A 52-year-old man with a history of hypertension and left ventricular hypertrophy presents with symptomatic atrial fibrillation of 3 days' duration. His blood pressure is 145/92 mmHg, heart rate 110 bpm, and echocardiography shows preserved ejection fraction. He has no structural heart disease. Which drug is the preferred first-line agent for rate control in this patient?

Explanation

## First-Line Rate Control in Atrial Fibrillation **Key Point:** In patients with atrial fibrillation and preserved ejection fraction (EF ≥40%), non-dihydropyridine calcium channel blockers (diltiazem, verapamil) and beta-blockers are first-line agents for rate control. Diltiazem is preferred in this case because it provides both rate control and has mild negative inotropic effects without the systemic effects of beta-blockers in a hypertensive patient. ### Why Diltiazem is Optimal Here 1. **Mechanism of rate control:** Diltiazem slows AV nodal conduction by blocking L-type calcium channels, increasing the AV nodal refractory period and reducing ventricular rate. 2. **Hemodynamic profile:** Maintains cardiac output better than verapamil; has modest blood pressure-lowering effect (beneficial in this hypertensive patient). 3. **No structural contraindication:** Safe in preserved EF; can be used even with LVH. 4. **Rapid onset:** Effective for acute rate control (IV or oral loading available). ### Comparison with Other Agents | Agent | Class | Rate Control | EF ≥40% Safety | Use Case | |-------|-------|--------------|----------------|----------| | **Diltiazem** | Non-DHP CCB | ✓ Excellent | ✓ Safe | **First-line in preserved EF** | | Verapamil | Non-DHP CCB | ✓ Excellent | ✓ Safe | Alternative to diltiazem | | Beta-blocker | Class II | ✓ Excellent | ✓ Safe | First-line if concurrent CAD/MI | | Flecainide | Class IC | ✗ No rate control | ✗ Contraindicated | Only for rhythm control; proarrhythmic in structural disease | | Sotalol | Class III | ✓ Moderate | ⚠ Caution | Requires QT monitoring; second-line | | Digoxin | Vagomimetic | ✓ Modest | ✓ Safe | Limited efficacy; reserved for sedentary patients or HF | **High-Yield:** Beta-blockers (metoprolol, atenolol) are equally acceptable first-line alternatives if the patient has concurrent CAD, post-MI status, or symptomatic heart failure. However, diltiazem is preferred in pure hypertension with AF and preserved EF because it does not cause fatigue or sexual dysfunction. **Clinical Pearl:** In acute AF with hemodynamic compromise, IV diltiazem (0.25 mg/kg bolus) achieves rate control within 2–5 minutes. For chronic management, oral diltiazem 120–360 mg/day in divided doses is standard. **Warning:** Flecainide is a Class IC antiarrhythmic that does NOT control ventricular rate in AF (it is a rhythm-control agent, not a rate-control agent) and is contraindicated in structural heart disease due to proarrhythmic risk (CAST trial).