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Mitral Valve Stenosis (MVS)

 

INTRODUCTION

Valves are the trusty cross-guards of the pump that is our heart. They ensure and direct the correct flow of blood between its various chambers. However, due to a multitude of causes, these valves can become defective, limiting their ability to perform this critical function.

 

The mitral valve sits in between the left atrium and the left ventricle. It allows blood to flow from the left atrium to the left ventricle and prevents it from leaking backward.

 

Mitral valve stenosis is the hardening, stiffness or scarring of the mitral valve. This is generally tolerated poorly as it worsens. The pressure in the left atrium has to remain low for the lungs to work properly. The left atrium receives flow from the veins that drain the lung. Any problem with the mitral valve will result in a pressure build-up in the left atrium, which will cause blood to back up in the lung. This causes people to feel short of breath.

 

This condition in adults is generally observed as a complication of rheumatic fever. Often times, a balloon can be used to open the valve. Another form of mitral stenosis is caused in older people as the ring around their valve hardens with calcium (this is what makes bone hard). We call this MAC (mitral annular calcification) and it cannot be treated with a balloon. There are also congenital (patients are born with it) causes.

What does this mean for me?

As the heart pumps, the mitral valve opens to allow blood to flow from the left atria into the left ventricle. The flaps of the valve are shut in between heartbeats, ensuring that there is no backflow of blood once it is pumped into the ventricle.

 

When the valve becomes stenotic (narrowed) and/or regurgitant (leaky), this function is impaired.  If the valve becomes stenotic (narrowed) blood is impaired from exiting the left atrium. If the valve becomes regurgitant (incompetent), blood is able to reflux back into the left atrium after it has already entered the left ventricle.

 

The opening of the normal mitral valve is 4-6 cm² and gradually decreases to 2-2.5cm², at which point certain stressors can cause symptoms. Severe stenosis is characterized by an area of 1cm². Usually, if the valve area is less than 1.5cm²  in the presence of symptoms, we consider offering a balloon valvuloplasty.

 

As a result of a narrowed valve, patients can develop enlargement of the left atrium which in turn leads to atrial fibrillation. Atrial fibrillation is an irregular heart rhythm associated with fast heart rates and stroke, if patients remain untreated.

 
 

Symptoms: How would I know if I have MVS?

Although several signs and symptoms exist, it is important to note that they are more likely to occur  later in the course of mitral valve stenosis, and will vary depending on severity. The following are common signs of rheumatic mitral valve disease. It is important to note that these signs may occur in heart disease caused by various other causes.

 

  • Shortness of breath at rest or during exertion

  • Fatigue

  • Swelling in in the lower limbs

  • Feeling of irregular heart rhythm

  • Loss of consciousness or  fainting

 

The symptoms described above can worsen under certain conditions as well. These include exercise, pregnancy, or other body stresses such as infection.

 

In addition to these symptoms, a medical practitioner may also look for certain signs during his/her examination:

  • Heart murmur

  • High venous pressures

  • Fluid buildup in the lungs

  • Irregular heart rhythms (arrhythmias)

Causes: Why do I have MVS?

The causes of mitral valve stenosis, although explored widely, are still relatively unclear. It has been demonstrated, however, that women exhibit greater risk than men. Rheumatic mitral stenosis involves the bodies’ own immune system attacking their mitral valve over years, usually as a result of a previous heart infection.

 

The most common cause of mitral valve stenosis is rheumatic fever, which often results from untreated strep infections in children. Acute rheumatic fever usually affects the joints and heart by causing inflammation. In the heart, this inflammation can ultimately lead to scarring of the mitral valve, aortic valve and tricuspid valve resulting in narrowing of the valve opening or leaking. An episode of rheumatic fever affecting the heart is referred to as rheumatic carditis. This process is gradual; it can take 5 to 10 years for symptoms to be exhibited following an episode of rheumatic fever.

 

Other causes include non-rheumatic calcification of the structures surrounding the valve, including the leaflets/flaps of the valve which can cause increased rigidity and limit valve function. Furthermore, congenital defects, chest exposure to radiation, rheumatoid arthritis and the autoimmune disease, lupus, among others are also less common causes of mitral valve stenosis.

Next Steps: Investigation Plan

Through a review of your detailed medical history and subsequent physical examination, your physician can assess for mitral valve stenosis and treatment options. These include the presence of a heart murmur or abnormal sound and lung congestion. Your doctor will refer you to a cardiologist for further diagnostic tests in such a scenario.

 

Your cardiologist may use a number of tools and techniques to follow up on the potential presence of mitral valve stenosis and to make an accurate diagnosis. These include:

 

1) Transthoracic echocardiogram: This is a heart ultrasound. The transducer emits sound waves directed at your heart to produce images that will show the presence of abnormalities.

 

2) Electrocardiogram (ECG): Electrodes are placed on the patient’s chest, and the electrical activity of the heart is measured to indicate any abnormalities in their heart rhythm

 

3) Chest X-ray

 

4) Transesophageal echocardiogram: The transesophageal echocardiogram is a test where a special ultrasound probe is swallowed. This allows detailed evaluation of the mitral valve and left atrium. It is especially helpful in mitral stenosis to exclude clot.

 

5) Cardiac catheterization: A cardiac catheterization allows pressure measurement inside the heart and allows for determination of the arteries around the heart. The pressures in the lung can also be assessed and it can allow for valve assessment.

 

The purpose of these diagnostic tools is to accurately pinpoint the source of the symptoms you are experiencing, which is extremely important before we decide on therapy. These techniques will help your cardiologist to determine which valve is affected and if there are any additional problems which could affect management.  After a detailed evaluation we can decide whether this valve can be replaced or repaired, and any other information that could help to inform your decision about treatment options.

Treatment Options for MVS

Treatment depends on a variety of factors, including the state of the heart and lungs, symptoms and patient characteristics such as age and comorbidities.

 

For patients who are experiencing little or no symptoms, only medical treatment may  be needed.

 

Patients who are experiencing symptoms may be prescribed a number of drugs. These may include beta blockers to reduce the heart rate, diuretics to reduce edema and improve breathing, angiotensin converting enzyme inhibitors to reduce blood pressure, and digoxin to reduce heart rate in patients with heart failure or arrhythmias. In addition to this, blood thinners may be used to prevent blood clots in patients with heart rhythm irregularities in conjunction with the aforementioned drugs. The exact treatment regimen prescribed by your cardiologist will be patient-specific.

 

Balloon mitral valvuloplasty is an excellent treatment for patients with mitral stenosis and symptoms of shortness of breath. Balloon valvuloplasty can result in the mitral valve opening more thus allowing blood to more easily drain from the lungs.

 

Your doctor will carefully review specific features of your echocardiagram to decide whether you are a candidate.  Important items include:

  1. Your valve area

  2. Degree of leaking

  3. Degree of leaflet thickening

  4. Degree of calcification (hardening) of the valve and surrounding structures

  5. Degree of involvement of the subvalvular structures

  6. The presence of clot in the heart

 

If you are a candidate for mitral valvuloplasty your doctor will discuss any specific procedural risks or potential problems.

 

For some people their valves are too rigid and calcified to consider balloon valvuloplasty and surgery must be considered. Mitral valve replacement is a well established operation carried out by heart surgeons. Under general anesthesia, and on a heart lung machine, the heart is stopped and opened and a new valve is sewn into place.

Long Term Health Implications

 
 
 

The effect on the heart due to mitral valve stenosis is primarily related to the increased stretch on the left atria and the pressure backup that results in making it difficult for blood to empty out of the lung circulation. If the mitral valve also leaks as well as being narrow, the pressure buildup is worsened. When blood cannot empty out of the lungs after taking on oxygen, the higher pressure in the lungs results in shortness of breath and the inability to get blood to the body results in fatigue and exhaustion.

 

The increased left atrial size places patients at risk of irregularities in their heart rhythm, and blood clot formation due to stagnant blood in the heart. These blood clots can become dislodged and travel to vital organs, including the brain which may result in a stroke.

 

Due to the increased pressure in the lungs, fluid can seep out of the lung arteries and veins making the lungs heavy and stiff. This results in shortness of breath and what we call “heart failure”, which is the inability of the heart to pump adequately enough to empty the lungs. Eventually, this will be observed in most untreated mitral valve stenosis.

 

This further validates the importance of seeing your cardiologist, should any of the aforementioned symptoms arise.

Frequently Asked Questions

 

Are there any lifestyle restrictions following procedure?


In general, there are no lifestyle restrictions but activities should be limited by symptoms and common sense.

 

 

Will I need any further treatments following treatment?


You will have a follow-up visit with your doctor several months post procedure to check on your progress. An echocardiogram will be done to reassess your valve. Your doctor will also review your medication with you.

 

 

Can I play sports?

 

Fitness is encouraged but it is recommended that you avoid contact sports.

 

Will OHIP (public insurance) cover my procedure?

 

Yes. All mitral valve procedures are covered by OHIP.

 

 

How urgent is the treatment?

 

Once you are symptomatic, it is advisable to receive medical treatment as soon as it is feasible. Even if you have seen your doctor and a procedure is planned, it is a good idea to advise their office if there is a change in symptoms.  For any serious acute or concerning symptoms, please go immediately to the closest emergency room.

Questions?

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Toronto General Hospital 

 200 Elizabeth Street | 6E - 249

Toronto, Ontario M5G 2C4

Tel: 416-340-3835

Fax: 416-340-3000

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