Atrial Fibrillation in the Emergency Department

Here are two cases of patients with Atrial Fibrillation.
Would you treat them in the same way?

Patient 1 is a 68 yo male presents with palpitations and vague chest tightness. He has noticed his heart racing for the last 2 hours. He has a past medical history of hypertension and smoking.
His vitals are Heart rate of 176 beats per minute, BP of 138/65, Sats of 96% on room air.

How would you treat this patient?
Patient 2 has the same characteristics as patient 1 except that he is found to have a fever and on clinical examination, has midzone crepitations in his right lung?

It’s all about primary vs secondary atrial fibrillation/flutter.

A recent review of the approach to the Emergency Department(ED) patient with atrial fibrillation/flutterwas published by the Canadian Association of Emergency Physicians(1). Here is a synopsis of that article.

STEP 1: Assessment and Risk Stratification

Is it PRIMARY or SECONDARY?

This is about, whether there is an underlying disease causing the atrial fibrillation/flutter(AF/Flut), or it is a primary event.

Primary AF/Flut is usually of sudden onset and is not due to an underlying medical condition causing.

Secondary AF/Flut is usually due to a medical cause such as sepsis or pulmonary embolism or bleeding or acute coronary syndrome. Secondary causes are usually not sudden in onset and tend to have slower ventricular rates(<150), but not always.

Why is this important?
We can aggressively treat Primary AF/Flut, however we need to treat the cause of secondary AF/Flut, not the arrhythmia itself, as aggressive rate or rhythm control in secondary causes can be harmful.

PRIMARY AF/FLUT

We need to ensure that the patient is haemodynamically stable.
An unstable patient may show the following:

• Systolic Blood Pressure <90 mmHg or signs of shock(altered mental state)
• Signs of cardiac ischaemia: chest pain, ST depression on ECG
• Pulmonary Oedema

The unstable patient needs electrical cardio version if the arrhythmia has been present for < 48hours, or in those where it has been there for >48hours, rate control.

When is it safe to cardiovert Primary AF/Flut?

Rhythm controlled is always preferred to rate control.

In this article it was safe to cardiovert if:

The patient was anticoagulated for > 3 weeks

OR

The patient is not anticoagulated for > 3 weeks but 

  Has no history of TIA or stroke 

  Has no valvular heart disease  and

• Onset < 12 hours ago OR
• Onset 12-48 hours ago and < 2 CHADS-65 Criteria (age >65, Diabetes, HT, heart failure Stroke or TIA) OR
• No thrombus on TOE

RATE Control

Rate Control is used when cardioversion(Rhythm control) is unsafe. Our target is a heart rate < 100.
If the patient is already on a beta blocker or a calcium channel blocker, more of the same medication may be used.

• Beta Blockers:
  • Metoprolol
    • 2.5-5mg IV over 2 min.
    • Repeat q15-20min for 3 doses.
    • Commence 25-50 mg PO  within 30 minutes of IV control.
    • Discharge on 25-50mg bd.
• Calcium Channel Blockers
  • Diltiazem
    • Avoid these in acute heart failure or known LV dysfunction
    • Diltiazem 0.25 mg/kg IV over 10 min repeat q15-20 min 3 doses
• Digoxin
  • Second line, slow onset- BUT FIRST LINE if hypotension and acute heart failure
    • 0.25-0.5mg loading dose then0.25mg IV Q 4-6 hours to max 1.5mg over 24 hours
    • BEWARE RENAL FAILURE

In a recent study in the American Journal of Emergency Medicine(2), “Intravenous diltiazem has higher efficacy, shorter average onset time, lower ventricular rate, less impact on blood pressure, and with no increase in adverse events compared to intravenous metoprolol.” Unfortunately IV Diltiazem is not available in many areas and certainly not in Australia.

RHYTHM Control

Electrical Cardioversion

• Pads – antero-lateral or antero-posterior
  • In a recent multicenter study in Circulation(3) it was found that anterolateral positioning was more effective for biphasic cardioversion of atrial fibrillation
• Start with 150-200J avoid low energy. AF is one of the most resistant arrhythmias, so start high.
• Note that pre-treatment with an anti arrhythmic is not recommended.

Pharmacological Cardioversion

• Procainamide 
  • IV 15mg/kg in 500ml NSaline over 60min. Maximum 1500mg
  • Beware:•Hypotension- do not use if SBP<100mmHg
  • Stop the infusion if
    • BP drops
    • Long QTc- Don’t use if QTc is >500ms
    • Stop if QTc lengthens and Check QTc after cardioversion•
• Amiodarone– NOT recommended: It has slow onset and low efficacy

STROKE PREVENTION

Who needs anticoagulation?

CHADS-65 POSITIVE (age >65, DM, HT, CCF, Stroke/TIA)

• DOAC preferred
• WARFARIN MUST BE USED in
  • Mechanical Valve
  • Moderate to severe Mitral Stenosis
  • Severe renal Impairment CrCl <30ml/min
• What if the patient is on ASPIRIN?
  • If stable CAD- stop aspirin
  • If CAD with other antiplatelets OR PCI<12 months D/W Cardiology

CHADS-65 NEGATIVE

• Consider OAC for 4 weeks, but needs shared decision making with the patient.
• If stable CAD patient can continue aspirin

If planning Trans-oesophageal Echo guided cardioversion: Anticoagulate for 4 weeks

Remember that even if the patient reverts spontaneously, anticoagulation should still be given if there are risk factors.

Anticoagulation Checklist

Dabigatran 150mg BD: 110mg bd if >80 or >75 with bleed risk

Rivaroxaban 20mg daily: 15mg daily if CrCl 30-49ml/min

Apixaban 5mg BD: 2.5mg bd if 2 of: Creat >133umol/L, Age > 80yo, Weight <60kg

Edoxaban 60mg daily: 30mg if CrCl 30-50ml/min or wt<60kg

Warfarin start 5mg daily: 1-2mg if frail, low weight or Asian descent, INR after 3-4 doses of Warfarin

Who to Admit

• Symptomatic despite treatment
• Have ACS and chest pain and ECG changes
• Acute heart failure
• NOTE: in uncomplicated Afib/Flut, admission is rarely needed
• Expect a Troponin leak

References

1. Still I.G. et al. 2021 CAEP Acute Atrial Fibrillation/Flutter Best Practices Checklist. Canadian Journal of Emergency Medicine (2021) 23:604-610.
2. Lan Q et al. Intravenous Diltiazem versus metoprolol for atrial fibrillation and rapid ventricular rate: A meta-analysis. The American Journal of Emergency Medicine. Vol51: (Jan 2022); 248-256
3. Schmidt A s et al. Anterior-Lateral versus Anterior-Posterior Electrode Position for Cardioverting Atrial Fibrillation. Circulation (2021); 144:1995-2003