## Amiodarone vs. Sotalol: Mechanistic Distinction ### Vaughan-Williams Classification **Key Point:** Amiodarone is a **Class I, II, III, and IV** antiarrhythmic (pan-class agent), while sotalol is a **Class II (beta-blocker) and Class III (potassium channel blocker)** agent. ### Mechanism Comparison | Property | Amiodarone | Sotalol | |----------|-----------|--------| | **Class I (Na+ blockade)** | Yes (mild) | No | | **Class II (β-blockade)** | Yes (mild) | Yes (prominent) | | **Class III (K+ blockade)** | Yes (prominent) | Yes (prominent) | | **Class IV (Ca²⁺ blockade)** | Yes (mild) | No | | **Overall mechanism** | Broad-spectrum | Dual (β + K⁺ channel) | ### Clinical Efficacy in Heart Failure Amiodarone's **multi-channel blockade** makes it superior in reduced ejection fraction (EF ≤35%) because: 1. **Class I effect** → slows conduction, reduces reentry 2. **Class II effect** → reduces sympathetic drive, cardioprotective 3. **Class III effect** → prolongs refractoriness 4. **Class IV effect** → mild negative inotropic effect offset by other benefits Sotalol's **dual mechanism** (Class II + III only) is less effective in severe systolic dysfunction and carries higher risk of torsades de pointes due to QT prolongation without the stabilizing effects of sodium and calcium channel blockade. **High-Yield:** In **reduced EF with AF**, amiodarone is preferred because its **pan-class activity** provides superior rate control and arrhythmia suppression. Sotalol is relatively contraindicated due to increased proarrhythmic risk (torsades) in this population. **Clinical Pearl:** The patient's EF of 35% is the key clinical clue. Amiodarone is the drug of choice for AF in systolic heart failure; sotalol increases mortality in this setting (CAST-like risk).
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