Atrial Fibrillation (A-Fib)

Atrial Fibrillation (A-Fib)

David Ray Velez, MD

An Irregular Rhythm that Originates from Ectopic Foci in the Atrium (The Most Common Cardiac Arrhythmia)

EKG Pattern

  • RR-Interval with No Regular Pattern (“Irregularly Irregular”)
  • No Distinct P Waves

Atrial Fibrillation

Ectopic Foci

  • Pulmonary Veins – Most Common
  • Right Atrium
  • Superior Vena Cava
  • Coronary Sinus

Classification

  • Paroxysmal: Resolves Spontaneously
  • Recurrent: ≥ 2 Episodes
  • Persistent: Present for ≥ 7 Days
  • Permanent: Present for ≥ One Year

Causes

  • Fluid Overload – The Most Common Cause Postop
  • Electrolyte Derangements
  • Catecholamine Excess (Stress, Thyrotoxicosis, Epinephrine)
  • Atrial Distention (Pulmonary Hypertension, Pulmonary Embolism, Mitral Stenosis)
  • Ischemic Heart Disease
  • Hypothermia
  • Alcohol Abuse
  • Caffeine Use

Complications

  • Impaired Atrial Systolic Function (“Atrial Kick”) – Decreased Ventricular Filling
  • Increases Risk for Thromboembolism Formation within the Left Atrium
    • Risk for Stroke or Other Ischemic Events

Acute Treatment

  • Unstable: Synchronized Cardioversion (Start with 100 J and Increase to 150 J if Fails)
  • Stable: Rate Control Preferred Over Rhythm Control
    • Treat Any Underlying Causes and Correct Any Electrolyte Derangements
  • Heart Rate Goals:
    • Chronic Setting: < 110 bpm
    • Acute Setting: < 110-120 bpm (Less Well Defined)

Medications and Dosing

  • Metoprolol (β-Blockers)
    • Generally Preferred in Hyperadrenergic States (Acute MI or Postop)
    • Contraindicated in COPD or CHF
    • Dosing: 5 mg Every 5-10 Minutes as Needed (Maximum of 3 Doses)
    • May Also Consider Esmolol Drip if Necessary
  • Diltiazem (Calcium Channel Blocker/CCB)
    • Generally Superior to Amiodarone
    • Dosing:
      • Bolus: 0.25 mg/kg and Repeat a Second Bolus of 0.35 mg/kg After 15 Minutes if Needed
      • Continuous Infusion: 5-15 mg/hr
  • Amiodarone (Potassium Blocker)
    • Favored Agent in Concomitant Heart Failure
    • IV Dosing:
      • Initial Bolus: 150 mg Bolus and Repeat if Necessary
      • Continuous Infusion: 1 mg/min for 6 Hours, then 0.5 mg/min
    • Transition to Oral Amiodarone:
      • < 1 Week IV Treatment: Oral 800-1,600 mg Daily (Divided Doses)
      • 1-3 Weeks IV Treatment: Oral 600-800 mg Daily
      • ≥ 3 Weeks IV Treatment: Oral 400 mg Daily
  • Digoxin
    • Only Used as an Adjunct
    • Slow Acting and Not Used as the Sole Therapy
  • *See Antiarrhythmic Pharmacology

Anticoagulation Indications

  • Persistent > 48 Hours
  • If Cardioversion Required
  • CHADS-VASC Score ≥ 1-2
    • CHF History (+1)
    • HTN History (+1)
    • Age ≥ 65 (+1) or ≥ 75 (+2)
    • DM History (+1)
    • Stroke/TIA/Thromboembolism History (+2)
    • Vascular Disease History (MI, PAD or Aortic Plaque) (+1)
    • Sex Female (+1)