A 32-year-old woman with rheumatic mitral stenosis (MVA 1.2 cm²) presents with palpitations and dyspnea on exertion. She is in sinus rhythm with a heart rate of 92 bpm. Echocardiography confirms moderate-to-severe MS with no left atrial thrombus. What is the drug of choice for rate control and symptom relief in this patient?

Explanation

## Rate Control in Mitral Stenosis **Key Point:** Beta-blockers are the first-line agents for rate control in mitral stenosis with sinus rhythm, as they slow AV nodal conduction and reduce ventricular response without worsening the mitral gradient. ### Mechanism in MS - Beta-blockers decrease heart rate and prolong diastole, allowing more time for blood to cross the stenotic mitral valve - This improves ventricular filling and reduces pulmonary congestion - They also reduce myocardial oxygen demand and provide symptom relief ### Why Beta-Blockers Are Preferred | Agent | Mechanism | Advantage in MS | Disadvantage | |-------|-----------|-----------------|-------------| | **Beta-blocker** | AV nodal block + negative inotropy | Slows rate, improves diastolic filling, reduces symptoms | Mild negative inotropic effect (acceptable in MS) | | Diltiazem | Non-dihydropyridine CCB, AV nodal block | Good rate control | Less predictable; second-line | | Verapamil | Non-dihydropyridine CCB, AV nodal block | Good rate control | Negative inotropic effect; contraindicated if LV dysfunction | | Digoxin | AV nodal block via vagomimetic | Useful in AF with MS | Poor rate control in sinus rhythm; narrow therapeutic index | **High-Yield:** In mitral stenosis, **lengthening diastole is therapeutic** — it allows the stenotic valve more time to open and blood to cross. Beta-blockers achieve this by slowing heart rate and prolonging the PR interval. **Clinical Pearl:** Digoxin is reserved for atrial fibrillation with rapid ventricular response in MS, not for sinus rhythm rate control. Calcium channel blockers (diltiazem, verapamil) are acceptable alternatives but are second-line to beta-blockers in sinus rhythm MS. **Warning:** Dihydropyridine calcium channel blockers (nifedipine, amlodipine) cause reflex tachycardia and are contraindicated in MS — they worsen symptoms by shortening diastole. ### Treatment Algorithm for Symptomatic MS ```mermaid flowchart TD A[Moderate-severe MS + symptoms]:::outcome --> B{Rhythm?}:::decision B -->|Sinus rhythm| C[Beta-blocker]:::action B -->|Atrial fibrillation| D{Rate control needed?}:::decision D -->|Yes| E[Beta-blocker or diltiazem]:::action E --> F{Rate controlled?}:::decision F -->|No| G[Add digoxin]:::action C --> H{Symptom relief?}:::decision H -->|Yes| I[Continue + anticoagulation if AF]:::outcome H -->|No| J[Consider balloon mitral valvotomy or surgery]:::action ``` [cite:Harrison 21e Ch 297]