What is the acute oral option for rate control in a patient with rapid atrial fibrillation (AF) post coronary artery bypass grafting (CABG), already on amiodarone (Cordarone) three times a day?

Acute Oral Rate Control Options for Rapid AF Post-CABG in a Patient on Amiodarone

For acute oral rate control in a patient with rapid atrial fibrillation post-CABG who is already on amiodarone, an oral beta blocker is the recommended first-line option, with metoprolol tartrate 25-100 mg twice daily being the preferred agent. 1

First-Line Oral Options for Rate Control

• Beta blockers: These are the first-line agents for rate control in post-CABG AF patients 1

  • Metoprolol tartrate: 25-100 mg BID (oral equivalent to IV dosing) 1
  • Metoprolol succinate (XL): 50-400 mg once daily 1
  • Bisoprolol: 2.5-10 mg once daily 1
  • Carvedilol: 3.125-25 mg twice daily 1

• Nondihydropyridine calcium channel blockers: Recommended when beta blockers are inadequate or contraindicated 1

  • Diltiazem: 120-360 mg once daily (extended release) 1
  • Verapamil: 180-480 mg once daily (extended release) 1

Special Considerations for Post-CABG Patients on Amiodarone

Since the patient is already on amiodarone three times daily, consider:

• Adding a beta blocker is reasonable to control both resting and exercise heart rate in patients with AF 1
• Combination therapy: Amiodarone plus beta blocker has shown better efficacy than either agent alone in post-cardiac surgery patients 2, 3
• Digoxin: Can be added to the regimen if beta blockers are contraindicated or insufficient, especially in patients with heart failure 1
  • Oral dosing: 0.125-0.25 mg once daily 1

Algorithm for Management

1. Assess hemodynamic stability:

   • If unstable: Consider electrical cardioversion 1
   • If stable: Proceed with pharmacological rate control 1

2. Evaluate for contraindications to beta blockers:

   • If no contraindications: Add oral metoprolol tartrate 25-50 mg twice daily 1
   • If contraindicated: Use nondihydropyridine calcium channel blocker (diltiazem or verapamil) 1

3. For patients with heart failure or LV dysfunction:

   • Add digoxin 0.125-0.25 mg daily 1
   • Avoid nondihydropyridine calcium channel antagonists in decompensated heart failure 1

4. Monitor response:

   • Target resting heart rate <80 bpm for symptomatic management 1
   • Assess heart rate during exercise and adjust medications accordingly 1

Important Caveats and Pitfalls

• Avoid nondihydropyridine calcium channel blockers in patients with decompensated heart failure as they may exacerbate hemodynamic compromise 1
• Do not use digoxin as the sole agent for rate control in paroxysmal AF 1
• Careful dosing with combination therapy: When using amiodarone with beta blockers, start with lower doses of beta blockers to avoid bradycardia 1
• Consider rhythm control strategy if rate control is difficult to achieve 1
• Monitor for drug interactions: Amiodarone has numerous drug interactions and can increase the effects of beta blockers and digoxin 1

Beta blockers have demonstrated superior efficacy compared to amiodarone alone for rate control in post-CABG AF 2, 4, making them the preferred add-on therapy for patients already on amiodarone.