What is the role of amiodarone in managing polymorphic ventricular tachycardia that is not torsades de pointes?

From the Guidelines

Amiodarone is a recommended treatment for polymorphic ventricular tachycardia (PMVT) that is not torsades de pointes, particularly when the arrhythmia is refractory to other treatments, with an initial IV/IO dose of 300 mg, followed by a second IV/IO dose of 150 mg if required, as supported by the 2018 American Heart Association focused update on advanced cardiovascular life support 1.

Key Considerations

• The use of amiodarone in PMVT is based on its ability to block multiple ion channels and its beta and alpha-adrenergic blocking properties, making it effective for various arrhythmias.
• However, amiodarone is contraindicated in torsades de pointes as it can prolong the QT interval and potentially worsen this specific type of arrhythmia.
• Patients on amiodarone require regular monitoring for potential side effects, including thyroid dysfunction, pulmonary toxicity, liver abnormalities, and corneal deposits, especially during long-term therapy.

Administration and Dosage

• For acute management, amiodarone should be administered intravenously with a loading dose of 300 mg, followed by a second dose of 150 mg if required, as recommended by the 2018 American Heart Association guidelines 1.
• The captisol-based formulation of amiodarone is currently marketed only as a premixed infusion, not in concentrated form, making it impractical for rapid administration during cardiac arrest, whereas the polysorbate-based formulation is available in concentrated form for rapid administration.

Clinical Context

• The 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death recommends the use of amiodarone in patients with polymorphic VT or VF with ST-elevation MI, with a Class I recommendation and Level of Evidence B-NR 1.
• The 2015 ESC guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death recommend the use of amiodarone (150–300 mg i.v. bolus) to acutely suppress recurrent haemodynamically relevant VAs, including polymorphic VT 1.

From the Research

Role of Amiodarone in Polymorphic Ventricular Tachycardia

Amiodarone can be considered for managing polymorphic ventricular tachycardia that is not torsades de pointes, especially after the third shock during cardiac arrest or in stable patients with polymorphic tachycardia 2, 3.

Efficacy of Amiodarone

• Amiodarone has been shown to be effective in treating ventricular tachycardia or ventricular fibrillation refractory to conventional antiarrhythmic drugs, with 69% of patients having no recurrence of symptomatic VT or VF over a follow-up period 2.
• In patients with post-myocardial infarction polymorphous ventricular tachycardia, amiodarone was effective in suppressing the arrhythmia in four patients who were unresponsive to lidocaine, procainamide, or bretylium 3.
• However, amiodarone is poorly effective for the acute termination of sustained monomorphic ventricular tachycardia, with a success rate of only 29% 4.

Safety and Contraindications

• Amiodarone can cause significant toxicity, with adverse effects occurring in 51% of patients, including tremor, nausea, visual halos, thyroid function abnormalities, and pulmonary interstitial infiltrates 2.
• Amiodarone is contraindicated in patients with congenital long QT syndrome, as it may exacerbate the ventricular arrhythmia 5.
• The role of amiodarone in managing polymorphic ventricular tachycardia can be quite different depending on the specific form of the arrhythmia, and each case requires individualized therapeutic approach 6.