## Valve Involvement in Rheumatic Heart Disease **Key Point:** The mitral valve is the single 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 regurgitation; rarely stenosis | | Pulmonary | <1% | Extremely rare; isolated involvement | **High-Yield:** Mitral stenosis is the **hallmark lesion** of RHD. The mitral valve bears the highest hemodynamic stress during ventricular systole, making it most vulnerable to rheumatic damage. ### Pathophysiology of Mitral Involvement 1. **Acute phase:** Verrucous vegetations form along the line of valve closure (endocarditis). 2. **Chronic phase:** Fibrosis, calcification, and commissural fusion lead to stenosis. 3. **Hemodynamic stress:** The mitral valve closes against the highest left ventricular pressure, explaining its preferential involvement. **Clinical Pearl:** In RHD, mitral stenosis is often **pure stenosis** (70% of cases), whereas aortic valve disease tends to present as **aortic regurgitation** (not stenosis). This anatomical difference reflects the direction of blood flow and valve closure mechanics. **Mnemonic:** **MAT** — **M**itral (most common), **A**ortic (second), **T**ricuspid (third). Pulmonary valve is essentially never involved in isolation.
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