight <60 kg.
Edoxaban
Use edoxaban 60 mg daily; use 30 mg daily if CrCl 30 to 50 mL/min or weight <60kg; important drug interactions.
Warfarin
If indicated, initiate at 5 mg daily (1–2 mg daily if frail, low weight, Asian descent). Heparin bridging not required unless TEE-guided cardioversion. Arrange for international normalized ratio (INR) testing and review after three or four doses of warfarin. Subsequent warfarin doses should be communicated to patient on the day of the INR test.
DISPOSITION AND FOLLOW-UP
Admission to hospital
Admission is rarely required for uncomplicated acute AF/AFL patients unless they are highly symptomatic despite adequate treatment; have acute coronary syndrome with significant chest pain, troponin rise, and ECG changes; or have acute heart failure not improved with ED treatment. We do not recommend routine measurement of troponin.
Follow-up issues
We recommend physician follow-up within 7 days if a new prescription for warfarin or rate control agents. We suggest cardiology or internal medicine follow-up in 4 to 6 weeks, unless already followed or if new medications prescribed. Provide a patient handout (e.g., from Thrombosis Canada) describing new medications, AF, and follow-up. Early renal function monitoring is important for newly prescribed DOACs. Do not initiate oral antiarrhythmic agents like amiodarone or propafenone in the ED, as these are better left to cardiologists. If sinus rhythm achieved, there is generally no need to initiate β-blockers or calcium channel blockers.
CONCLUSION
Modern management of acute AF/AFL includes aggressive rhythm control with drugs or electricity, performed by ED physicians without the need for consultation. Most patients can be rapidly discharged home after treatment and resume normal activities without the need for hospitalization or delayed cardioversion. Important concepts include differentiating between primary and secondary tachyarrhythmias and when it is safe to cardiovert versus using rate control. Understanding how to prevent stroke is equally important.
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