AFIB in the ED - Dr. Sawyer

3 Major “can’t miss” causes of AFib

·      Acute myocardial infarction
·      Congestive heart failure
·      Pulmonary embolus

Other common causes of AFib

·      Thyrotoxicosis
·      Hypertensive crisis
·      Valvular disease
·      Hypokalemia/Hypomagnesaemia
·      Drugs e.g. sympathomimetics
·      Pericardial disease
·      Cardiomyopathies
·      Pheochromocytoma
·      “Holiday heart” - too much ETOH


Treatment of AF in the ED

Unstable
·      Emergency Direct Current Cardioversion (DCC)
       o   Biphasic 120J -200J
       o   Pads in the AP position

·      Reasons DCC may not work
        o   Underlying illness – CHF, thyrotoxicosis, valvular disease
        o   Dilated left atrium
        o   Longer duration of atrial fibrillation
        o   Too low energy

·      Meds:
        o   Suspicion for accessory pathway, consider one of the following:
              -  Procainamide
              -  Ibutilide
              -  Amiodarone

        o   No suspicion for accessory pathway, consider one of the following:
              -  Ibutilide
              -  Diltiazem
              -  Magnesium
              -  Amiodarone
              -  Procainamide

Stable
Start with rate control then consider disposition
·      Rate control
        o   Calcium Channel Blockers – 1st line treatment
             -  Diltiazem - 0.25 mg/kg IV over two minutes then 0.35 mg/kg IV over two minutes, if there is no response at 15 minutes      
             -  Veramamil - 2.5-5.0 mg over 2-3 minutes, then 5-10 mg in 15-30 minutes if necessary ± drip 5 mg/h

        o   β-blockers – good in increased adregnergic states
             -  Metoprolol - 5 mg IV every 5 minutes up to 15 mg
             -  Esmolol - 500 mcg/kg IV bolus over 1 minute followed by a 50-200 mcg/kg/min IV infusion. 
                                  Repeat cycle and increase drip if no effect

        o   Cardiac Glycosides – not used as monotherapy anymore
              -  Digoxin - Load 0.5 mg IV  repeat 0.25 mg every 4-6 hours for three doses

        o   Class III Antiarrythmic – beware of unintended rhythm control
              -  Amiodarone - 150 mg IV over 10 minutes followed by infusion of 1 g over six hours. May repeat bolus if needed

        o   Magnesium Sulfate - beware of unintended rhythm control
              -  MgSO4 - 2 g bolus over 10-15 minutes followed by 1 g/h infusion

Disposition - “Elective” Cardioversion in the ED

“Pro-ED Converters”
o   Safe if arrhythmia present for <48h and studies show that patients can reliably tell when their symptoms began (i.e within 48h or not)
o   Cardioversion – electrical, pharmacologic or spontaneous – of patients with recent onset atrial fibrillation carries a less than 1% embolism risk if performed within the first 48h of symptom onset
o   Early conversion ↓ need for anticoagulation
o   Many patients discharged means ↓ costs

“Anti-ED Converters”
o   Risk of thromboembolism too great
o   Patients need heparin prior to cardioversion
o   New onset AFib patients need a complete diagnostic workup
o   Use of chemical agents requires prolonged observation in ED after successful cardioversion.
o   Shouldn’t risk conversion agents or electricity when 40-71% convert spontaneously in the first 24h

Rhythm Control (a.k.a. Cardioversion)

·      Direct Current Cardioversion  is the traditional Gold Standard
       o   90% to 100% acute success rate
       o   IV/O2/Monitor/Sedation
       o   Propofol/Fentanyl or Fentanyl/Versed
       o   Airway Equipment
       o   Defib pads in the AP position

·      Chemical Cardioversion
        o   Class IA Antiarrythmic
              -  Procainamide - 100 mg IV q 5-10 minutes to maximum of 1000 mg, or 20 mg/kg IV infusion to a maximum of 20 mg/kg
        o   Class IC Antiarrythmic – “Pill in the Pocket Technique”
              -   Flecanaide – 2 mg/kg IV over 10 minutes, or 300 mg PO x1
                   -      Conversion rate 60-70% at 3 hours
                   -      91% at eight hours
              -  Propafenone - 2 mg/kg IV over 10 minutes, or 600 mg PO x1
                  -  Conversion rate up to 76% at 8 hours
         o   Class III Antiarrythmic
              -  Ibutilide - 0.01 mg/kg IV over 10 minutes (max 1 mg), may Repeat times 1 if no response after 10 minutes.
                  -      Cardioversion 33-45% in first 70 min
                  -      Risk of torsades as high as 8%

Ottawa Aggressive Protocol for emergency department patients with recent-onset atrial fibrillation

1.     Assessment
·       Stable without ischemia, hypotension or acute CHF?
·       Onset clear and less than 48 hours?
·       Severity of symptoms?
·       Previous episodes and treatments?
·       Anticoagulated with warfarin and INR therapeutic?

2.     Rate control
·       If highly symptomatic or not planning to convert
·       Diltiazem IV (0.25 mg/kg over 10 min; repeat at 0.35 mg/kg)
·       Metoprolol IV (5 mg doses every 15 min)

3.     Pharmacologic cardioversion
·       Procainamide IV (1 g IV over 60 min; hold if blood pressure < 10 mm  Hg)

4.     Electrical cardioversion
·       Consider keeping patient NPO × 6 h
·       Procedural sedation and analgesia given by emergency physician (propofol IV and fentanyl IV)
·       Start at 150–200 J biphasic synchronized*
·       Use anterior–posterior pads, especially if not responding

5.     Anticoagulation
·       Usually no heparin or warfarin for most patients if onset clearly < 48 h or if therapeutic INR for > 3 wk

6.     Disposition
·       Home within 1 h after cardioversion
·       Usually no antiarrhythmic prophylaxis or anticoagulation given
·       Arrange outpatient echocardiography if first episode
·       Cardiology follow-up if first episode or frequent episodes

7.     Patients not treated with cardioversion
·       Achieve rate control with diltiazem IV (target heart rate < 100 beats/min)
·       Discharge home on diltiazem (or metoprolol)
·       Discharge home on warfarin and arrange INR monitoring
·       Arrange outpatient echocardiography
·       Follow-up with cardiology at 4 wk for elective cardioversion

8.     Recommended additions to protocol
·       Consider transesophageal echocardiography if onset unclear
·       Alternate rhythm-control drugs: propafenone, vernakalant, amiodarone
·       If TEE-guided cardioversion > 48 h, start warfarin

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