Mitral Regurgitation, Chronic
Chronic mitral regurgitation occurs when the mitral valve in the heart fails to close tightly. This allows some oxygen-rich blood to flow back into the heart rather than out into the body.
What is going on in the body?
The left side of the heart has two chambers:
- the left atrium
- the left ventricle
Between them lies the mitral valve, a one-way valve that allows blood to flow from the left atrium to the left ventricle, the main pumping chamber of the heart. The mitral valve opens to allow the ventricle to fill. It closes as the ventricle contracts and the ventricle ejects oxygen-rich blood into the aorta, the major artery in the body. This blood is then sent throughout the body.
If the mitral valve fails to close tightly, some blood is pumped back into the atrium when the ventricle contracts. This reduces the flow of blood to the rest of the body.
The left ventricle then pumps harder to compensate for the decreased blood flow. The build-up of blood in the left atrium puts pressure on the lungs and a chamber on the right side of the heart called the right ventricle. This can cause right ventricular failure.
Elderly people often have minor problems or minor regurgitation in the mitral valve. Such problems cause little or no heart trouble. With larger mitral valve defects, though, the left atrium and ventricle enlarge over time. Congestive heart failure and abnormal heart rhythms, or arrhythmias, can follow.
What are the causes and risks of the condition?
A wide variety of conditions can cause mitral regurgitation. Generally speaking, any condition that changes the shape, structure, or function of the mitral valve or its attachments to the heart can cause this condition. These include:
- heart attacks
- heart tumor
- congenital heart disease, or a disorder present at birth
- autoimmune disease, or one in which the body attacks its own cells
- rheumatic fever
- mitral valve prolapse
Irregular heart rhythms, or arrhythmias, may be due to enlargement of the left atrium.
What can be done to prevent the condition?
Prompt treatment of any underlying heart disease may reduce the risk of mitral regurgitation. Sometimes, though, nothing can be done to prevent the condition.
How is the condition diagnosed?
Chest x-rays can reveal an enlarged left atrium and ventricle. The patterns traced during an ECG, or electrocardiogram, a test that records the electrical activity of the heart, can indicate an enlarged left atrium and strain in the left ventricle. Arrhythmias due to the enlarging atrium are common findings on an ECG.
Ultrasound tests, such as echocardiography and color Doppler studies, use sound waves to create images of organs and blood flow. These tests visualize the amount of damage to the valve and the amount of blood flowing through it. This helps a doctor decide whether the valve damage is significant. Blood clots in the atrium can be detected with a special test called transesophageal echocardiography.
Long Term Effects
What are the long-term effects of the condition?
Long-term effects depend on the severity of the regurgitation.
In severe cases, heart failure occurs and surgery may be necessary. People with this condition have a higher risk of heart infections. They need to take antibiotics before surgery and dental procedures.
People with severe heart failure and those with atrial fibrillation, a rapid irregular atrial rhythm, have a higher risk of blood clots. Blood clots can travel from the atrium to block the flow of blood to an organ. For example, a blood clot can travel to the brain and cause a stroke.
What are the risks to others?
There are no risks to others.
What are the treatments for the condition?
If the problem is mild, nothing need be done. Otherwise, the following treatments may be used as needed:
- Blood thinning drugs reduce the risk of blood clots in people with atrial fibrillation.
- Heart medications can help relieve pressure throughout the system and control abnormal heart rhythms.
- Heart valve surgery to repair the mitral valve helps relieve symptoms.
- Surgical replacement of the valve is needed when severe mitral regurgitation has caused heart failure. This prevents further damage to the left ventricle.
Some people are poor candidates for surgery because of permanent changes to the blood vessels in the lungs. Heart medications to improve the hearts function is needed to prepare these people for surgery.
What are the side effects of the treatments?
Some artificial valves raise the risk for blood clots. As with any surgery, the risks include:
What happens after treatment for the condition?
After surgery, the surgical site is monitored for bleeding. A patient may be on a monitor to watch for the occurrence of post-operative arrhythmias. A person can gradually return to normal daily activities. A healthy diet which includes sodium restriction, and a slow return to exercise programs are advised.
How is the condition monitored?
Artificial valves wear out over a period of years and may need to be replaced. Echocardiography tests may be done to assess the condition of the valve after it is repaired or replaced.
Merck Manual, 1999
Current Medical Diagnosis and Therapy,1996
Harrison's: Principles of Internal Medicine, 1991