A 62-year-old man with newly diagnosed atrial fibrillation (AF) and no structural heart disease presents to the cardiology clinic. He is haemodynamically stable, has a ventricular rate of 110 bpm, and requires rate control. Which of the following is the drug of choice for rate control in this patient?

Explanation

## Rate Control in Atrial Fibrillation **Key Point:** Beta-blockers (particularly bisoprolol, metoprolol, or atenolol) are the first-line agents for rate control in haemodynamically stable patients with AF and no contraindications. ### Why Beta-Blockers Are First-Line 1. **Mechanism:** Beta-blockers slow AV nodal conduction by blocking β~1~-adrenergic receptors, reducing ventricular rate without affecting atrial activity. 2. **Additional benefits:** Reduce myocardial oxygen demand, lower blood pressure, and provide cardioprotection post-MI. 3. **Safety profile:** Well-tolerated in most patients; effective both at rest and during exercise. ### Comparison of Rate-Control Agents | Agent | Mechanism | First-Line? | Key Limitation | |-------|-----------|-------------|----------------| | **Beta-blockers** (bisoprolol) | AV nodal blockade | Yes | Contraindicated in acute decompensated HF, severe bradycardia | | **Non-dihydropyridine CCBs** (verapamil) | AV nodal blockade | Yes (alternative) | Negative inotrope; avoid in HF | | **Digoxin** | Vagomimetic + AV block | No (2nd/3rd line) | Narrow therapeutic window; ineffective during exercise | | **Amiodarone** | Class I, II, III, IV | No (reserved for rhythm control or refractory cases) | Severe toxicity profile; not for rate control alone | **High-Yield:** In a haemodynamically stable patient with no HF, beta-blockers are preferred over other agents for initial rate control. **Clinical Pearl:** Digoxin is useful only in sedentary patients or those with concurrent HF (positive inotrope), but is inferior to beta-blockers for rate control during exercise. ### Treatment Algorithm ```mermaid flowchart TD A[Atrial Fibrillation - Rate Control Needed]:::outcome --> B{Haemodynamically Stable?}:::decision B -->|Yes| C{Structural Heart Disease or HF?}:::decision B -->|No| D[IV rate-control agent or DC cardioversion]:::urgent C -->|No| E[Beta-blocker or non-DHP CCB]:::action C -->|Yes - HF| F[Digoxin or beta-blocker]:::action C -->|Yes - Other| G[Avoid negative inotropes]:::action E --> H[Bisoprolol, metoprolol, or verapamil]:::outcome ```