Atrial fibrillation (main)

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
  • Asymptomatic - 44%
  • Palpitations - 32%
  • Dyspnea - 10%
  • Stroke - 2%
  • 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)
  • Typical
    • Irregularly, irregular R waves
    • QRS rate 140-160/min
  • Large fibrillatory waves
    • May look like flutter waves
      • Unlike a-flutter, the fibrillatory waves are irregular
  • Slow, regular A-fib
    • Due to complete AV block with escape rhythm
  • Ischemic changes?
  • Rate > 250? (think preexcitation)

Work-Up

• ECG
• Digoxin level (if appropriate)
• Chem-10
• TSH

Treatment

• See Atrial Fibrillation (RVR)
• Anti-thrombotic therapy
  • Chronic and paroxysmal a fib are associated with thrombus formation
  • Decision based on CHADS2 Score
    • Chf (1pt)
    • HTN (1pt)
    • Age>75 (1pt)
    • DM (1pt)
    • 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

• New-Onset Afib (<48hrs)
  • 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
    • Outpatient TTE, cardiology follow-up
• In the absence of angina, ECG evidence of MI, or recent infarction, no need to admit to r/o MI!
• Indications for hospitalization:
  • Hemodynamic instability
  • Myocardial ischemia
  • CHF exacerbation 2/2 a-fib
  • 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

See Also

Atrial Fibrillation (RVR)

Source

1/30/06 DONALDSON (adapted from Lampe), UpToDate