A 28-year-old woman with a history of acute rheumatic fever presents with mitral stenosis and atrial fibrillation. She is haemodynamically stable with a ventricular rate of 110 bpm. What is the drug of choice for rate control in this patient?

Explanation

## Rate Control in Rheumatic Heart Disease with Atrial Fibrillation ### Clinical Context In a haemodynamically stable patient with rheumatic heart disease (RHD), mitral stenosis, and atrial fibrillation (AF) with a ventricular rate of 110 bpm, rate control is the immediate priority. The choice of agent depends on haemodynamic status, ventricular function, and the presence of structural cardiac disease. ### Why Beta-Blockers Are Preferred **Key Point:** In haemodynamically stable AF — including AF complicating RHD with mitral stenosis — beta-blockers (e.g., metoprolol) are the **first-line agents for rate control** per current ESC (2020) and ACC/AHA guidelines, provided there is no overt decompensated heart failure or severe bronchospasm. **High-Yield:** Beta-blockers achieve rate control by: 1. **Slowing AV nodal conduction** — reducing ventricular rate effectively at rest AND during exertion 2. **Blunting sympathetic activation** — particularly important in mitral stenosis, where tachycardia dramatically shortens diastolic filling time and raises left atrial pressure ### Why Digoxin Is NOT First-Line Here Digoxin was historically favoured in RHD-AF, but modern evidence and guidelines have downgraded it to **second-line** status: - Digoxin controls rate **at rest** but is ineffective during exercise/sympathetic activation - It has a **narrow therapeutic index** with significant toxicity risk - It provides **no mortality benefit** in AF (AFFIRM trial data) - It is reserved for patients with **reduced EF / decompensated heart failure** where beta-blockers and CCBs are contraindicated ### Comparison with Alternatives | Agent | Role in RHD-AF | Notes | |-------|---------------|-------| | **Beta-blocker (metoprolol)** | **First-line** (haemodynamically stable) | Effective at rest and exertion; well-tolerated | | **Diltiazem / Verapamil** | Alternative first-line (if beta-blocker contraindicated) | Avoid if EF reduced | | **Digoxin** | Second-line / adjunct | Use if HF with reduced EF; poor exercise rate control | ### Clinical Pearl **In mitral stenosis with AF**, tachycardia is particularly harmful because it reduces diastolic filling time, worsening the gradient across the stenotic valve and precipitating pulmonary oedema. Beta-blockers are ideal because they control rate both at rest and on exertion, unlike digoxin which fails during sympathetic surges. **Reference:** ESC Guidelines for the Diagnosis and Management of Atrial Fibrillation (2020); Harrison's Principles of Internal Medicine, 21e, Ch. 236 & 297; Braunwald's Heart Disease, 12e. **Mnemonic:** **BEST Rate Control in Stable AF** = **B**eta-blocker **E**ffective at rest and **S**tress, **T**itrate to heart rate < 110 bpm.