Mitral stenosis describes the obstruction of blood flow across the mitral valve from the left atrium to the left ventricle. This leads to increases in pressure within the left atrium, pulmonary vasculature and right side of the heart.

It is said that the causes of mitral stenosis are 'rheumatic fever, rheumatic fever and rheumatic fever'. Rarer causes that may be seen in the exam include mucopolysaccharidoses, carcinoid and endocardial fibroelastosis

Features

• dyspnoea
  • ↑ left atrial pressure → pulmonary venous hypertension
• haemoptysis
  • due to pulmonary pressures and vascular congestion
  • may range from pink frothy sputum to sudden haemorrhage secondary to rupture of thin-walled and dilated bronchial veins
• mid-late diastolic murmur (best heard in expiration)
• loud S1
• opening snap
  • indicates mitral valve leaflets are still mobile
• low volume pulse
• malar flush
• atrial fibrillation
  • secondary to ↑ left atrial pressure → left atrial enlargement

Features of severe MS

• length of murmur increases
• opening snap becomes closer to S2

Chest x-ray

• left atrial enlargement may be seen

Echocardiography

• the normal cross-sectional area of the mitral valve is 4-6 sq cm. A 'tight' mitral stenosis implies a cross-sectional area of < 1 sq cm

Management

• patients with associated atrial fibrillation require anticoagulation
  • currently warfarin is still recommended for patients with moderate/severe MS
  • there is an emerging consensus that direct-acting anticoagulants (DOACs) may be suitable for patients with mild MS who develop atrial fibrillation