A 72-year-old woman with chronic atrial fibrillation and a ventricular rate of 110 bpm presents with dyspnoea and fatigue. Her ECG shows irregular RR intervals and a normal QRS duration. She has normal renal function and no signs of heart failure. Which is the drug of choice for acute rate control in this patient?

Question

Accepted Answer

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

**Key Point:** Intravenous verapamil (or diltiazem) is the first-line drug of choice for acute rate control in haemodynamically stable patients with atrial fibrillation and a rapid ventricular response.

### Mechanism of Action

Verapamil is a non-dihydropyridine calcium channel blocker that:
1. Slows AV nodal conduction by blocking L-type calcium channels
2. Increases the AV nodal refractory period
3. Reduces the ventricular rate by preventing rapid AV nodal transmission of atrial impulses
4. Works within 2–5 minutes when given intravenously

### Comparison of Rate-Control Agents

| Drug | Onset | Route | Advantages | Disadvantages | Use in AF |
|------|-------|-------|-----------|---------------|----------|
| **IV Verapamil** | 2–5 min | IV | Rapid, effective, safe in stable patients | Avoid in hypotension, LV dysfunction | **First-line** |
| **IV Diltiazem** | 2–7 min | IV | Similar to verapamil; less negative inotrope | Similar contraindications | **Alternative** |
| **IV Amiodarone** | 15–30 min | IV | Works in unstable patients, converts rhythm | Slow onset; proarrhythmic; hypotension | Unstable/refractory |
| **Digoxin** | 30–60 min | IV/oral | Oral maintenance; inotropic support | Slow onset; narrow therapeutic index; drug interactions | Chronic/HF |
| **Sotalol** | Hours | Oral | Antiarrhythmic + rate control | Prolongs QT; bradycardia risk; oral only | Not acute |

**High-Yield:** In acute AF with rapid ventricular response in a **haemodynamically stable** patient, IV calcium channel blockers (verapamil or diltiazem) are preferred over IV amiodarone because they work faster and have fewer side effects.

**Clinical Pearl:** Amiodarone is reserved for:
- Haemodynamically **unstable** patients (hypotensive, pulmonary oedema, shock)
- Patients with **contraindications** to calcium channel blockers (severe LV dysfunction, cardiogenic shock)
- Refractory AF despite other agents

**Warning:** Do NOT use verapamil or diltiazem in patients with:
- Severe hypotension
- Acute decompensated heart failure with reduced ejection fraction (HFrEF)
- Pre-excitation syndromes (e.g. Wolff–Parkinson–White) — risk of accelerated conduction via accessory pathway

### Clinical Decision Algorithm

```mermaid
flowchart TD
  A[Atrial Fibrillation with RVR]:::outcome --> B{Haemodynamically stable?}:::decision
  B -->|Yes| C{LV dysfunction or HF?}:::decision
  B -->|No| D[IV Amiodarone]:::action
  C -->|No| E[IV Verapamil or Diltiazem]:::action
  C -->|Yes| F[IV Amiodarone or IV Digoxin]:::action
  E --> G[Rate control achieved]:::outcome
  F --> G
  D --> G
```

### Dosing

- **IV Verapamil:** 5 mg IV bolus over 2 minutes; repeat 10 mg after 15–30 minutes if needed (max 20 mg)
- **IV Diltiazem:** 0.25 mg/kg IV bolus over 2 minutes; repeat 0.35 mg/kg after 15 minutes if needed
- **IV Amiodarone:** 150 mg IV over 10 minutes, then infusion
- **IV Digoxin:** 0.5 mg IV, then 0.25 mg every 6 hours (max 1.5 mg in 24 hours)

Answer

A. Intravenous amiodarone

Answer

B. Sotalol

Answer

C. Digoxin

Explanation

Acute Rate Control in Atrial Fibrillation

Mechanism of Action

Comparison of Rate-Control Agents

Clinical Decision Algorithm

Dosing

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