What medication is used to treat rapid atrial fibrillation (afib)?

Management of Rapid Atrial Fibrillation

For rapid atrial fibrillation, beta blockers (metoprolol, esmolol) or non-dihydropyridine calcium channel blockers (diltiazem, verapamil) should be used as first-line agents for rate control, with specific medication choice based on patient characteristics and comorbidities. 1, 2

Initial Assessment and Management

Hemodynamically Unstable Patients

• Immediate synchronized direct-current cardioversion is recommended for patients with:
  • Ongoing myocardial ischemia
  • Symptomatic hypotension
  • Angina
  • Heart failure
  • Preexcitation (WPW syndrome) with very rapid tachycardia 1

Hemodynamically Stable Patients

• First-line medications for acute rate control:

  • Beta blockers:

    • Metoprolol: 2.5-5.0 mg IV bolus over 2 min (up to 3 doses)
    • Esmolol: 500 mcg/kg IV bolus over 1 min, then 50-300 mcg/kg/min IV
    • Propranolol: 1 mg IV over 1 min (up to 3 doses at 2-min intervals) 1, 2

  • Non-dihydropyridine calcium channel blockers:

    • Diltiazem: 0.25 mg/kg IV bolus over 2 min, then 5-15 mg/h infusion
    • Verapamil: 0.075-0.15 mg/kg IV bolus over 2 min 1, 2

Medication Selection Based on Patient Characteristics

Preferred in Patients with:

1. Normal ventricular function:

   • Diltiazem, metoprolol, or atenolol 1, 3

2. Heart failure or LV dysfunction:

   • IV amiodarone: 300 mg IV over 1 hour, then 10-50 mg/h over 24 hours
   • IV digoxin: 0.25 mg IV with repeat dosing to maximum 1.5 mg over 24 hours 1, 2

3. Bronchospasm or COPD:

   • Diltiazem or verapamil (calcium channel blockers preferred over beta blockers) 1

4. Sedentary lifestyle:

   • Digoxin may be considered (but not as monotherapy) 1

Important Considerations and Contraindications

• Digoxin:

  • Not recommended as sole agent for rate control, especially in paroxysmal AF
  • Less effective during states of high sympathetic tone
  • Onset of action delayed (60+ minutes), peak effect up to 6 hours
  • Most effective when combined with beta blockers 1, 2

• Wolff-Parkinson-White (WPW) syndrome:

  • AVOID digoxin and calcium channel blockers as they may facilitate anterograde conduction along accessory pathway, potentially accelerating ventricular rate or causing ventricular fibrillation 2
  • Amiodarone or direct current cardioversion recommended 1

• Efficacy comparison:

  • Beta blockers achieve rate control endpoints in approximately 70% of patients compared to 54% with calcium channel blockers 1
  • Recent meta-analysis suggests metoprolol may have lower rates of adverse events (10%) compared to diltiazem (19%) 4

Long-term Rate Control

• Oral maintenance dosing:

  • Metoprolol: 25-100 mg BID (tartrate) or 50-400 mg QD (succinate)
  • Diltiazem: 120-360 mg QD (extended release)
  • Verapamil: 180-480 mg QD (extended release)
  • Amiodarone: 100-200 mg QD (when other measures unsuccessful) 1, 2

• Target heart rate:

  • Resting heart rate close to 80 beats per minute
  • Heart rate on moderate exertion between 90-115 beats per minute 3

• Monitoring:

  • Assess adequacy of rate control during physical activity and at rest
  • 24-hour Holter monitoring or submaximal stress test recommended to evaluate rate control 3

Special Situations

• Tachycardia-induced cardiomyopathy:

  • A rhythm-control strategy with pharmacological therapy can be useful 1

• Persistent or refractory rapid AF:

  • Consider adding a second agent if rate control not achieved with a single drug
  • Consider cardioversion (pharmacological or electrical) 1

Remember that medication choice should be guided by patient-specific factors including comorbidities, contraindications, and hemodynamic status.