Atrial fibrillation with RVR

Unstable

• Synchronized cardioversion (100-200J)
• Indications: ischemic CP, SBP < 90, acute pulmonary edema, AMS
• 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 DBP >60
3. Amiodarone 150mg over 10min OR diltiazem 2.5mg/min until HR<100 or max 50mg

Stable

• Goal <120bpm
  • Make sure you not slowing down a normal physiologic response (e.g. fever, hypoxia, etc)

Cardioversion

• Consider for:
  • Symptoms <48hr
  • New diagnosis
  • No history of similar episodes
  • No LV dysfunction
  • No mitral valve disease
  • No prior thromboembolic event

Calcium-Channel Blockers

• Preferred in pts with chronic lung disease or low EF
• Contraindications:
  • Decompensated heart failure
  • Preexcitation
  • Significant hypotension
• Diltiazem
  • Bolus 0.25 mg/kg (average adult dose 20mg) over 2 min
  • If, after 15min 1st dose is tolerated but inadequate re-bolus 0.35 mg/kg
  • If pt responds start infusion at 5-15mg/hr or give PO dilt 30mg QID

Beta-Blockers

• Particularly useful when A-fib a/w exercise, after acute MI, or w/ thyrotoxicosis
• Contraindications:
  • COPD
  • Low EF
  • CHF
• Metoprolol
  • Bolus 2.5-5mg IVP over 2min q5min up to 3 doses
  • If pt responds PO load with 25-50mg
• Esmolol
  • Use if unsure whether pt will tolerate a BB (duration of action is only 10-20min)
  • Bolus 0.5 mg/kg over one minute, followed by 50 µg/kg/min
  • If, after 4min response is inadequate, re-bolus followed by infusion of 100 µg/kg/min
  • If, after 4min response is still inadequate, try final bolus followed by infusion of 150 µg/kg/min
  • If necessary, infusion can be increased to maximum of 200 µg/kg/min after another four minutes

Digoxin

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

Amiodarone

• Consider for pts with decompensated heart failure or those with accessory pathways
• 2nd-line agent for chronic rate control when BBs and CCBs, alone, combined, or when used with digoxin, are ineffective
• Load 5-7 mg/kg IV over 30 min; then 1200 mg over 24hr 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. Avoid AV nodal agents
2. Unstable:
   1. Synchronized cardioversion
   2. Procainamide (if cardioversion unsuccessful)
      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
3. Stable:
   1. Try to avoid cardioversion without adequate anticoagulation

See Also

• Atrial Fibrillation (Main)

Source

• UpToDate
• EMcrit Podcast 20