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Mitral Stenosis
By peace | June 20, 2008
The mitral valve lies between the left atrium and left ventricle. The valve has two flaps or ‘cusps’. The valve allows blood to flow into the left ventricle when the left atrium 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 (not shown in the diagram) 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. It is narrowed (’stenosed’) when it is open. 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 that can get through, the more severe the problem is likely to be.
Causes
Most often Rheumatic Fever where the heart and valves are inflamed. Rheumatic fever usually affects children and attacks may not always be recognised at the time. A proportion of those afflicted suffer permanent heart damage, most commonly at the mitral valve. There may be a latent period of ten to 20 years before symptoms appear. Stenosis(narrowing) is more often found, but a faulty leaking valve may also have developed. Both conditions may be present.
The most common cause of mitral stenosis is rheumatic fever (RF). Approximately 40% of patients with rheumatic heart disease have isolated mitral stenosis. Conversely, rheumatic involvement is present in 99% of stenotic mitral valves excised at the time of mitral valve replacement. RF, however, is exceedingly rare nowadays. It has been more than 10 years since the Centers for Disease Control and Prevention (CDC) discontinued mandatory reporting of acute RF. Studies in the 1950s during an epidemic on a military base demonstrated a 3% incidence of RF in adults with streptococcal pharyngitis not treated with antibiotics. Studies in children during the same period demonstrated an incidence of only 0.3%.
In children, mitral stenosis may run in families. Signs and symptoms of mitral stenosis include:
- Shortness of breath, especially with physical exertion (exercise) or when the person lies down
- Fatigue, especially during times of increased activity
- Swollen feet or ankles
- Heart palpitations — sensations of a rapid, fluttering heartbeat
- Dizziness or fainting spells
- Frequent respiratory infections, such as bronchitis
- Heavy coughing, sometimes with blood-tinged sputum
- Rarely, chest discomfort or chest pain
Diagnosis and Treatment
Mitral stenosis is a heart valve disorder. Mitral stenosis prevents the valve from opening properly and blocks the blood flow from the left atrium to the left ventricle. As the valve area becomes smaller, less blood flows forward to the body. The atrium swells as pressure builds up and blood may flow back into the lungs, resulting in pulmonary edema (fluid in the lung tissue). Left untreated, mitral stenosis will damage the heart, cause irregular heartbeats and possibly heart failure or other serious complications, including stroke, heart infection, pulmonary edema (water on the lungs) and blood clots.
Doctors make the diagnosis after hearing a characteristic heart murmur through a stethoscope placed over the heart. Overall, the 10-year survival of untreated patients with mitral stenosis is 50-60%, depending on symptoms at presentation. Without surgical intervention, the 20-year mortality is 85%. In untreated patients, the causes of death are as follows:
- Progressive heart failure in 60-70%
- Systemic embolism in 20-30%, pulmonary embolism in 10%
- Infection in 1-5%
Over a period of years the diseased cusps of the valve gradually thicken and fuse. The blood cannot flow forward from the left atrium into the left ventricle, the lungs become congested, and blood vessels within the lungs may bleed.
There are a number of different treatment options. Medications include diuretics (water pills), nitrates, or beta-blockers. Digoxin may be used to treat atrial fibrillation. Anti-coagulants (blood thinners) are used to prevent blood clots from forming and traveling to other parts of the body.
Some patients may need heart surgery to repair or replace the valve. Replacement valves can be made from different materials, some of which may last for decades and others which can wear out and require replacement.
Percutaneous mitral balloon valvotomy (also called valvuloplasty) may be considered instead of surgery. During this procedure, a catheter (tube) is inserted into a vein, usually in the leg, and up into the heart. A balloon on the tip of the catheter is inflated, widening the mitral valve and improving blood flow. This procedure is less likely to work in patients with severely damaged
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