## Most Common Cause of Mitral Stenosis in India **Key Point:** Rheumatic heart disease (RHD) is the most common cause of mitral stenosis globally and particularly in India, accounting for >90% of cases in developing nations. ### Pathophysiology of RHD-Induced Mitral Stenosis 1. **Acute rheumatic fever (ARF)** follows Group A Streptococcal pharyngitis 2. **Molecular mimicry** triggers cross-reactive antibodies against cardiac myosin 3. **Acute carditis** causes mitral valve inflammation and edema 4. **Chronic fibrosis and calcification** lead to valve leaflet thickening, commissural fusion, and chordal shortening 5. **Progressive stenosis** develops over years to decades ### Why RHD Dominates in India | Factor | Impact | |--------|--------| | High streptococcal infection burden | Repeated ARF episodes | | Delayed/inadequate antibiotic prophylaxis | Progression to chronic RHD | | Poor socioeconomic conditions | Crowding, malnutrition, limited healthcare access | | Genetic susceptibility | Higher prevalence of HLA-DR3 and HLA-DQ2 | **High-Yield:** Mitral stenosis is the most common single valvular lesion in RHD; mitral regurgitation is the most common overall lesion (can occur alone or with stenosis). **Clinical Pearl:** The diastolic murmur at the apex with patient in left lateral decubitus position is the classic finding for mitral stenosis. Opening snap (if valve still mobile) precedes the murmur. ### Epidemiology - **Prevalence in India:** RHD affects 5–10 per 1000 population in rural areas - **Age of presentation:** Typically 20–50 years; women > men (2:1) - **Time to symptomatic stenosis:** 10–20 years after initial ARF **Mnemonic: RHD Valve Involvement (in order of frequency)** — **M-A-T-P** (Mitral > Aortic > Tricuspid > Pulmonary). Mitral stenosis alone occurs in ~25% of RHD; combined mitral stenosis + regurgitation in ~65%.
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