## Pathological Features of Rheumatic Heart Disease ### Valve Involvement Hierarchy **Key Point:** The mitral valve is the MOST commonly affected valve in rheumatic heart disease (RHD), followed by the aortic valve. The tricuspid and pulmonary valves are rarely involved. | Valve | Frequency | Lesion Type | | --- | --- | --- | | Mitral | 70–80% | Stenosis > regurgitation | | Aortic | 20–30% | Regurgitation > stenosis | | Tricuspid | 5–10% | Usually secondary to RV dilatation | | Pulmonary | <1% | Rare, usually secondary | ### Pathological Changes in Mitral Stenosis 1. **Commissural Fusion** — leaflets fuse at the commissures, restricting opening; this is the hallmark of mitral stenosis. 2. **Chordae Tendinae** — undergo shortening, thickening, and fusion, preventing leaflet separation. 3. **Leaflet Changes** — thickening, calcification, and fibrosis; leaflets become rigid and immobile. 4. **Aschoff Bodies** — granulomatous lesions with central fibrinoid necrosis surrounded by Anitschkow cells and Aschoff giant cells; seen in acute rheumatic fever. ### Acute vs. Chronic Phase **High-Yield:** - **Acute phase**: Macrophage infiltration, Aschoff bodies, myocarditis, endocarditis, pericarditis. - **Chronic phase**: Fibrosis, calcification, commissural fusion, stenosis/regurgitation. **Clinical Pearl:** The progression from acute rheumatic fever to chronic RHD takes years; repeated streptococcal infections accelerate valve damage. **Warning:** Do NOT confuse the sequence — acute inflammation precedes chronic fibrosis. Aschoff bodies are seen in the acute phase, NOT in chronic stenotic mitral valve. ### Why Option 2 is Correct The aortic valve is involved in only 20–30% of RHD cases and is NEVER the primary or most common valve affected. The mitral valve is affected in 70–80% of cases. This statement is **FALSE** and is the correct answer to an "EXCEPT" question. [cite:Robbins 10e Ch 12]
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