Mitral Stenosis

The mitral valve is a heart valve that lies between the left atrium and left ventricle. The valve has two flaps (cusps). The valve allows blood to flow into the left ventricle when the left atrium squeezes (contracts). When the left ventricle contracts, the valve closes and the blood flows out through the aortic valve into the aorta. (The aorta is the main artery which takes blood to the body.)

The cusps are stopped from turning inside out by thin strands of tissue called chordae. The chordae anchor the cusps to the inside wall of the ventricle. The valve or chordae may get damaged or scarred which can prevent the valve from working properly. This can lead to disorders called mitral stenosis, mitral regurgitation, or both. 

Mitral stenosis means that when the mitral valve opens, it does not open fully. The opening is therefore narrower than normal (stenosed). So, there is some restriction of blood flow from the left atrium to the left ventricle. This in turn means there is a reduced amount of blood that is pumped out into the body from the left ventricle. In general, the more narrowed the valve, the less blood can get through and the more severe the problem is likely to be.

Symptoms

If the valve is only mildly narrowed (stenosed) you may have no symptoms or problems. If the stenosis is more severe, the symptoms may include:

• Shortness of breath, especially with activity or when you lie down
  
• Tiredness
  
• Swollen ankles (oedema)
  
• Heart palpitations
  
• Dizziness or fainting
  
• Coughing up blood (haemoptysis)
  
• Chest pain (angina)

Treatment

Medication

Mild cases may not require any regular medication. Although medicines cannot correct a narrowed (stenosed) mitral valve, some medicines may be prescribed to help ease symptoms, or to help prevent complications - for example, angiotensin-converting enzyme (ACE) inhibitors, 'water tablets' (diuretics) and anticoagulation medication. If you develop atrial fibrillation, several medicines can be used to slow the heart rate down.

Surgical treatment

Surgical treatment is needed in more severe cases. There are various options, depending of the exact site and severity of the stenosis.

Stretching the stenosed valve
This is a procedure that does not involve open heart surgery. It is called percutaneous balloon commissurotomy or balloon valvuloplasty. (It is called a commissurotomy, as the area where the valve flaps (cusps) come into contact with each other are known as the commissures.)

It is done by inserting a thin tube called a catheter through the skin (percutaneous) into the main blood vessel in the top of the leg. The catheter is passed up to the heart. The tip of the catheter is placed in the mitral valve opening. A balloon at the tip of the catheter is then inflated to stretch the narrowed valve. This is often successful in widening the narrowed valve.

Valve repair is possible in some cases
This is called mitral commissurotomy or mitral valvotomy. This is usually done by open heart surgery. Basically, the edges (commissures) of valve cusps that have become scarred and fused are shaved back to widen the narrowed valve opening.

Valve replacement is needed in some cases
This may be with a mechanical or a tissue valve.

• Mechanical valves are made of materials which are not likely to react with your body (for example, those made from titanium), although they can produce a noise which can be heard outside the body.
• Tissue valves are made from treated animal tissue (for example, valves from a pig).

If you need surgery, a surgeon will advise on which is the best option for your situation.

What is the outlook for people with mitral stenosis?

In some cases, the disorder is mild and causes no symptoms. If you develop symptoms they tend to become gradually worse over the years. However, the speed of decline can vary. It often takes years for symptoms to become serious. Medication can ease symptoms but cannot reverse a narrowed (stenosed) valve.

Surgical treatments have greatly improved the outlook (prognosis) for most people with more severe stenosis. Surgery has a very good success rate. However, as with all surgical procedures and operations, there is some risk involved when you have surgery. Complications due to surgery occur in a small number of cases.