A 58-year-old man with a history of anterior wall myocardial infarction 3 months ago presents with recurrent episodes of sustained ventricular tachycardia (VT). Electrophysiology study confirms re-entrant VT with an ejection fraction of 35%. He is currently on beta-blockers and ACE inhibitors. What is the drug of choice for suppression of this arrhythmia?

Explanation

## Drug of Choice for Sustained VT Post-MI **Key Point:** Amiodarone is the most effective and safest antiarrhythmic agent for suppression of sustained ventricular tachycardia in the setting of structural heart disease (reduced ejection fraction). ### Mechanism and Efficacy Amiodarone is a Class III antiarrhythmic (with properties of all four Vaughan-Williams classes) that: - Prolongs action potential duration and refractory period - Has the lowest proarrhythmic potential among antiarrhythmics - Demonstrates superior efficacy in VT suppression in post-MI patients - Works effectively even in severely reduced ejection fraction (EF ≤35%) ### Why Amiodarone in This Context | Feature | Amiodarone | Flecainide | Sotalol | Procainamide | |---------|-----------|-----------|--------|-------------| | **EF ≤35% safety** | Safe | **Contraindicated** (CAST trial) | Relative caution | Relative caution | | **VT suppression efficacy** | Excellent | Moderate | Moderate | Moderate | | **Proarrhythmic risk** | Lowest | High in structural disease | Moderate | Moderate | | **Post-MI use** | Gold standard | Avoided | Limited | Limited | **High-Yield:** The CAST trial (1989) demonstrated that Class IC antiarrhythmics (flecainide, encainide) increased mortality in post-MI patients with reduced EF despite suppressing arrhythmias — a landmark finding that changed practice. **Clinical Pearl:** Although amiodarone has significant extracardiac toxicity (thyroid, lung, liver), its cardiac safety profile in structural heart disease makes it the preferred agent for sustained VT in reduced EF. Long-term monitoring for toxicity is essential. ### Treatment Algorithm Context ```mermaid flowchart TD A[Sustained VT Post-MI]:::outcome --> B{EF reduced?}:::decision B -->|Yes, EF ≤35%| C[Amiodarone first-line]:::action B -->|No, EF >35%| D[Consider ICD + amiodarone or sotalol]:::action C --> E[ICD placement for secondary prevention]:::action E --> F[Amiodarone as adjunctive therapy]:::action ``` **Citation:** [cite:Harrison 21e Ch 226]