Why give amiodarone (Amio) in ventricular fibrillation (VFib)?

From the Guidelines

Amiodarone should be given in ventricular fibrillation (VFib) as a second-line antiarrhythmic medication after defibrillation attempts have failed, with a recommended dose of 300 mg IV push for the first dose, followed by a second dose of 150 mg if VFib persists, as it has been shown to improve survival and hospital admission rates in patients with shock-resistant VFib 1.

Key Points

• Amiodarone works by blocking multiple ion channels (sodium, potassium, and calcium) and has alpha and beta-blocking properties, which helps stabilize cardiac cell membranes and suppress abnormal electrical activity.
• The medication is used to increase the likelihood of successful defibrillation and to prevent recurrence of VFib after a successful shock.
• Side effects include hypotension and bradycardia, so blood pressure monitoring is essential after return of spontaneous circulation.
• According to the 2018 American Heart Association focused update on advanced cardiovascular life support, amiodarone or lidocaine can be considered for shock-refractory VF/pVT, with no significant difference in long-term survival or survival with good neurological outcome 1.

Administration and Monitoring

• Amiodarone should only be administered after initial defibrillation attempts and high-quality CPR, as electrical cardioversion remains the definitive treatment for VFib.
• The optimal sequence of ACLS interventions for VF/pVT cardiac arrest, including administration of a vasopressor or antiarrhythmic drug, and the timing of medication administration in relation to shock delivery are not known, and may vary depending on the number of providers participating in the resuscitation, their skill levels, and the ability to secure intravenous/intraosseous access in a timely manner 1.
• It is essential to monitor patients closely for potential adverse effects, such as hypotension and bradycardia, and to adjust the treatment plan accordingly.

From the FDA Drug Label

Amiodarone hydrochloride injection is indicated for initiation of treatment and prophylaxis of frequently recurring ventricular fibrillation (VF) and hemodynamically unstable ventricular tachycardia (VT) in patients refractory to other therapy.

Amiodarone is given in VFib because it is indicated for the initiation of treatment and prophylaxis of frequently recurring ventricular fibrillation (VF) in patients refractory to other therapy 2.

• The drug works by prolonging the cardiac action potential and refractoriness, which helps to stabilize the heart rhythm.
• It is used when other treatments have failed, and its use is recommended for a limited period, typically 48 to 96 hours, until the patient's ventricular arrhythmias are stabilized.

From the Research

Rationale for Amiodarone Use in VFIB

• Amiodarone is used in the treatment of ventricular fibrillation (VFIB) due to its effectiveness in increasing survival rates to hospital admission compared to lidocaine, as shown in a study published in The New England Journal of Medicine 3.
• The study found that 22.8% of patients treated with amiodarone survived to hospital admission, compared to 12.0% of patients treated with lidocaine.
• Another study published in Current Opinion in Critical Care discussed the optimal antiarrhythmic drug therapy for VFIB and found that amiodarone may be beneficial in patients with witnessed arrest, but there is no clear survival benefit for any one particular drug 4.

Comparison with Lidocaine

• A study published in The Heart Surgery Forum compared the effect of lidocaine and amiodarone on preventing ventricular fibrillation in patients undergoing coronary artery bypass grafting and found that both drugs were effective, but amiodarone reduced the need for electrical defibrillation 5.
• However, another study published in the European Journal of Anaesthesiology found that lidocaine was more effective than amiodarone in preventing ventricular fibrillation after release of aortic cross-clamp 6.
• A more recent study published in Chest found that lidocaine was associated with higher odds of return of spontaneous circulation, 24-hour survival, survival to hospital discharge, and favorable neurologic outcome compared to amiodarone in adult patients with in-hospital cardiac arrest from VT/VF 7.

Clinical Considerations

• The choice of antiarrhythmic drug for VFIB may depend on various factors, including the patient's condition, the availability of the drug, and the cost.
• The American Heart Association Advanced Cardiac Life Support (ACLS) guidelines support the use of either amiodarone or lidocaine for cardiac arrest caused by ventricular tachycardia or ventricular fibrillation (VT/VF) 7.
• Further research is needed to determine the optimal antiarrhythmic drug therapy for VFIB and to compare the effectiveness of amiodarone and lidocaine in different patient populations.