What causes mitral stenosis?
Mitral stenosis is often caused by having had rheumatic fever. Rheumatic fever can cause an infection in the mitral valve. It can also cause an infection (in-FECK-shun) called endocarditis in the endocardium. The endocardium is the inner lining of the heart muscle. An infection in either the mitral valve or the endocardium can damage the leaflets in the mitral valve. Another cause of mitral valve damage is age. As some people get older, calcium or other material can build up on the
leaflets of the mitral valve. This build up can cause the leaflets to work poorly. Mitral stenosis can also be caused by a problem with your heart when you were born (birth defect). Rheumatic fever, age, and birth defects are the most common causes of MS. There are also less common causes.
The normal area of the mitral valve orifice is about 4 to 6 cm2. Under normal conditions, a normal mitral valve will not impede the flow of blood from the left atrium to the left ventricle during (ventricular) diastole, and the pressures in the left atrium and the left ventricle during diastole will be equal. The result is that the left ventricle gets filled with blood during early diastole, with only a small portion of extra blood contributed by contraction of the left atrium (the "atrial kick") during late ventricular diastole. When the mitral valve area goes below 2 cm2, the valve causes an impedement to flow of blood into the left ventricle, creating a pressure gradient across the mitral valve. This gradient may be increased by increases in the heart rate or cardiac output. As the gradient across the mitral valve increases, the amount of time necessary to fill the left ventricle with blood increases. Eventually, the left ventricle requires the atrial kick to fill with blood. As the heart rate increases, the amount of time that the ventricle is in diastole and can fill up with blood (called the diastolic filling period) decreases. When the heart rate goes above a certain point, the diastolic filling period is insufficient to fill the ventricle with blood and pressure builds up in the left atrium, leading to pulmonary congestion.
Since the normal left ventricular diastolic pressures is about 5 mmHg, a pressure gradient across the mitral valve of 20 mmHg due to severe mitral stenosis will cause a left atrial pressure of about 25 mmHg. This left atrial pressure is transmitted to the pulmonary vasculature. Pulmonary capillary pressures in this level cause an imballance between the hydrostatic pressure and the oncotic pressure, leading to extravasation of fluid from the vascular tree and pooling of fluid in the lungs (pulmonary congestion).
Increases in the heart rate will allow less time for the left ventricle to fill, also causing an increase in left atrial pressure and pulmonary congestion. When the mitral valve area goes less than 1 cm2, there will be an increase in the left atrial pressures (required to push blood through the stenotic valve). This increase in left atrial pressures will impede venous return to the left atrium from the lungs, causing pulmonary congestion (congestive heart failure).
The constant pressure overload of the left atrium will cause the left atrium to increase in size. As the left atrium increases in size, it becomes more prone to develop atrial fibrillation. When atrial fibrillation develops, the atrial kick is lost (since it is due to the normal atrial contraction). In individuals with severe mitral stenosis, the left ventricular filling is dependant on the atrial kick. The loss of the atrial kick due to atrial fibrillation can cause a precipitous decrease in cardiac output and sudden congestive heart failure. |
More information on mitral valve diseases (mitral valve prolapse, mitral valve regurgitation, mitral stenosis)
What is mitral valve disease? - There are many diseases which affect the mitral valve and its supporting structures. The most common disorder of the mitral valve is the partial backflow.
What is mitral valve prolapse? - Mitral valve prolapse (MVP) is a heart valve condition marked by the displacement of a thickened mitral valve leaflet into the left atrium during systole.
What causes mitral valve prolapse? - The cause of mitral valve prolapse is unknown. It is more common in people with low body weight and low blood pressure.
What're the symptoms of mitral valve prolapse? - Symptoms of mitral valve prolapse include fatigue, palpitations, chest pain, anxiety, migraine headaches, and even stroke.
How is mitral valve prolapse diagnosed? - Mitral valve prolapse is diagnosed in the course of a physical examination. Echocardiography is useful in diagnosing a prolapsed mitral valve.
What're the treatments for mitral valve prolapse? - Most people with mitral valve prolapse (MVP) do not have symptoms or need treatment. Mitral valve prolapse can be treated with surgical replacement of the mitral valve.
What is mitral valve regurgitation? - Mitral valve regurgitation happens when some of the blood in your heart leaks from the left ventricle into the left atrium.
What causes mitral valve regurgitation? - The causes of primary mitral regurgitation include myxomatous degeneration of the mitral valve, ischemic heart disease, coronary artery disease.
What're the symptoms of mitral regurgitation? - The symptoms associated with mitral regurgitation are dependent on which phase of the disease process the individual is in.
What're the complications of mitral regurgitation? - Complications of mitral regurgitation include congestive heart failure, atrial fibrillation, blood clot, endocarditis.
How is mitral regurgitation diagnosed? - The diagnosis of mitral regurgitation usually employs imaging studies such as echocardiography or magnetic resonance angiography of the heart.
What're the treatments for mitral regurgitation? - The treatment of mitral regurgitation depends on the acuteness of the disease and whether there are associated signs of hemodynamic compromise.
What is mitral valve stenosis? - Mitral valve stenosis is a narrowing of the opening of the mitral valve in the heart. Stenosis of the mitral valve prevents the valve from opening normally.
What causes mitral stenosis? - Mitral stenosis is often caused by having had rheumatic fever. Rheumatic fever can cause an infection in the mitral valve.
What are the symptoms of mitral stenosis? - Symptoms of mitral stenosis include shortness of breath, fainting, dizziness or tiredness, chest pains (angina), chest infections.
How is mitral valve stenosis diagnosed? - Mitral valve stenosis is usually detected by a physician listening to heart sounds. The diagnosis of mitral stenosis is most easily made by echocardiography.
What're the treatments for mitral stenosis? - The treatment options for mitral stenosis include medical management, surgical replacement of the valve, and percutaneous balloon valvuloplasty.
Mitral valve repair and replacement - Mitral valve replacement surgery is open-heart surgery that is done while the patient is under general anesthesia. |
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