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 squeezes (contracts). However, when the left ventricle contracts, the mitral valve closes and the blood flows out through the aortic valve into the aorta. (The aorta is the main artery which takes blood to the body.)
What is mitral regurgitation?
In mitral regurgitation the mitral valve does not close properly. This causes blood to leak back (regurgitate) into the left atrium when the left ventricle squeezes (contracts). Basically, the more open the valve remains, the more blood regurgitates, the more severe the problem.
Causes of mitral regurgitation
Mitral regurgitation can occur if the valve is weakened or damaged. Causes include:
This is the most common cause. The tissues which connect the mitral valves to the heart wall can become weak and stretched over time, which results in the valves not shutting together properly.
Rheumatic heart disease
Rheumatic heart disease (RHD) 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 called the streptococcus. The 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. This can cause permanent damage and lead to thickening and scarring years later. RHD is still quite common in some developing countries
Mitral valve prolapse
In this condition the valve is slightly deformed and bulges back into the left atrium when the ventricle contracts. This can let a small amount of blood leak back into the left atrium. It most commonly occurs in young women. It usually causes no symptoms, as the amount of blood that leaks back is often slight.
Other causes include:
- Hypertrophic cardiomyopathy – a disease where the heart muscle thickens and can distort the mitral valve.
- A heart attack (myocardial infarction)
- Some heart problems present from birth (congenital). It is then usually part of a complex heart deformity.
- Infection of the valve (endocarditis).
- A complication of various other diseases.
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) which 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 is 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 (myocardial infarction).
Complications may occur with mitral regurgitation
- Atrial fibrillation may develop in more severe cases. In this condition the heart beats in a fast and irregular way. The irregular heart rhythm can cause the sensation of a ‘thumping heart’ (palpitations), and make you even more breathless.
- 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.
- 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 than normal valves to infection.) Unless promptly treated, endocarditis can cause serious illness.