A 52-year-old man from rural India presents with progressive dyspnea on exertion and orthopnea for 6 months. On examination, he has an opening snap followed by a low-pitched diastolic murmur at the apex. Chest X-ray shows pulmonary congestion and straightening of the left heart border. What is the most common cause of this valvular lesion in India?

## Mitral Stenosis: Most Common Cause in India ### Clinical Presentation Recognition The opening snap followed by a low-pitched diastolic murmur at the apex is pathognomonic for **mitral stenosis**. The patient's presentation with dyspnea, orthopnea, and pulmonary congestion confirms hemodynamically significant stenosis. ### Epidemiology in India **Key Point:** Rheumatic heart disease (RHD) remains the most common cause of mitral stenosis globally and particularly in India, despite declining incidence in developed nations. **High-Yield:** In India, RHD accounts for >80% of mitral stenosis cases. This is due to: - High prevalence of acute rheumatic fever (ARF) from Group A Streptococcal infections - Limited access to antibiotics in rural areas - Recurrent streptococcal pharyngitis without prophylaxis - Poor socioeconomic conditions and overcrowding ### Why RHD Causes Mitral Stenosis Rheumatic fever leads to: 1. Acute pancarditis with valve inflammation 2. Valve scarring and fibrosis (chronic phase) 3. Commissural fusion and leaflet thickening 4. Progressive narrowing of the mitral orifice ### Comparison of Mitral Stenosis Etiologies | Cause | Geography | Age at Onset | Associated Features | |-------|-----------|-------------|---------------------| | **Rheumatic heart disease** | India, developing nations | 20–50 years | History of ARF, other valve involvement, AF common | | Degenerative calcific | Developed nations | >60 years | Bicuspid valve, hypertension, hyperlipidemia | | Infective endocarditis | Varies | Any age | Fever, new murmur, emboli, positive blood cultures | | Carcinoid | Rare | 50–70 years | Right-sided lesions, flushing, diarrhea | **Clinical Pearl:** In an Indian patient with mitral stenosis, always assume RHD until proven otherwise. The opening snap is a sign of pliable leaflets (as in RHD); calcified stenotic valves (degenerative) do not produce an opening snap. **Mnemonic — RHD Valve Involvement (Most to Least Common):** **AAMT** - **A**ortic (50%) - **A**ortic + **M**itral (30%) - **M**itral alone (20%) - **T**ricuspid (rare, usually with mitral) ### Diagnostic Confirmation Echocardiography would show: - Restricted leaflet motion - Anterior leaflet thickening - Commissural fusion - Reduced mitral valve area (<1.5 cm²) - Left atrial enlargement - Absence of significant regurgitation (unlike endocarditis) [cite:Harrison 21e Ch 297]