Mitral Stenosis

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What is mitral stenosis?

Mitral stenosis is a condition where the mitral valve is narrowed. The valve does not open fully, which means only a limited amount of blood is able to flow through it.

Mitral stenosis

Mitral Stenosis. The image on the left is the normal mitral valve which looks like a ‘fish mouth’. In mitral stenosis, the valve leaflets are thicker, and the opening is restricted.

How common is mitral stenosis?

While mitral stenosis is not very common in the western world, it appears to be fairly common in India.

What causes mitral stenosis?

The most common cause of mitral stenosis in India is a condition called rheumatic fever. However, there are other causes as well that include the following –

  • Congenital mitral stenosis – This is a birth defect and babies are born with narrowed mitral valves
  • Systemic Lupus Erythematosus (SLE) – This is an ‘autoimmune’ condition where the body fights its own cells. It can affect the heart and other organs as well.
  • Rheumatoid arthritis – This is a condition where the patient suffers from joint pains. Rare cases may have mitral stenosis

These causes are rare, and the most common cause in India remains suffering from rheumatic fever as a child. However, it must be noted that it takes many years before mitral stenosis develops and starts to cause any symptoms. In other words, if a child has rheumatic fever, it can be a number of years before mitral stenosis actually develops.

That being said, having rheumatic fever as a child does not mean that mitral stenosis will develop in childhood.

What happens in mitral stenosis?

In mitral stenosis, the area of the mitral valve opening is markedly reduced. Normally, when the mitral valve opens, there is an orifice that is generated that allows blood to flow from the left atrium to the left ventricle. This area ranges between 4 to 6 cm².

In mitral stenosis, this area starts to reduce gradually.  In the initial stages it can be mild but as time progresses it could become severe. Patients begin to experience symptoms in the valve area ranges between 2 and 2.5 cm².

But what exactly happens when mitral stenosis develops? In simple terms, if one were to imagine the left side of the heart to consist of two chambers that are placed one on top of the other and separated by the mitral valve, it would make sense that the blood will flow from the top chamber to the bottom chamber when the mitral valve opens. However, if the mitral valve does not open completely, the quantity of blood in the top chamber can increase leading to it becoming bigger and bigger in size.

The top chamber of the heart is directly connected to the lungs. If the pressure in the top chamber i.e. left atrium  increases, this increase in pressure is reflected in the lungs as well. This can cause leakage of fluid into the lungs resulting in difficulty breathing especially on exertion. This condition where the pressure in the lungs is increased is called pulmonary hypertension.

Over time,  as the pressure in the lungs increases, the right side of the heart (which is also connected to the lungs) begins to become bigger and weaker. This can cause further problems.

A combination of all these problems can lead to weakening of the heart muscle.  This can cause a number of different symptoms which can make the patient very unwell.

What are the symptoms of mitral stenosis?

In patients with mild mitral stenosis, there may not be any symptoms at all. Sometimes mitral stenosis is picked up on a routine clinical examination or on echocardiography.

The symptoms of mitral stenosis may begin to present themselves after the age of 30 to 40 years. The presence of a concurrent illness such as an overactive thyroid,  anaemia (low haemoglobin), atrial fibrillation and other conditions such as pregnancy and exercise can sometimes precipitate the symptom of breathing difficulty.

Some patients who have mitral stenosis can develop palpitations which are experienced as a ‘fast and irregular thumping’ in the chest. These palpitations are due to atrial fibrillation. The presence of atrial fibrillation  can increase the chance of the patient developing a stroke.

Some patients who have advanced mitral stenosis may notice a change in the character of the voice.  This hoarseness of the voice is brought about by the enlarged left atrium (discussed above)  compressing a nerve called the recurrent laryngeal nerve. The recurrent laryngeal nerve is responsible for maintaining the function of the vocal cords and any damage to this nerve can ead to a change in the character of an individual’s voice.

A small number of patients may develop a cough and may be bring up blood  in the process. This is a rare and is not life-threatening.

In a nutshell, the symptoms of mitral stenosis of the following –

  • No symptoms in mild mitral stenosis. This can last for years.
  • Breathing difficulty which is worse when lying down and on exertion
  • Tiredness (fatigue) during physical activity
  • Hoarseness of voice
  • Palpitations (irregular thumping in the chest) due to atrial fibrillation
  • Swelling of the legs
  • Chest discomfort
  • Headaches
  • Complications
    • Stroke
    • Atrial fibrillation
    • Fluid in the lungs (pulmonary edema)
    • Infective endocarditis – This refers to infection of the mitral valve
    • Pulmonary hypertension – This is increased blood pressure in the lungs
    • Heart failure i.e. weakening of the heart muscle

Mitral stenosis can be a problem during pregnancy. This topic has been discussed  here.

On examination of a patient with mitral stenosis, the doctor may hear a heart murmur and the presence of fluid on the lungs. The pulse and the heart rate may be irregular.

Diagnosis of mitral stenosis

A diagnosis of mitral stenosis can be made from a detailed clinical history and examination by the cardiologist. The presence of associated complications can also be detected through clinical examination.

In order to confirm the diagnosis, certain tests may need to be performed. These tests include the following.

1. Transthoracic echocardiogram

This is the best test to diagnose  mitral stenosis.  The valve area will be visibly reduced and a good estimation of the valve area can be made. Problems such as an enlarged left atrium and leaking of the mitral valve can also be seen. To read more on echocardiography, click here.

2. Chest x-ray

A chest x-ray is useful in determining if there is fluid present on the lungs. In addition, the heart size can also be determined.

3. Electrocardiogram (ECG)

An ECG can help determine any changes in the electrical activity of the heart. a change in the size of the heart or of any individual chambers may be detected through this test.

4. Trans-esophageal echocardiography

A trans-esophageal echocardiogram is a specialised test that involves the passage of a thin tube through the food pipe all the way down to the middle of the chest. At the end of the tube is present an ultrasound device that can transmit images of the heart onto a computer screen.

This test is an excellent test to determine the exact nature and degree of mitral stenosis. It is useful if patients have severe mitral stenosis and require some form of surgical treatment.

5. Coronary angiography

This test is not essential in making a diagnosis of mitral stenosis but may be performed if patients require surgery to treat mitral stenosis. It is done to determine if a patient has problems with their heart arteries so that these may also be dealt with  during surgery.

Treatment of mitral stenosis

Patients who have mild or moderate mitral stenosis without any symptoms do not require any treatment. However, once symptoms develop, patients will require either medical or surgical therapy depending upon the severity.

Lifestyle changes

As far as lifestyle changes go,  there are no specific measures that can prevent mitral stenosis. However, performing  regular exercise, avoiding smoking and alcohol, eating healthily and getting a regular medical checkups are all part and parcel of maintaining good heart health. These must be observed at all times.

Medical therapy

There are no specific medicines that can help reverse mitral stenosis or completely cure it. The treatments that are prescribed only help manage the symptoms of any complications that may develop.

  • Diuretics (tablets that help get rid of water from the body) are useful in treating patients who have fluid in the lungs. Examples include Frusemide (Lasix), Aldactone,, Lasilactone  etc.
  • Beta-blocker drugs (Bisoprolol, Metoprolol, Carvedilol) can help slow down the heart rate and promote effective contraction of the heart.
  • Calcium channel blocker drugs (Diltiazem) can also slow down the heart rate, reduce the amount of work that the heart muscle to contract and increase the amount of blood that fills the heart muscle.
  • Blood thinning medication such as Acetrom or Warfarin can help keep the blood thin and prevent the formation of clots within the left atrium. These drugs are essential in preventing the development of a stroke.
  • Anti-arrhythmic drugs (digoxin, amiodarone) are useful in treating patients who have developed atrial fibrillation or any other type of irregular heartbeat.

As is evident, the drug is above can only help treat any symptoms or complications that the patient develops from mitral stenosis. However, it does not reverse the condition and neither does it cure it.

Surgical therapy is a way of opening up the mitral valve and allowing for better blood flow.  Some patients may undergo complete mitral valve replacement surgery.

Surgical therapy

There are a number of different procedures that are currently available. The less invasive procedure is called a balloon valvuloplasty. Open heart surgery such as a mitral valve commissurotomy and mitral valve replacement may be considered.

Balloon valvuloplasty

In this procedure, a small catheter that has a balloon at its tip is advanced by the doctor through a large blood vessel in the arm or groin all the way up to the heart. Once the balloon is present within the opening of the mitral valve, it is inflated. This inflating balloon pushes away the narrowed leaflets, thus creating a larger opening in between the valve leaflets. The balloon is then deflated and the catheter is removed.

Prior to performing balloon valvuloplasty, patients will need to undergo a detailed assessment to see whether or not they will benefit from the procedure. Balloon valvuloplasty can help relieve symptoms to an extent but it is not a permanent solution. Many patients may require repeat procedures in the future. This will be assessed by the cardiologist on a case-by-case basis.

Mitral valve commissurotomy

This is a surgical option that may be pursued if balloon valvuloplasty fails. It is an open heart surgery that requires the patient to go on a heart-lung bypass machine during the operation. The surgery aims at removing any thickened tissues or calcium deposited on the mitral valve. Doing so allows for better movement of the mitral valve and creates a larger opening  that allows good blood flow from the left atrium to the left ventricle.

Mitral valve replacement

This is another surgical procedure that involves the removal of the entire diseased mitral valve and replacement  with either a metallic valve or a tissue valve.metallic valves, also called mechanical valves require the patients to go on blood thinning medication to prevent the formation of blood clots on the valve. Tissue valves are derived either from a human cadavers, pig  or cow. The choice of valve can vary from patient to patient and depends on a number of different factors that will be taken into consideration by the surgeon. In addition,  the religious beliefs of the patient may also be taken into account especially when  considering a tissue valve replacement.

Is there a way to prevent mitral valve stenosis?

The best way to prevent the development of mitral stenosis in adult hood is to treat any sore throats that occur in childhood promptly with antibiotics. The responsibility does live with the parents to ensure that their children see a doctor if they develop a sore throat. A short course of antibiotics is often sufficient.


References

1.Carabello, Blase A. “Modern management of mitral stenosis.” Circulation 112.3 (2005): 432-437.

2. Mitral Stenosis – Medscape. http://emedicine.medscape.com/article/155724-overview

Read More

Mitral stenosis in pregnancy

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