What can I give a patient with rapid atrial fibrillation (a fib)?

Management of Rapid Atrial Fibrillation

For patients with rapid atrial fibrillation, intravenous diltiazem or beta-blockers are the first-line agents for rate control in hemodynamically stable patients, while immediate electrical cardioversion is recommended for hemodynamically unstable patients. 1, 2

Initial Assessment

• Evaluate for hemodynamic stability by checking for signs of shock, hypotension, acute heart failure, angina, or myocardial infarction 2
• Identify potential reversible causes of atrial fibrillation, such as thyroid dysfunction, electrolyte abnormalities, alcohol consumption, and infection 2
• Determine the duration of atrial fibrillation, if known, as this guides management decisions (less than 48 hours or greater than 48 hours/unknown duration) 2, 3

Management Algorithm

Hemodynamically Unstable Patients

• Perform immediate electrical cardioversion without waiting for anticoagulation in patients with severe hemodynamic compromise, ongoing myocardial ischemia, symptomatic hypotension, or heart failure 1
• Administer heparin concurrently, if not contraindicated, followed by oral anticoagulation with a target INR of 2-3 for at least 3-4 weeks 2, 3

Hemodynamically Stable Patients

Rate Control Medications

1. First-line agents:

   • Intravenous diltiazem: 0.25 mg/kg over 2 minutes (20 mg is reasonable for average patient); second dose of 0.35 mg/kg after 15 minutes if needed 4
   • Intravenous metoprolol: 2.5-5.0 mg IV bolus over 2 minutes, up to 3 doses 1
   • Intravenous esmolol: 500 mcg/kg IV bolus over 1 minute, then 50-300 mcg/kg/min IV 1

2. For continued rate control:

   • Continuous IV diltiazem infusion: 10 mg/h (range 5-15 mg/h) for up to 24 hours 4
   • A combination of digoxin and either a beta-blocker or calcium channel antagonist is reasonable to control heart rate both at rest and during exercise 1

3. Special situations:

   • For patients with heart failure: IV digoxin or amiodarone is recommended 1
   • For patients with accessory pathway (WPW syndrome): IV procainamide or ibutilide 1
   • Avoid calcium channel blockers and digoxin in patients with WPW syndrome 1

Comparative Efficacy

• Diltiazem achieves rate control faster than metoprolol but both agents are safe and effective 5, 6
• In a study of patients with atrial fibrillation and heart failure, diltiazem reduced heart rate more quickly than metoprolol with no significant differences in safety outcomes 7
• Beta-blockers are particularly effective in maintaining sinus rhythm after conversion of atrial fibrillation, especially in patients with myocardial infarction, chronic heart failure, or hypertension 8

Anticoagulation Considerations

• Antithrombotic therapy is recommended for all patients with AF except those with lone AF or contraindications 1
• For AF lasting more than 48 hours or of unknown duration, anticoagulate for at least 3 weeks before and 4 weeks after cardioversion 2, 3
• An alternative approach is transesophageal echocardiography to rule out left atrial thrombus before cardioversion 2

Common Pitfalls to Avoid

• Using digoxin as the sole agent for rate control in paroxysmal AF (ineffective) 1, 3
• Administering calcium channel antagonists to patients with decompensated heart failure (may worsen hemodynamics) 1
• Administering digoxin or calcium channel antagonists to patients with AF and preexcitation syndrome (may paradoxically accelerate ventricular response) 1
• Attempting cardioversion without appropriate anticoagulation in patients with AF lasting more than 48 hours 2, 3

Remember that the choice of medication should consider the patient's cardiac function, comorbidities, and the clinical setting. For most patients with normal ventricular function, diltiazem or beta-blockers are appropriate first-line agents 9.