Mitral stenosis is a narrowing of the mitral valve, which controls blood flow from the left atrium to the left ventricle. When the valve opening is narrowed, blood flow from the lungs into the left heart is restricted, causing pressure to rise progressively in the left atrium and the pulmonary circulation.
The most common cause worldwide is rheumatic heart disease, in which repeated episodes of rheumatic fever cause inflammation and progressive scarring of the valve leaflets, which eventually thicken, fuse, and calcify. Rheumatic mitral stenosis is now relatively uncommon in the UK due to antibiotic treatment of streptococcal throat infections. Less common causes include congenital mitral stenosis and calcific degeneration in elderly patients.
Symptoms develop gradually and include breathlessness on exertion, fatigue, and atrial fibrillation (which occurs as the left atrium enlarges). In severe cases, pulmonary hypertension and right heart failure can develop. Diagnosis is confirmed by echocardiography, which measures the valve area and pressure gradients; a characteristic mid-diastolic murmur is heard on clinical examination.
Treatment depends on severity. Medical management includes diuretics for fluid overload, anticoagulation for atrial fibrillation, and rate control. Definitive treatment to relieve the obstruction includes percutaneous balloon mitral valvuloplasty (inflating a balloon across the valve to widen it) or surgical mitral valve repair or replacement for more severely deformed valves.
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