31. Mitral valve stenosis

Definition:

• Mitral stenosis is the narrowing of the mitral valve orifice, normally 3–6 cm².
• Clinically significant if < 1.5 cm².
• Can be congenital or more commonly acquired.

Etiology:

• Rheumatic fever (most common cause)
• Congenital malformations (less common)

Pathophysiology:

1. Narrowed mitral valve restricts blood flow from LA to LV during diastole.
2. ↑ LA pressure to push blood into LV → LA hypertrophy then dilatation
3. Blood backs up into pulmonary veins → ↑ pulmonary venous pressure → pulmonary congestion and edema
4. Pulmonary HTN develops due to chronic back pressure → RV pressure overload → RV hypertrophy → RV failure
5. Stretched LA → increased irritability of atrial conduction system → Atrial fibrillation
6. Stagnant flow in dilated LA → thrombus formation → embolism risk
7. Staging:

• Stage I: LA hypertrophy, mild pulmonary congestion
• Stage II: Pulmonary hypertension, RV and RA dilatation, systemic venous congestion (right heart failure signs)

Symptoms:

• Dyspnea on exertion
• Orthopnea, PND (paroxysmal nocturnal dyspnea)
• Fatigue
• Peripheral cyanosis
• Palpitations (especially with AF)

• Hemoptysis (from ruptured bronchial veins)
• Thromboembolic events (e.g., stroke)
• Ascites and peripheral edema (late, due to RHF)
• Angina (occasionally)