Mitral Regurgitation

Understanding the heart

The heart has four chambers - two atria and two ventricles. The walls of these chambers are mainly made of special heart muscle. During each heartbeat both of the atria contract first to pump blood into the ventricles. Then both ventricles contract to pump blood out of the heart into the arteries. There are one-way valves between the atria and ventricles, and between the ventricles and the large arteries coming from the heart. The valves make sure that when the atria or ventricles contract, the blood flows in the correct direction.

What is the mitral valve?

The mitral valve lies between the left atrium and left ventricle. It allows blood to flow into the left ventricle when the left atrium contracts. However, when the left ventricle contracts, the mitral valve closes and the blood flows out through the aortic valve into the aorta (the main artery which takes blood to the body).

The mitral valve has two flaps or 'cusps'. The cusps are prevented from turning 'inside out' by thin strands of tissue called chordae. The chordae (not shown in the diagram) anchor the cusps to the inside wall of the ventricle. The valve or chordae may become damaged or scarred which can prevent the valve from working properly. This can lead to disorders called mitral stenosis, mitral regurgitation, or a combination of these two.

What is mitral regurgitation?

Mitral regurgitation is sometimes called mitral insufficiency or mitral incompetence. In mitral regurgitation the valve does not close properly. This causes blood to leak back (regurgitate) into the left atrium when the left ventricle contracts. Basically, the more 'open' the valve remains, the more blood 'regurgitates', the more severe the problem.

What are the causes of mitral regurgitation?

Mitral regurgitation can occur if the valve is weakened or damaged. Causes include:

Rheumatic heart disease

Rheumatic heart disease is a general term which means any heart problem which develops after having an episode of rheumatic fever.

Rheumatic fever is a condition which sometimes follows an infection with a bacterium (germ) called the streptococcus. You body makes antibodies to the bacterium to clear the infection. But in some people the antibodies also 'attack' various parts of the body, in particular the mitral valve. Inflammation of the valve develops which can cause permanent damage and lead to thickening and scarring years later.

Rheumatic fever used to be common in the UK in the era before antibiotics, but is now rare. It is still quite common in some developing countries.

Mitral valve prolapse

This is also called 'floppy' mitral valve. In this condition the valve is slightly deformed and 'bulges' back into the let atrium when the ventricle contracts. This can let a small amount of blood leak back into the left atrium. As many as 1 in 20 people have some degree of mitral valve prolapse. It most commonly occurs in young women. It usually causes no symptoms as the amount of blood that leaks back is often slight.

The cause of most cases of 'floppy valve' is unknown. It sometimes occurs with 'connective tissue' disorders such as Marfan's syndrome.

Other causes

Other causes are less common and include:

• Hypertrophic cardiomyopathy - a disease where the heart muscle thickens and can distort the mitral valve.
• A heart attack (myocardial infarction) can sometimes cause damage to the ventricle where the chordae are attached. This can cause rupture of the chordae which distorts the mitral valve.
• Congenital heart problems. It is then usually part of a complex heart deformity.
• Infection of the valve (endocarditis).
• A complication of various other diseases.

What effects does mitral regurgitation have?

As the valve does not close properly, some blood is pumped back into the left atrium when the left ventricle contracts. Minor leaks do not matter much. However, with larger leaks, it causes an increase in the pressure in the atrium. Therefore, the wall of the atrium may become thicker (hypertrophy) and the atrium may enlarge (dilate). A 'back pressure' of blood may then cause congestion of blood in the blood vessels which bring blood to the left atrium (the pulmonary veins which bring blood from the lungs).

Also, if a lot of blood leaks into the left atrium when the left ventricle contracts, less blood is pumped into the body via the aorta. The heart compensates for this. The wall of the left ventricle may become thicker, the ventricle may enlarge, and the heart rate may increase.

What are the symptoms of mitral regurgitation?

The severity of symptoms can vary greatly depending on the underlying cause, how much blood leaks, and whether or not the left ventricle is diseased. Some people with mild regurgitation have no symptoms. If symptoms occur they can include:

• Shortness of breath. This tends to occur on exercise at first, but occurs at rest if the regurgitation becomes worse. This symptom is due to the congestion of blood and fluid in the blood vessels in the lungs.
• Fainting, dizziness or tiredness.
• Chest pains (angina) may develop if there is a reduced blood flow to the coronary arteries or if not enough blood gets to the thickened ventricle.
• The pulse may be faster than normal.

The symptoms often develop gradually over years. However, they can develop quickly if the damage to the valve occurs quickly (for example, following a heart attack).

What complications may occur with mitral regurgitation?

• Atrial fibrillation may develop in more severe cases. This is where the heart beats in a fast and irregular way. This occurs because the electrical signals in an enlarged atrium become faulty. The irregular heat rhythm can cause palpitations, and make you even more breathless. (See separate leaflet called 'Atrial Fibrillation'.)
• Heart failure may develop and gradually become more severe. This causes worsening shortness of breath, tiredness, and fluid retention in various tissues of the body. (See separate leaflet called 'Heart Failure'.)
• A blood clot may form within an enlarged left atrium. This is more likely if you have atrial fibrillation. A blood clot may travel through the heart, be carried in the bloodstream and get stuck and block a blood vessel in another part of the body. For example, it may get stuck in a blood vessel going to the brain and cause a stroke.
• Endocarditis sometimes develops. This is an infection of the valve. (Damaged valves are more prone to infection than normal valves.) Unless promptly treated, endocarditis can cause serious illness. (See leaflet called 'Infective Endocarditis'.)

How is mitral regurgitation diagnosed?

A doctor may hear a heart murmur or other abnormal noises when listening with a stethoscope. Murmurs and noises are due to blood passing through abnormal valves, or to abnormal movement of valves. There are typical murmurs and noises that occur with mitral regurgitation. An ultrasound scan of the heart called an echocardiogram (heart echo) can confirm the diagnosis.

What are the treatments for mitral regurgitation?

Medication

Mild cases may not require any regular medication. If you develop symptoms or complications, various medicines may be advised. For example:

• Diuretics (water tablets) usually help if you are breathless. They make the kidneys produce more urine. This gets rid of excess blood and fluid which may build up in the lungs or other parts of the body with the 'back pressure' from the heart.
• ACE Inhibitors are medicines which help to reduce the amount of work the heart does and ease symptoms of heart failure.
• Anti-arrhythmic medication may be needed to control your heart rate if you develop atrial fibrillation.
• Warfarin ('anticoagulation') is usually advised if you develop atrial fibrillation. This helps to prevent blood clots from forming.

Surgical treatments

Surgical treatment is needed in more severe cases.

• Valve repair may be an option in some cases.
• Valve replacement is needed in some cases. This may be with a mechanical or a tissue valve. Mechanical valves are made of materials which are not likely to 'react' with your body, such as titanium. Tissue valves are made from treated animal tissue, such as valves from a pig.

If you need surgery, a surgeon will advise on which is the best option for your situation.

Antibiotics to prevent endocarditis

You will normally be advised to take a short course of antibiotics if you have certain surgical procedures such as cystoscopy or colonoscopy. During these procedures, some bacteria may be 'pushed' into the bloodstream. The 'antibiotic cover' aims to kill any bacteria which may get into the bloodstream and helps to prevent endocarditis (described above). Most doctors who do these surgical procedures are aware of the need to recommend antibiotic cover to people with heart valve disease. The British Heart Foundation (contact details below) also lists a range of procedures that require antibiotic cover.

Dental treatments: until recently, it has also been advised that people with heart valve disease should take antibiotic cover when they have dental treatment. However, a guideline published in 2006 from the British Society for Antimicrobial Chemotherapy (BSAC) says that this is not needed in most situations. Their information aimed at patients says:

"A BSAC group of experts has spent a lot of time carefully looking at whether dental treatment procedures are a possible cause of infective endocarditis (IE) [sometimes called bacterial endocarditis (BE)], which is infection of the heart valve. After a very detailed analysis of all the available evidence they have concluded that there is no evidence that dental treatment procedures increase the risk of these infections.

Therefore it is recommended that the current practice of giving patients antibiotics before dental treatment be stopped for all patients with cardiac abnormalities, except for those who have a history of healed IE, prosthetic heart valves and surgically constructed conduits.

The main reasons for this are the lack of any supporting evidence that dental treatment leads to IE and the increasing worry that administration of antibiotics may lead to other serious complications such as anaphylaxis (severe allergy) or antibiotic resistance.

The advice from the BSAC is that patients should concentrate on achieving and keeping a high standard of oral and dental health, as this does reduce the risk of endocarditis. Help for this will be provided by your Dental Professional."

However, this guideline is controversial. It has caused a lot of debate, especially from some cardiologists (heart doctors) and dentists who maintain that antibiotic cover is still needed for dental procedures. See references below for details of some articles that deal with this controversy. Your own doctor or dentist will advise for your own particular circumstance.

What is the prognosis (outlook) for people with mitral regurgitation?

In some cases the disorder is mild and causes no symptoms. If you develop symptoms they tend to become gradually worse over the years. However, the speed of decline can vary. In many cases it can take years for symptoms to become serious. Medication can ease symptoms, but cannot reverse a damaged valve.

Surgical treatment has greatly improved the outlook in most people with more severe regurgitation. Surgery has a very good success rate.

Further help and information

British Heart Foundation

14 Fitzhardinge Street, London, W1H 6DH
Tel - Heart Information Line: 08450 70 80 70
Web: www.bhf.org.uk