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 (preferably through central venous access) OR diltiazem 2.5mg/min until HR<100 or max 50mg

Stable

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

Cardioversion

• If cardioversion is considered, pretreatment with rate or rhythm control medications can reduce effectiveness
• Consider for:
  • Symptoms <48hr
  • New diagnosis
  • No history of similar episodes
  • No LV dysfunction
  • No mitral valve disease
  • No prior thromboembolic event
  • Already Anticoagulated

Anticoagulation Prior to Cardioversion

• Anticoagulation with Heparin or LMWH should be considered before cardioversion if time permits, otherwise immediately after cardioversion. (unless you are sure it has been <48 hours since onset of afib)

• Generally cardioversion while anti-coagulated is believed to be safe with a 1.3% risk of thromboembolism if on aspirin or other anticoagulant However the risk may be as great as 2% risk after 48 hours and preference should be given to anticoagulation prior to cardioversion in longer cases

Calcium-Channel Blockers

• Preferred in patients with chronic lung such as Asthma and COPD

Contraindications:

1. Decompensated heart failure
2. Preexcitation (especially in pediatrics)
   • 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 patient 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
• Also long-term beta blocker improves patient survival whereas non-dihydropyridine calcium channel blockers may even worsen outcomes. Important to consider if a patient will most likely be started on a beta blocker upon discharge then strongly consider using the agent for acute conversion if they do not have any relative contraindications.

Contraindications:

1. COPD
2. Asthma
3. Decompensated heart failure
4. Hypotension

Metoprolol

• Bolus 2.5-5mg IVP over 2min q5min up to 3 doses
• If patient responds orally load with 25-50mg

Esmolol

• Use if unsure whether patient will tolerate a beta blocker since the duration of action is only 10 minutes
• 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 patients 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

Dosing

• Load 3-7 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. Unsynchronized cardioversion (200J)
   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

Role of Echocardiography

If possible bedside echocardiography should be performed in patients with uncontrolled atrial fibrillation in order to help stage the LV function and determine treatment strategy. In those with severe LV dysfunction there will of course be avoidance of negatively inotropic agents such as beta blockers and calcium channel blockers in the acute decompensated phase.

See Also

• Atrial Fibrillation (Main)
• Ottawa Aggressive Cardioversion Protocol

External Links

• ALiEM - BB vs CCB
• Crashing Afib - EMCrit