What Are the Causes of Mitral Stenosis?

Operating theatre In a cardiac surgery ward in Africa.
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Mitral stenosis is an obstruction of the mitral valve, which reduces the flow of blood from the left atrium to the left ventricle. Mitral stenosis is relatively uncommon today in developed countries, but when it occurs it can cause significant cardiac problems.

What Is Mitral Stenosis?

The mitral valve controls the opening between the left atrium and the left ventricle. When the left atrium contracts, the mitral valve opens to allow blood to flow into the left ventricle. The left ventricle then immediately contracts, and the mitral valve closes to prevent the blood from going backwards into the left atrium.

With mitral stenosis, the mitral valve is thickened and immobile (that is, stenotic), and is unable to open fully. When this occurs, the left atrium cannot empty completely. The blood tends to back up, leading to increased left atrial pressures. Over a long period of time, significant heart problems can result.

What Are the Causes of Mitral Stenosis?

Several conditions can produce mitral stenosis:

  • Rheumatic heart disease is the most common cause. Because rheumatic heart disease has become rare in developed countries, mitral stenosis is now seen much less frequently than it was in past decades.
  • Some forms of congenital heart disease can cause mitral stenosis. In these cases, the mitral valve fails to develop normally.
  • Mitral annular calcification (a condition in which calcium deposits form on the mitral valve, usually in association with with aging or kidney disease) can cause mitral stenosis. While mitral annular calcification is a fairly common condition, it more commonly causes mitral regurgitation and only rarely produces mitral stenosis.
  • Infectious endocarditis (infection of the heart valves) can very rarely result in mitral stenosis.

What Problems Does Mitral Stenosis Cause?

In mitral stenosis caused by rheumatic heart disease (the most common cause), the valve problem develops slowly, over a period of years, and symptoms appear gradually. In most cases, the mitral stenosis is first diagnosed 15 to 20 years after rheumatic fever has occurred.

During all this time, the pressure within the left atrium gradually increases, and that chamber eventually becomes enlarged. The increased pressure is also transmitted backwards, to the blood vessels in the lungs, and eventually to the pulmonary artery. Pulmonary artery hypertension, high pressure in the pulmonary artery, often results.

Pulmonary artery hypertension can eventually cause heart failure affecting the right side of the heart. Right-sided heart failure is commonly associated with extreme fatigue and massive fluid accumulation (edema) in the legs, and often in the belly.

Atrial fibrillation is extremely common in people with mitral stenosis. Up to 70% of people with mitral stenosis will eventually develop this arrhythmia.

Thromboembolism is also an issue with mitral stenosis. Blood clots that form within the abnormal left atrium break off and cause tissue damage, especially stroke. This problem is a risk in anybody with atrial fibrillation, but that risk is especially high when the atrial fibrillation is associated with mitral stenosis. In fact, thromboembolism can occur with mitral stenosis even if atrial fibrillation is not present.

What Are the Symptoms of Mitral Stenosis?

The most common symptoms caused by mitral stenosis are dyspnea (shortness of breath), cough, and fatigue. People with mitral stenosis are most likely to experience these symptoms any time the heart is called on to do a little more work, such as during exertion of any type, emotional stress, fever or other illness, or pregnancy.

Just as mitral stenosis itself develops very gradually, so do the symptoms it causes. In many cases, people with mitral stenosis avoid symptoms by subconsciously reducing their activity level over a period of years, eventually becoming quite sedentary. Because they are so inactive, they often will not actually notice the breathing issue, and may not report this symptom to their doctors.

When mitral stenosis becomes severe, patients may develop persistent symptoms even at rest, and may also develop severe edema and cough up blood.

Arial fibrillation can produce palpitations and lightheadedness, and can make all the symptoms associated with mitral stenosis much worse.

How Is Mitral Stenosis Diagnosed?

The diagnosis is often first suspected after the doctor performs a physical examination and notices the soft, rumbling heart murmur that is characteristic of mitral stenosis. Once the diagnosis is suspected, it can be easily confirmed or ruled out with an echocardiogram.

Treating Mitral Stenosis

If you have been diagnosed with mitral stenosis, the most important things you and your doctor will have to consider are whether/when to perform a surgical procedure to relieve the stenosis, and what steps need to be taken to prevent thrombosis.

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Article Sources
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