Mitral valve disease

The mitral valve is on the left-hand side of the heart between the left atrium and the left ventricle. The valve may become damaged or diseased, which prevents the valve from working properly and so causes stenosis or regurgitation.

Mitral stenosis is a narrowing of the mitral valve. It stops the valve from opening properly, and this will obstruct the flow of blood from the left atrium into the left ventricle. As the narrowing of the valve becomes more severe, the flow of blood back into the left atrium puts strain and pressure on it and it struggles to pump blood into the left ventricle. This rise in pressure causes the wall of the left atrium to become thickened and enlarged. The enlargement of the left atrium can cause atrial fibrillation, an abnormal heart rhythm.

Mitral stenosis is nearly always caused by:

• Rheumatic fever and rheumatic heart disease; or
• Hardening of the valve as a result of a build-up of calcium.

Both of these cause the valve leaflets and the area that holds it in position, to thicken and become rigid. This prevents the leaflets from opening properly and so the blood cannot flow freely from the left atrium to the left ventricle.

When the valve is only mildly affected by stenosis there may be no symptoms or very few symptoms. As the disease progresses the following symptoms may arise.

• Shortness of breath when active
• Palpitations or an irregular heartbeat
• Fainting or dizziness
• Chest pain or angina