A 58-year-old man with chronic atrial fibrillation and a history of myocardial infarction presents for rate control. Which antiarrhythmic drug is the most commonly prescribed for long-term maintenance in this clinical scenario?

Explanation

## Most Common Antiarrhythmic for Chronic AF Rate Control ### Beta-Blockers — Preferred First-Line Agent **Key Point:** Beta-blockers (metoprolol, atenolol, bisoprolol) are the most frequently prescribed antiarrhythmics for chronic atrial fibrillation rate control because they: - Reduce ventricular rate by slowing AV nodal conduction - Provide cardioprotection post-MI (reduce mortality) - Are cost-effective and well-tolerated - Are guideline-recommended first-line for rate control in AF - Have proven mortality benefit in post-MI patients ### Clinical Context: Post-MI AF Management **High-Yield:** In a post-MI patient with AF, beta-blockers offer **dual benefit**: 1. **Rate control** (AV nodal blockade) 2. **Cardioprotection** (reduce ischemic recurrence, arrhythmia risk) This is why beta-blockers are preferred over other rate-control agents in this specific scenario. ### Comparison of Rate-Control Agents in Post-MI AF | Agent | Rate Control | Post-MI Benefit | First-Line? | Common Use | |-------|--------------|-----------------|-------------|------------| | **Beta-blockers** | Excellent | Yes (mortality ↓) | Yes | Most common | | **Verapamil** | Good | No (avoid post-MI) | No | Contraindicated | | **Diltiazem** | Good | Neutral | No | Second-line | | **Amiodarone** | Excellent | Yes (but toxicity) | No | Refractory/unstable | | **Sotalol** | Good | Neutral | No | Alternative if β-blocker failed | **Clinical Pearl:** Verapamil is contraindicated in acute MI and the immediate post-MI period due to negative inotropic effects and risk of cardiogenic shock. This eliminates it as a choice in this patient. **Mnemonic:** **ABCDE for AF rate control** - **A** = Amiodarone (refractory/unstable) - **B** = Beta-blockers (first-line, especially post-MI) - **C** = Calcium channel blockers (verapamil/diltiazem; avoid post-MI) - **D** = Digoxin (elderly, sedentary; now less common) - **E** = Esmolol (acute, short-acting) ### Why Beta-Blockers Are Most Common 1. **Guideline recommendation:** ACC/AHA guidelines list beta-blockers as first-line for rate control in AF. 2. **Post-MI cardioprotection:** Reduce mortality and recurrent ischemia. 3. **Tolerability:** Well-tolerated with minimal drug interactions. 4. **Cost:** Inexpensive and widely available. 5. **Proven efficacy:** Decades of clinical experience and RCT evidence. ### Why Other Agents Are Less Common in This Scenario - **Amiodarone:** Class III agent with broad spectrum; reserved for refractory AF or hemodynamically unstable patients. High toxicity (thyroid, liver, lung, QT prolongation) limits routine use. - **Verapamil:** Contraindicated post-MI due to negative inotropic effects and risk of hemodynamic collapse. - **Sotalol:** Beta-blocker + Class III properties; used if pure beta-blocker fails, but not first-line. [cite:Harrison 21e Ch 226]