## Valve Involvement in Rheumatic Heart Disease **Key Point:** The mitral valve is the most commonly affected valve in rheumatic heart disease (RHD), accounting for approximately 65–70% of all cases. ### Frequency of Valve Involvement | Valve | Frequency | Pattern | |-------|-----------|----------| | Mitral | 65–70% | Stenosis > Regurgitation | | Aortic | 30% | Regurgitation > Stenosis | | Tricuspid | 10% | Usually secondary to RV dilatation | | Pulmonary | <1% | Extremely rare | **High-Yield:** Mitral stenosis is the single most common lesion in RHD globally, particularly in developing countries where acute rheumatic fever (ARF) is endemic. ### Why Mitral Valve? 1. **Highest pressure gradient** — The mitral valve experiences the highest closing pressure during ventricular systole, making it most susceptible to inflammatory damage. 2. **Anatomical vulnerability** — The mitral apparatus is exposed to maximum turbulent flow during the cardiac cycle. 3. **Pathophysiology** — Post-streptococcal autoimmunity (molecular mimicry between Group A Streptococcus M protein and cardiac myosin) preferentially damages mitral leaflets. **Clinical Pearl:** In RHD, mitral stenosis typically develops first, followed by aortic valve involvement. Isolated aortic stenosis from RHD is rare; when aortic disease occurs, it is usually aortic regurgitation. **Mnemonic:** **MAT** — **M**itral most common, **A**ortic second, **T**ricuspid rare (in RHD).
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