## Anticoagulation in Mitral Stenosis with Atrial Fibrillation **Key Point:** Warfarin (vitamin K antagonist) is the gold standard anticoagulant for stroke prevention in patients with rheumatic mitral stenosis and atrial fibrillation. Direct oral anticoagulants (DOACs) are NOT recommended in this setting. ### Why Warfarin? 1. **Mechanism of benefit:** Warfarin inhibits vitamin K-dependent clotting factors (II, VII, IX, X), reducing thromboembolic risk in the setting of atrial fibrillation and mechanical obstruction. 2. **Evidence base:** Multiple guidelines (ESC, ACC/AHA) recommend warfarin as the preferred agent for rheumatic AF with mitral stenosis because DOACs have not been adequately studied in this high-risk population. 3. **Target INR:** 2–3 for non-valvular AF; some experts recommend 2.5–3.5 for rheumatic mitral stenosis. ### Comparison with Alternatives | Agent | Role in MS + AF | Rationale | |-------|-----------------|----------| | **Warfarin** | First-line | Proven efficacy; extensive data in rheumatic disease | | **Aspirin** | Inadequate | Inferior stroke prevention; reserved for contraindications to anticoagulation | | **Clopidogrel** | Inadequate | Monotherapy inferior to warfarin; no role as single agent | | **DOACs** | Contraindicated | Lack of data in rheumatic MS; not recommended by guidelines | **Clinical Pearl:** Rheumatic mitral stenosis creates a hypercoagulable state due to left atrial enlargement, blood stasis, and endothelial injury—warfarin's broad anticoagulant effect is essential. **High-Yield:** DOACs (apixaban, dabigatran, rivaroxaban) are NOT approved for use in patients with moderate-to-severe rheumatic mitral stenosis, even if in AF. This is a high-yield exam point. **Warning:** Do not confuse rheumatic mitral stenosis (warfarin required) with non-rheumatic AF (where DOACs are acceptable). The presence of structural rheumatic valve disease mandates warfarin.
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