Atrial Fibrillation

Background

Causes:

1. Cardiac (atrial enlargement)
   1. HTN, CAD, valvular disease, cardiomyopathy, ACS
2. Noncardiac (increased automaticity)
   1. Hyperthyroidism, PE, hypoxic pulmonary conditions, ethanol ("holiday heart"), drugs (cocaine, TCA)
   2. Need to treat underlying cause

Diagnosis

Presentation

1. Asymptomatic - 44%
2. Palpitations - 32%
3. Dyspnea - 10%
4. Stroke - 2%
5. Also can present with decompensated heart failure, acute pulmonary edema

History

• History of afib?
  • If yes, on medication?
  • If no, was the onset recgonized?
• <48hrs duration?

Physical Exam

• Evidence of hemodynamic instability, CHF?

ECG (3 types)

1. Typical
   1. Irregularly, irregular R waves
   2. QRS rate 140-160/min
2. Large fibrillatory waves
   1. May look like flutter waves
      1. Unlike a-flutter, the fibrillatory waves are irregular
3. Slow, regular A-fib
   1. Due to complete AV block with escape rhythm

• Ischemic changes?
• Rate > 250? (think preexcitation)

Work-Up

1. ECG
2. Digoxin level (if appropriate)
3. Chem-10
4. TSH

Treatment

Anti-thrombotic therapy Chronic and paroxysmal a fib are associated with thrombus formation

Decision based on CHADS2 Score

1. Chf (1pt)
2. HTN (1pt)
3. Age>75 (1pt)
4. DM (1pt)
5. Stroke/TIA (2pts)

Score 0 - consider no treatment or ASA

Score 1 - consider coumadin or ASAn

Score 2-6 - consider coumadin (INR goal = 2-3)

All patients with valvular disease should be on anticoagulation

Cardioversion

• If unstable OR low risk for clot (risk still about 1%)
  • Low Risk = <48 hrs symptoms, new dx, no hx similar episodes, no cause found by history, no LV dysfunction, no mitral valve dz, no prior thromboembolic event
• Then anticoagulation for 3 weeks afterward

Chemical Cardioversion

1. Ibutilide (Class III)
   1. 1 mg over 10 min in pts >60 kg (or 0.01 mg/kg)
   2. can repeat dose once if not sinus within 10 min of infusion
   3. Avoid in hypoK, hypoMg, prolonged QT, torsades
   4. Efficacy superior at 90 min to IV procainamide /sotalol
   5. (monitor for few hours for polymorph VT (8% incidence), then d/c home with PO beta/Ca blockers)

Other Options:

1. Procainamide up to 1 gm IV (100 mg Q5 min) @ <20 mg/min
2. Amiodarone 0.75 mg/kg IV over 15 min. 1200 mg in 24h
3. Flecainide 300mg po

Disposition

1. New-Onset Afib (<48hrs)
   1. In the absence of angina, ECG evidence of MI, or recent infarction, no need to admit to r/o MI!
   2. If stable, no history of heart disease, no other indication for admission then most patients can be directly d/c'd from the ED after successful pharmacologic or electrical cardioversion
   3. Outpatient TTE, cardiology follow-up

Indications for hospitalization

1. Hemodynamic instability
2. Myocardial ischemia
3. CHF exacerbation 2/2 a-fib
4. Symptomatic recurrence in the ED

Complications

1. Hemodynamic compromise
   1. Lowers CO by 20-30%
   2. Impaired coronary blood flow
2. Arrhythmogenesis
3. Arterial thromboembolism

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Unstable (Cardioversion)

• Indications:

1. Ischemic CP
2. SBP < 90
3. Acute pulmonary edema
4. Altered mental status

Above must be 2/2 RVR (i.e. if HR is <130 look for other cause of above signs)

• Sedate: Etomidate 5-7mg
• 100-200j biphasic synchronized cardioversion

If shock doesn't work:

1. Verify not preexcitation
2. Incr diastolic BP to perfuse the heart
   1. Push-dose phenyleprhine
      1. Will maintain BP when give rate-control meds
      2. 50-200mcg q2-5min w/ goal dia BP >60
3. Amiodarone 150mg over 10min OR
4. Diltiazem 2.5mg/min until HR<100 or max 50mg

Stable but Symptomatic (Rate Control)

• Goal < 110bpm
• Make sure you are not slowing down a normal physiologic response
  • RVR in AF may be appropriate response to fever, hypovolemia, hypoxemia, withdrawal

Calcium-Channel Blockers

1. Preferred in pts with chronic lung disease or low EF
2. Contraindications
   1. Decompensated heart failure
   2. Preexcitation
   3. Significant hypotension

Diltiazem

1. Bolus 0.25 mg/kg (average adult dose 20mg) over 2 min
   1. If, after 15 minutes the first dose is tolerated but inadequate, re-bolus 0.35 mg/kg (average adult dose 25 mg)
   2. If pt responds to 1st or 2nd bolus start infusion at 5-15mg/hr
   3. KTPH style: load: 20mg x 10 mins, if not effective 25mg x 10 minutes, then if it responds <110/min, infusion of 10mg/hr
   4. Maximum of Dilt: 60mg in 30 minutes
2. Takes 2-5 minutes to work, last 1-4 hours
3. 94% responsive
4. If effective, can start PO dilt at 30mg QID

Beta-Blockers

1. Particularly useful with a fib associated with exercise, after an acute MI, or with thyrotoxicosis
2. Contraindicated in COPD, low EF CHF

Metoprolol

1. 2.5-5mg IVP over 2min q5 min up to 3 doses
   1. PO load with MTP 25-50mg following successful rate control with IV

Esmolol

1. Use if unsure whether pt will tolerate a BB (duration of action is only 10-20min)
2. Bolus 0.5 mg/kg over one minute, followed by 50 µg/kg/min
   1. If, after 4 minutes response is inadequate, re-bolus followed by infusion of 100 µg/kg/min
   2. If, after 4 minutes response is still inadequate, try final bolus followed by infusion of 150 µg/kg/min
   3. If necessary, infusion can be increased to maximum of 200 µg/kg/min after another four minutes

Digoxin

1. Consider as initial therapy for pts with LV dysfunction who:
   1. Do not achieve rate control targets on beta blockers alone
   2. Cannot tolerate addition of or increased doses of a beta blocker due to acute decompensated HF
   3. Would have digoxin added anyway to improve CHF symptoms independent of AF
2. Consider as initial therapy in pts with severe hypotension
3. Consider as 2nd agent in pts in whom IV BB or IV CCB has failed to control their rate
4. May take up to 6-8 hours to work
5. Dosing
   1. 0.25 mg IV q2hr up to 1.5 mg, then 0.125-0.25 mg PO or IV QD
   2. Adjust dose in presence of renal failure, amiodarone, etc

Amiodarone

1. Consider for use in pts with decompensated heart failure or those with accessory pathways
2. 2nd-line agent for chronic rate control when BBs and CCBs, alone, combined, or when used with digoxin, are ineffective
3. Load 5-7 mg/kg IV over 30 min; then 1200 mg over 24 h via continuous infusion or in divided oral doses

Stable and Asymptomatic

If mild or no symptoms and pulse only mildly elevated (<120bpm), ok to manage with PO meds

Evidence of preexcitation

1. Initial therapy is aimed at reversion to sinus rhythm
2. Avoid AV nodal agents
1. Unstable -> urgent cardioversion
   1. DC cardioversion
   2. Pharmacologic cardioversion
      1. Procainamide
         1. 20-50 mg/min until arrhythmia is controlled, hypotension occurs, QRS complex widens by 50% of original width, or total of 17 mg/kg is given; followed by continuous infusion of 1-4 mg/min
2. Stable -> try to avoid cardioversion without adequate anticoagulation

Source: UpToDate, EMCrit.org, ercast.org

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My Style

• If unstable, DC Cardioversion, SYNCHRONIZED, 100-200 J biphasic (first, give 5-7 mg of etomidate and ketamine 10-15mg IV); pad placement: anteriorly just to the right of the sternum, posteriorly just to the left of the spine = to cover both RA and LA.
• If it does not convert, move the pads (eg anteriorly to the left); organized rhythms like atrial flutter need only small amount of joules like 10-20J (just do 50J), even polymorphic VTs need lower energy; consider giving metoprolol 5mg IV before the second CV (metoprolol, sotalol, atenolol even oral can lower threshold for CV and prolongs sinus rhythm when converted; while amiodarone increases that treshold)
• If WPW, same as above; if it fails, give Amiodarone
• If it does not work, increase BP with Phenylephrine Bolus dose pressor, or Aramin/Metaraminol
• Then if BP climbs up, give Dilt if no c/i (decompensated HF/WPW/Hypotension): 20mg x 10 mins loading, repeat to 25mg x 10 mins if rate of <110 is not achieved, then 10mg/hr maintenance infusion
• If it fails, amiodarone (5mg/kg up to 300mg) IV bolus, then infusion (eg 1200 mg x 24 hours)
• If it fails: Magnesium -> Re-shock (sync) -> cardio consult -> sign-out