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Stenosis, Mitral Valve

Definition :
Mitral valve stenosis — or mitral stenosis — is a condition in which the heart's mitral valve is narrowed. This narrowing blocks the valve from opening properly and obstructs blood flow between the left chambers of your heart.

When the mitral valve is narrowed (stenotic), blood can't efficiently move through your heart and from your heart to the rest of your body. Mitral valve stenosis can leave you fatigued and short of breath, among other problems.

The main cause of mitral valve stenosis is a childhood infection called rheumatic fever, which is related to strep infections. Rheumatic fever — once common in the United States and still prevalent in developing countries — can scar the mitral valve.

Mitral valve stenosis in people of all ages is treatable. Treatment depends on the severity and progression of your condition and your signs and symptoms. If the condition is severe enough, you may need heart surgery to repair or replace the valve. Left unchecked, mitral valve stenosis can lead to serious heart complications.

Causes :
The heart, the center of your circulatory system, consists of four chambers. The two upper chambers, the atria, receive blood. The two lower chambers, the ventricles, pump blood.

Blood flows through your heart's chambers, aided by four heart valves. These valves open and close to let blood flow in only one direction through your heart :

  • Tricuspid valve
  • Pulmonary valve
  • Mitral valve
  • Aortic valve

The mitral valve — which lies between the two chambers on the left side of your heart — consists of two triangular-shaped flaps of tissue called leaflets. The leaflets of the mitral valve connect to the heart muscle through a ring called the annulus. Anchoring the mitral valve to the left ventricle are tendon-like cords, resembling the strings of a parachute, called chordae tendineae cordis.

Heart valves open like a trapdoor. The mitral valve is forced open when blood flows from the left atrium into the left ventricle. When all of the blood has gone through the valve, the leaflets swing closed to prevent the blood that has just passed into the left ventricle from flowing backward, in the wrong direction.

A defective heart valve is one that fails to either open or close fully. When a valve doesn't close tightly, blood can flow backward. This backward flow through a valve is called regurgitation (insufficiency). When a valve becomes narrowed and blood flow through it is limited, the condition is called stenosis.

Mitral valve stenosis is narrowing of the mitral valve. Many factors can tighten this passageway between the heart's left-sided chambers, obstructing blood flow into the heart's left ventricle. Causes of mitral valve stenosis include :

  • Rheumatic fever. A complication of strep throat infection, rheumatic fever can damage the mitral valve, leading to mitral valve stenosis later in life. Rheumatic fever is the most common cause of mitral valve stenosis. It can damage the mitral valve in two main ways. The infection may cause the leaflets of the valve to thicken, limiting the valve's ability to open. Or the infection may cause the leaflets of the mitral valve to fuse somewhat together, preventing the valve from opening and closing properly. People with rheumatic fever may have both mitral valve stenosis and regurgitation.
  • Congenital heart defect. Some babies are born with a narrowed mitral valve and develop mitral valve stenosis early in life. Babies born with this problem usually require heart surgery to correct the valve. Others are born with a malformed mitral valve that puts them at risk of developing mitral valve stenosis when they're older. In most cases, doctors don't know why a heart valve fails to develop properly in a newborn, infant or child, and it's not something that can be prevented. Congenital mitral valve stenosis is rare — and even rarer in isolation. It usually occurs as a component of other heart defects present at birth.
  • Other causes. Rarely, growths, blood clots or tumors can block the mitral valve, mimicking mitral valve stenosis. As you age, excessive calcium deposits can build up around the mitral valve, which sometimes causes significant mitral valve stenosis. Radiation treatment to the chest and some medications also may cause mitral valve stenosis.

Risk Factor :
Mitral valve stenosis is less common today than it was several decades ago because the most common cause, rheumatic fever, has largely been eradicated in the United States. However, rheumatic fever remains a frequent problem in countries where antibiotic use isn't as common.

Risk factors for mitral valve stenosis include a history of rheumatic fever and recurrent strep infections. Radiation treatment involving the chest can result in mitral valve stenosis. Other unusual causes of mitral valve stenosis include medications, such as ergot preparations used for migraine headaches.

Symptoms :
You can have mitral valve stenosis and feel well, or you may have only minimal signs and symptoms for decades. However, mild problems can suddenly get worse. See your doctor if you develop signs and symptoms of mitral valve stenosis, which can include :
  • Fatigue, especially during times of increased activity
  • Shortness of breath, especially with exertion or when you lie down
  • Swollen feet or ankles
  • Heart palpitations — sensations of a rapid, fluttering heartbeat
  • Frequent respiratory infections, such as bronchitis
  • Heavy coughing, sometimes with blood-tinged sputum
  • Rarely, chest discomfort or chest pain

Signs and symptoms of mitral valve stenosis — which may resemble those of other heart or heart valve conditions — may appear or worsen anytime you increase your heart rate, such as during exercise. An episode of rapid heartbeats also may accompany these signs and symptoms. Or they may also be triggered by pregnancy or other stress on your body, such as a respiratory infection or heart infection.

Signs and symptoms of mitral valve stenosis commonly include those of congestive heart failure — a complication of mitral valve stenosis and other heart problems. In mitral valve stenosis, pressure builds up in the heart and is transmitted back to the lungs resulting in fluid buildup (congestion) and shortness of breath.

Signs and symptoms of mitral valve stenosis often appear between the ages of 20 and 50, but they can occur at any age — even during infancy. Depending on the amount of narrowing, an infant or a child with mitral valve stenosis may have no symptoms, may tire easily or may have shortness of breath with vigorous physical activity.

Mitral valve stenosis may also produce a number of signs that only your doctor will be able to find. These may include :

  • Heart murmur
  • Lung congestion
  • Irregular heart rhythms (arrhythmias)
  • Pulmonary hypertension
  • Blood clots

Diagnosis :
If you develop signs or symptoms of mitral valve stenosis — for example, if you experience sudden breathlessness with mild exertion — your doctor may ask you to undergo several types of diagnostic tests.

But first your doctor will ask about your medical history and give you a physical examination. As part of your examination, he or she listens carefully to your heart through a stethoscope. Mitral valve stenosis causes an abnormal heart sound, called a heart murmur. Normal heart valves open silently to permit the flow of blood. A narrowed mitral valve can make a distinct snapping sound followed by a rumbling murmur.

In addition to listening to your heart, your doctor listens to your lungs and the sounds of your breathing. Your doctor is checking for lung congestion — the buildup of fluid in your lungs — that can occur with mitral valve stenosis.

From the initial information, your doctor decides which tests to request to make a diagnosis. For testing, you may be referred to a cardiologist — a doctor who specializes in the study of the heart and its function.

Diagnostic tests
Common tests to diagnose mitral valve stenosis include :

  • Echocardiogram. This test uses sound waves to produce an image of your heart. In an echocardiogram, sound waves are directed at your heart from a wand-like device (transducer) held on your chest. Sound waves bounce off your heart and are reflected back through the chest wall and processed electronically to provide video images of your heart in motion. An echocardiogram helps your doctor closely examine the mitral valve. The image shows the structure of the mitral valve and how it moves during the beating of your heart. Does it open wide to let blood flow through? Does it close fully? Is it misshapen? With an echocardiogram, your doctor can also measure the speed and direction of blood flow through your heart.
  • Electrocardiogram (ECG). In this test, patches with wires (electrodes) are attached to your skin to measure the electrical impulses given off by your heart. Impulses are recorded as waves displayed on a monitor or printed on paper. An ECG can give information about your heart rhythm and, indirectly, heart size. With mitral valve stenosis, some parts of your heart may be enlarged and you may have atrial fibrillation, a heart rhythm irregularity. Your doctor may ask you to walk on a treadmill or pedal a stationary bike while undergoing an ECG, to see how your heart responds to exertion.
  • Holter monitoring. A Holter monitor is a portable device that you wear to record a continuous ECG, usually for 24 to 72 hours. Holter monitoring is used to detect intermittent heart rhythm irregularities that may accompany mitral valve stenosis.
  • Chest X-ray. An X-ray image of your chest allows your doctor to check the size and shape of your heart to determine whether the left atrium is enlarged — a possible indicator of mitral valve stenosis. A chest X-ray also helps your doctor check the condition of your lungs. Mitral valve stenosis may lead to blood backing up in your lungs, which causes congestion that's visible on an X-ray.
  • Transesophageal echocardiogram. This type of echocardiogram allows an even closer look at the mitral valve. Your esophagus, the tube that runs from your throat to your stomach, lies close to your heart. In a traditional echocardiogram, a transducer is moved across your chest. In a transesophageal echocardiogram, a small transducer attached to the end of a tube is inserted down your esophagus. Because your esophagus lies close to your heart, having the transducer there provides a clear picture of the mitral valve and blood flow through it.
  • Cardiac catheterization. In this procedure, your doctor threads a thin tube (catheter) through a blood vessel in your arm or groin to an artery in your heart. A dye injected through the catheter fills your heart's arteries, and the arteries become visible on an X-ray. This test gives your doctor detailed information about the health of your heart. Some catheters used in cardiac catheterization have miniature devices (sensors) at the tips that can measure pressure within heart chambers, such as the left atrium.

Cardiac tests such as these help your doctor distinguish mitral valve stenosis from other heart conditions, including other problems of the mitral valve. Mitral regurgitation is a condition in which the mitral valve doesn't close tightly. Mitral valve prolapse is a disorder in which the mitral valve sags instead of closing tightly. These conditions may also require treatment.

If you receive a diagnosis of mitral valve stenosis, these tests also help reveal the cause, determine how serious the problem is, and determine whether the mitral valve can be repaired or if replacement may be necessary.

Complications :
Left unchecked, mitral valve stenosis can lead to complications such as :

  • Congestive heart failure. Congestive heart failure is a condition in which your heart is damaged and can't pump sufficient blood to meet your body's needs. A narrowed mitral valve interferes with blood flow through your heart and from your heart out to the rest of your body. In addition, pressure builds up in your lungs, leading to fluid accumulation. Eventually this places a strain on the right side of the heart, which leads to fluid buildup in either your ankles or abdomen or both areas.
  • Heart enlargement. The pressure buildup of mitral valve stenosis results in enlargement of your heart's upper left chamber (atrium). At first this change helps your heart pump more efficiently, but eventually, it proves damaging to your heart's overall health. Additionally, pressure can build up in your lungs and cause pulmonary congestion and hypertension.
  • Atrial fibrillation. In mitral valve stenosis, the stretching and enlargement of your heart's left atrium may lead to a heart rhythm irregularity called atrial fibrillation. In atrial fibrillation, the upper chambers of your heart beat chaotically and rapidly.
  • Blood clots. Left untreated, atrial fibrillation can put you at risk of blood clots forming in the upper left chamber of your heart, where blood pools in mitral valve stenosis. Blood clots from your heart may break loose and travel to other parts of your body, causing serious problems. For example, a blood clot that travels to your brain and blocks a blood vessel there could cause a stroke. A transesophageal echocardiogram can help determine whether blood clots have formed in a heart with a narrowed mitral valve.
  • Lung congestion. Another possible complication of mitral valve stenosis is pulmonary edema — a condition in which blood and fluid back up into your lungs. This causes congestion of the lungs, leading to shortness of breath and, sometimes, coughing up of blood-tinged sputum.
It may be difficult to understand why you need treatment if you have mitral valve stenosis but still feel well. If you have severe mitral valve stenosis but are in otherwise good health, you may need valve surgery or a balloon procedure to prevent permanent damage to your heart.

Invasive treatment isn't always needed right away. If tests reveal that you have mild to moderate mitral valve stenosis and you have no symptoms, there's generally no need for immediate valve treatment. Instead, your doctor will talk with you about scheduling checkups to carefully monitor the valve so that surgery or balloon treatment can be done at the appropriate time. Medications can help ease symptoms of mitral valve stenosis.

In general, intervention is necessary if and when narrowing becomes severe and symptoms develop. If at any point you notice symptoms associated with mitral valve stenosis, let your doctor know so that you can be evaluated. Some people never need anything done to the mitral valve because they never develop severe mitral valve stenosis.

No medications can correct a defect in the mitral valve. However, certain drugs can minimize symptoms by easing your heart's workload and regulating your heart's rhythm.

For example, your doctor may prescribe diuretics to reduce fluid accumulation in your lungs or elsewhere. Anticoagulants can help to prevent blood clots from forming in a heart with a damaged valve. Your doctor may also prescribe drugs to treat atrial fibrillation or other rhythm disturbances associated with mitral valve stenosis.

If you have mitral valve stenosis, your doctor may recommend that you take antibiotics before certain dental or medical procedures. These procedures may increase the likelihood of bacteria entering your bloodstream that can cause an infection in your heart (endocarditis). Endocarditis is an infection of the heart's inner lining — the endocardium. Typically, the infection involves one of the heart valves, especially if it's already damaged. If the mitral valve is narrowed, it's more prone to infection than is a healthy valve.

You may need valve repair or replacement to treat mitral valve stenosis. The types of procedures include :

  • Balloon valvuloplasty. This procedure — which doesn't involve open-heart surgery — uses a soft, thin tube (catheter) tipped with a balloon to open up the mitral valve passageway. A doctor guides the catheter through a blood vessel in your arm or groin to your heart and into your narrowed mitral valve. However, to reach the mitral valve on the left side of your heart, doctors actually guide the catheter through the right side of your heart first and then create a very small hole in the center wall of the heart (septum) that separates the right and left upper chambers of your heart. In some people, this small hole exists naturally. Through this tiny hole — a shortcut — doctors can more easily reach the mitral valve. Once in position at the mitral valve, a balloon at the tip of the catheter is inflated. The balloon pushes open the mitral valve and stretches the valve opening, improving blood flow. The balloon is then deflated and the catheter with balloon is guided back out of your body. Once the catheter is removed, the tiny hole in the heart wall will seal on its own. Balloon valvuloplasty can relieve mitral valve stenosis and its symptoms. But it may not be appropriate if the valve is both tight (stenotic) and leaky (regurgitant). It's also not performed if there's a blood clot in a chamber of your heart, because of the risk of dislodging it. Balloon valvuloplasty may improve the blood flow through the valve for a while. However, over time the narrowing may recur.
  • Mitral valve repair. Surgery to repair without replacing the mitral valve may be an option. For example, some infants are born with a mitral valve in which the leaflets of the valve are fused together. Or in adults, the valve leaflets become scarred and fused. By surgically separating or shaving back these leaflets — a procedure called valvotomy or commissurotomy — doctors can eliminate mitral valve stenosis and improve blood flow. Or valve repair at any age may involve removing obstructions on or near the mitral valve. This helps clear the valve passageway. The surgeon may also make adjustments to the cords that anchor the valve leaflets to your heart, to improve valve function. You may need the procedure repeated if you redevelop mitral valve stenosis.
  • Mitral valve replacement. Your surgeon removes the narrowed mitral valve and replaces it with a mechanical valve or a tissue valve from a pig, cow or human cadaver donor. Pigs and cows have heart tissue similar to that of humans. Mechanical valves, made from metal, are durable, but they carry the risk of blood clots forming on or near the valve. If you receive a mechanical mitral valve, you must take an anticoagulant medication, such as warfarin (Coumadin), for life to prevent blood clots. Tissue valves rarely raise your risk of blood clots, but they tend to wear out faster than mechanical valves do and may need to be replaced. Your doctor can discuss the risks and benefits of each type of heart valve with you.

Mitral valve surgery may involve open-heart surgery. For open-heart surgery, you're given a general anesthetic. Through an incision the length of your breastbone (sternum), your heart is exposed and connected to a heart-lung machine that assumes your breathing and blood circulation function during the procedure. Your surgeon then replaces the narrowed mitral valve.

Less invasive techniques
Surgeons are working on developing less invasive techniques to treat valve disorders, such as repairing mitral valves using endoscopy, which uses smaller incisions, and using robotic surgical techniques.

Mitral valve stenosis can be completely eliminated with surgery. However, you may continue to be at risk of arrhythmias even after you've been treated for mitral valve stenosis. You may need to take medications to lower that risk.

Prevention :
The most effective way to prevent mitral valve stenosis is to prevent its most common cause, rheumatic fever. You can do this by making sure you and your children see your doctor when you have a sore throat. Untreated strep throat can develop into rheumatic fever. Fortunately, strep throat is easily treated with antibiotics.

You can help prevent the complication endocarditis, an infection of the mitral valve and inner heart, by taking antibiotics before certain dental and medical procedures. Ask your doctor if and when you should take antibiotics to prevent endocarditis.

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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