A 65-year-old woman with atrial fibrillation (AF) and a rapid ventricular response (HR 120 bpm) presents to the emergency department. She is haemodynamically stable. Which drug is the first-line choice for acute rate control in this patient?

Question

Accepted Answer

C. Intravenous verapamil. ## Acute Rate Control in Atrial Fibrillation

**Key Point:** Intravenous verapamil is the first-line agent for acute rate control in haemodynamically stable AF because it rapidly slows AV nodal conduction and has a quick onset (1–5 minutes IV).

### Mechanism of Action
- Non-dihydropyridine calcium channel blocker
- Blocks L-type calcium channels in the AV node
- Increases AV nodal refractoriness and slows conduction velocity
- Reduces ventricular rate without converting AF rhythm

### Comparison of Rate-Control Agents in Acute AF

| Agent | Route | Onset | Duration | Haemodynamic Effect | First-Line? |
|---|---|---|---|---|---|
| Verapamil | IV | 1–5 min | 30–60 min | Mild ↓BP, ↓CO | **Yes** (stable) |
| Diltiazem | IV | 2–7 min | 30–60 min | Mild ↓BP, ↓CO | Yes (alternative) |
| Digoxin | IV | 30–60 min | 4–6 hrs | Minimal ↓BP | No (slow onset) |
| Amiodarone | IV | 5–10 min | Hours | ↓BP, ↓CO | No (rhythm control) |
| Beta-blocker | IV | 5–15 min | Variable | ↓HR, ↓BP, ↓CO | Yes (if no contraindication) |

**High-Yield:** In **haemodynamically stable** AF, the first-line agents are IV verapamil, IV diltiazem, or IV beta-blocker (e.g., metoprolol). In **haemodynamically unstable** AF, use synchronized DC cardioversion or IV amiodarone.

**Clinical Pearl:** Verapamil is contraindicated in AF with pre-excitation (e.g., Wolff–Parkinson–White syndrome) because it blocks the AV node and may preferentially conduct through the accessory pathway, causing dangerously rapid ventricular rates.

**Mnemonic:** **VERAPAMIL for VENTRICULAR rate control** — the V's match. Remember: verapamil slows the AV node, not the atrial rate.

**Tip:** NEET PG often tests the distinction between rate control (verapamil, diltiazem, beta-blockers) and rhythm control (amiodarone, flecainide). In acute stable AF, rate control is the priority.

Answer

A. Oral diltiazem

Answer

B. Intravenous amiodarone

Answer

D. Intravenous digoxin

A 65-year-old woman with atrial fibrillation (AF) and a rapid ventricular response (HR 120 bpm) presents to the emergency department. She is haemodynamically stable. Which drug is the first-line choice for acute rate control in this patient?

Explanation

Acute Rate Control in Atrial Fibrillation

Mechanism of Action

Comparison of Rate-Control Agents in Acute AF

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Agent	Route	Onset	Duration	Haemodynamic Effect	First-Line?
Verapamil	IV	1–5 min	30–60 min	Mild ↓BP, ↓CO	Yes (stable)
Diltiazem	IV	2–7 min	30–60 min	Mild ↓BP, ↓CO	Yes (alternative)
Digoxin	IV	30–60 min	4–6 hrs	Minimal ↓BP	No (slow onset)
Amiodarone	IV	5–10 min	Hours	↓BP, ↓CO	No (rhythm control)
Beta-blocker	IV	5–15 min	Variable	↓HR, ↓BP, ↓CO	Yes (if no contraindication)