What is the comparison between Amiodarone (Amio) and Diltiazem (Dilt) for conversion of new onset atrial fibrillation (AFib) with rapid ventricular response (RVR)?

From the Guidelines

For new onset atrial fibrillation with rapid ventricular response (AFib with RVR), diltiazem is generally preferred as first-line therapy over amiodarone due to its faster rate control and lower risk of adverse effects.

Key Considerations

• Diltiazem typically works faster for rate control, with an initial IV bolus of 0.25 mg/kg over 2 minutes, followed by a second bolus of 0.35 mg/kg if needed after 15 minutes, as recommended by the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1.
• A maintenance infusion of 5-15 mg/hour can then be started, effectively blocking AV nodal conduction and quickly reducing ventricular rate.
• Amiodarone is typically reserved for patients with heart failure or hypotension, as diltiazem can worsen these conditions due to its negative inotropic effects, as noted in the 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation 1.
• Amiodarone is given as a 150 mg IV bolus over 10 minutes, followed by 1 mg/min infusion for 6 hours, then 0.5 mg/min, but it works more slowly for acute rate control and has more potential adverse effects, including thyroid dysfunction, pulmonary toxicity, and liver abnormalities with prolonged use.

Monitoring and Administration

• Blood pressure monitoring is essential with either medication, and patients should be on continuous cardiac monitoring during administration.
• The choice between diltiazem and amiodarone should be based on individual patient factors, including the presence of heart failure or hypotension, and the potential risks and benefits of each medication, as outlined in the guidelines 1.

From the FDA Drug Label

Diltiazem slows the ventricular rate in patients with a rapid ventricular response during atrial fibrillation or atrial flutter Diltiazem converts paroxysmal supraventricular tachycardia (PSVT) to normal sinus rhythm by interrupting the reentry circuit in AV nodal reentrant tachycardias and reciprocating tachycardias, e.g., Wolff-Parkinson-White syndrome (WPW). Apart from studies in patients with VT or VF, described below, there are two other studies of amiodarone showing an antiarrhythmic effect before significant levels of DEA could have accumulated A placebo-controlled study of intravenous amiodarone (300 mg over 2 hours followed by 1200 mg/day) in post-coronary artery bypass graft patients with supraventricular and 2- to 3-consecutive-beat ventricular arrhythmias showed a reduction in arrhythmias from 12 hours on

The answer to the question of Amio vs Dilt for conversion of new onset AFib RVR is that:

• Diltiazem is effective in slowing the ventricular rate in patients with a rapid ventricular response during atrial fibrillation or atrial flutter.
• Amiodarone has shown an antiarrhythmic effect in patients with supraventricular arrhythmias, but the provided information does not directly compare the two drugs for the specific indication of converting new onset AFib RVR 2 3.
• The choice between Amiodarone and Diltiazem should be based on individual patient characteristics and clinical judgment, considering factors such as the presence of underlying heart disease, left ventricular function, and potential side effects.
• Key points to consider:
  • Efficacy in slowing ventricular rate
  • Ability to convert AFib to normal sinus rhythm
  • Potential side effects and interactions
  • Individual patient characteristics and clinical presentation 2 3

From the Research

Comparison of Amiodarone and Diltiazem for Conversion of New Onset AFib RVR

• The study 4 compared the efficacy of diltiazem and amiodarone pretreatment on direct-current conversion of persistent atrial fibrillation.
• The results showed that amiodarone was more effective in determining spontaneous or electric conversion, with a higher success rate (91% vs 76%) and lower recurrence rate at 1 month (28% vs 56%).
• Diltiazem was found to be less effective in determining spontaneous or electric conversion, but was considered a second-choice treatment in patients where amiodarone is contraindicated.

Diltiazem vs Metoprolol for Atrial Fibrillation with Rapid Ventricular Response

• The study 5 compared the effectiveness of intravenous diltiazem and metoprolol in patients with atrial fibrillation and rapid ventricular response, and found that diltiazem effectively controlled heart rate quicker and reduced heart rate by 20% or greater more frequently than metoprolol.
• Another study 6 also found that diltiazem was more effective in achieving rate control in ED patients with atrial fibrillation or flutter, with a more rapid and substantial decrease in heart rate.
• However, the study 7 found that one observational study showed no difference between metoprolol and diltiazem for successful rate control, but worsening heart failure symptoms occurred more frequently in those receiving diltiazem.

Management of Atrial Fibrillation with Rapid Ventricular Response

• The study 8 evaluated key evidence-based updates concerning atrial fibrillation with rapid ventricular response, and found that rate or rhythm control should be pursued in hemodynamically stable patients, and that anticoagulation is an important component of management.
• The study 7 also found that high-level evidence to inform clinical decision making regarding effective and safe management of atrial fibrillation with rapid ventricular response in patients with acute decompensated heart failure is lacking.