Patient information: Mitral regurgitation

MITRAL REGURGITATION OVERVIEW

Mitral regurgitation (MR), which is also known as mitral insufficiency, is a common heart valve disorder. When mitral regurgitation is present, blood flows backwards through the mitral valve when the heart contracts. This reduces the amount of blood that is pumped out to the body.

This topic review discusses the causes, signs and symptoms, diagnosis, and treatment options for people with mitral regurgitation.

HEART FUNCTION

Normal heart — The heart is a pump that contains four chambers: the right atrium, right ventricle, left atrium, and left ventricle (figure 1). Blood returning to the heart flows into the right atrium, and then the right ventricle. Blood is pumped out of the right ventricle into the lungs, where oxygen is added. Blood then returns to the heart through the left atrium. Blood in the left atrium flows into the left ventricle, which pumps the blood to the rest of the body through the aorta.

The heart normally contracts and relaxes in a rhythmic fashion. This action causes changes in pressure within the heart that allow the heart to fill with blood (during relaxation) and to pump blood forward to the body (during contraction).

There are four valves in the heart:

• Two valves separate the upper and lower chambers: one on the right (tricuspid valve) and one on the left side of the heart (mitral valve, (figure 1).
• Two valves separate the heart from the blood vessels: one is between the heart and the lungs (pulmonic valve) and other is between the heart and the aorta (aortic valve).

These valves consist of flaps called leaflets or cusps that open and close to help ensure the continued forward flow of blood through the heart.

Mitral regurgitation — When mitral regurgitation is present, blood leaks backwards through the mitral valve and into the left atrium when the heart contracts. This means that less blood is pumped out of the heart to supply the body. If the amount of MR is small and does not progress, the backward leak has no significant consequences.

If significant (moderate to severe) regurgitation is present, the left ventricle must work harder to keep up with the body's demands for oxygenated blood. Over time, the heart muscle (the myocardium) and circulatory system undergo a series of changes to maintain this increased demand. These changes generally occur in phases over many years, even decades, depending upon the amount of blood that is regurgitated and how the heart responds to the regurgitated blood. The cause of mitral regurgitation also determines how quickly the heart begins to fail.

Compensated phase — The major change during this phase is enlargement of the left ventricle. This is known as the compensated phase, which does not usually cause symptoms, the heart rhythm is usually normal, and surgical treatment is generally not required.

Transitional phase — As mitral regurgitation progresses, the heart muscle (myocardium) begins to fail because the ventricle can no longer compensate for the regurgitation. This phase is called the transitional phase. The reason that you might progress from the compensated to the transitional phase is not completely clear, although changes in heart or heart pumping function may occur as progressively greater volumes of blood are regurgitated and/or the size of the left ventricle increases.

You may experience fatigue, have a decreased ability to exercise or be active, or feel short of breath in the transitional phase. However, some people have no symptoms. Surgical treatment is usually recommended when you enter the transitional phase. (See 'Surgical treatment' below.)

Decompensated phase — As the left ventricle enlarges and functions less efficiently, the left atrium progressively enlarges, abnormal heart rhythms occur, and the blood pressure in the pulmonary artery (the blood vessel from the heart to the lungs) increases; this is called pulmonary hypertension. Over time, these changes become irreversible as the signs and symptoms of heart failure develop. (See "Patient information: Heart failure causes, symptoms, and diagnosis".)

MITRAL REGURGITATION CAUSES

A trivial amount of mitral regurgitation is present in up to 70 percent of adults. Significant (moderate to severe) mitral regurgitation is much less common. For example, moderate or severe mitral regurgitation was found in only about 2 percent of people in one study [1]. Significant mitral regurgitation can develop as a result of an abnormality in a heart valve or another cardiac disease, including the following:

• Mitral valve prolapse — Mitral valve prolapse occurs when the mitral valve leaflet tissue is deformed and elongated so that the leaflets do not come together normally. This abnormal valve motion may allow blood to leak backwards from the left ventricle into the left atrium. Although most people with mitral valve prolapse have only trace or mild mitral regurgitation, some develop significant mitral regurgitation.
• Infective endocarditis — Infective endocarditis (IE) is an infection of the heart valves caused by bacteria, fungi, or other organisms that invade the bloodstream. As the microorganisms adhere to the valves and grow, abnormal structures (known as vegetations) develop on the heart valves. The vegetation can prevent the mitral valve from closing normally, allowing blood to regurgitate. A heart valve that is already abnormal is more likely to develop endocarditis compared to a valve that is normal.
• Rheumatic fever — Rheumatic fever is a bodywide illness that occurs when the bacterium that causes Strep throat (group A Streptococcus) is not treated. Rheumatic fever causes inflammation of the valves of the heart, as well as other complications. Rheumatic fever is now uncommon in developed countries, although it still occurs commonly in developing countries.
• Congenital heart abnormality — Children who are born with certain types of heart abnormalities can develop mitral regurgitation.
• Other types of heart disease — Mitral regurgitation can develop as a result of other types of heart diseases, such as after a heart attack or other cause of heart muscle injury.
• Trauma — Chest trauma can rarely cause breakage of the chords that hold the mitral leaflets in their normal position. Untethered leaflets swing widely, allowing valve leakage.

MITRAL REGURGITATION SIGNS AND SYMPTOMS

Most people with mitral regurgitation have no symptoms. People with mild to moderate mitral regurgitation may never develop symptoms or serious complications.

Even in people with severe mitral regurgitation, there may be no signs or symptoms until the left ventricle fails, an abnormal heart rhythm develops (atrial fibrillation), or pulmonary hypertension occurs. Pulmonary hypertension occurs when the blood pressure in the pulmonary artery is increased. This increases the workload of the right side of the heart, making it difficult to provide an adequate amount of oxygenated blood to the body.

People with severe disease and left ventricular enlargement may eventually develop signs and symptoms of heart failure, which include weakness and fatigue, shortness of breath with exertion and/or at rest, or edema (abnormal fluid collection in the lower legs or abdomen). (See "Patient information: Heart failure causes, symptoms, and diagnosis".)

MITRAL REGURGITATION DIAGNOSIS

You may be diagnosed with mitral regurgitation after your healthcare provider listens to your heart with a stethoscope and hears a heart murmur. The murmur is caused by the sound of turbulent blood flowing backwards through the mitral valve.

A heart murmur may occur as a result of one or more conditions; to determine the cause of the murmur, one or more diagnostic tests may be recommended.

Electrocardiogram (ECG) — An ECG provides a picture of the electrical activity that causes the heart to beat. An ECG may detect rhythm disturbances or evidence of coronary artery disease or other conditions that can cause mitral regurgitation. It can also show evidence of other associated cardiac abnormalities.

Chest x-ray — A chest x-ray shows the size and shape of the heart and the large blood vessels in the chest. It also can identify fluid accumulation in the lungs. Many people with significant mitral regurgitation have an enlarged heart (picture 1).

Echocardiogram — An echocardiogram uses ultrasound (high frequency sound waves) to assess the size of the heart's chambers, the movement of the heart valves, and the size and motion of the heart wall. It can also measure the cardiac output (the volume of blood pumped in one minute) and the pressures within various chambers of the heart and the major blood vessels to and from the heart.

In most cases, the echocardiogram is done by pressing a smooth probe against the skin of the chest or abdomen. Gel is applied to the chest to help the wand glide against the skin and allow the sound waves to travel through the chest more easily. This type of echocardiogram is called a transthoracic echocardiogram.

If the images of the heart are not clear with transthoracic echocardiography, a transesophageal echocardiogram (TEE) may be recommended. With TEE, you are given sedative medication and the probe is inserted into your mouth and passed down the esophagus. This allows the physician to have a closer view of your heart valves and other structures.

LIVING WITH SIGNIFICANT MITRAL REGURGITATION

Monitoring over time — People with trivial or mild mitral regurgitation do not require routine monitoring of their condition. People with significant (moderate to severe) mitral regurgitation should have routine monitoring to determine if and when treatment is needed [2]. The frequency of monitoring depends upon several factors, including the severity of the mitral regurgitation (measured by echocardiogram, (table 1), the size and function of the left ventricle, and the presence of symptoms.

• People with moderate mitral regurgitation are usually seen once per year, or sooner if symptoms develop.
• People with severe mitral regurgitation are usually seen every 6 to 12 months, or sooner if symptoms develop.

Physical exercise — The 2006 American College of Cardiology/American Heart Association guidelines concluded that no exercise restrictions are needed for people who have the following [2]:

• No symptoms of mitral regurgitation
• A normal heart rhythm
• Normal size left ventricle and left atrium
• Normal pulmonary artery pressure

Your healthcare provider can help to determine if you should exercise or participate in sports if you have one or more of the above [3].

Mitral regurgitation and pregnancy — Women with chronic mitral regurgitation usually have no increased risks as a result of pregnancy, especially if mitral regurgitation is mild or moderate and there are mild or no symptoms [4].

In contrast, women with moderate to severe symptoms and other complications of mitral regurgitation have a high risk of developing complications during pregnancy. Women with mitral regurgitation should talk to their cardiologist about the risks and benefits of pregnancy and the possibility of having valve repair or replacement surgery before trying to become pregnant. Valve repair or replacement surgery is not recommended during pregnancy except in emergency situations.

Presence of atrial fibrillation — People with chronic mitral regurgitation often develop an abnormal heart rhythm called atrial fibrillation (AF). In AF, rapid, chaotic electrical impulses cause the heart to "quiver" ineffectively rather than beat in coordinated contractions. AF can reduce the amount of blood being pumped out to the body; this is of particular concern in people with mitral regurgitation because the heart already has a decreased ability to pump blood out. In addition, atrial fibrillation increases the risk of experiencing a stroke.

People with mitral regurgitation who develop atrial fibrillation are usually treated with a medication to prevent blood clots and may be given a treatment to normalize the heart rhythm. This is discussed in a separate article. (See "Patient information: Atrial fibrillation".)

After the initial treatment of atrial fibrillation, people with mitral regurgitation are often encouraged to have valve repair or replacement before the left atrium enlarges substantially. Delaying surgical repair may make it more difficult to reverse atrial fibrillation to a normal heart rhythm. In people with mitral regurgitation, chronic atrial fibrillation significantly increases the chance of developing a blood clot (thrombus) that can break off (embolus) and lodge in an artery in the brain (causing a stroke) or somewhere else in the body. (See "Patient information: Stroke symptoms and diagnosis" and "Patient information: Pulmonary embolism".)

MITRAL REGURGITATION TREATMENT

The need for treatment of mitral regurgitation depends upon the presence and severity of symptoms, the cause of the mitral regurgitation, and the presence of other underlying medical conditions. People with mild or moderate mitral regurgitation may not require any specific treatment.

Medical and surgical therapies are available to treat people with mitral regurgitation. The treatment of choice for most people with severe chronic mitral regurgitation is surgical repair or replacement of the mitral valve. However, in some cases, surgical treatment may be delayed or deferred due to the presence of other medical conditions that increase the risk of surgery.

Surgical treatment — Surgery is required only for people with severe mitral regurgitation. Guidelines from the American Heart Association and European Society of Cardiology define a person as having severe chronic mitral regurgitation based upon echocardiogram measurements of the heart, heart valves, and blood flow (algorithm 1A-B) [2,5].

Surgical treatment may include either repair of your own mitral valve or replacement of the valve. The choice of procedure depends, at least in part, upon the cause of the mitral regurgitation, the anatomy of your mitral valve, and the performance of the left ventricle.

The procedure — Valve repair or replacement surgery is done in an operating room after you are given general anesthesia. With the traditional approach, the surgeon makes an incision in the breastbone (sternum), called a median sternotomy, to open the chest and gain access to the heart. Other approaches, which do not involve cutting the sternum, are available, although there are fewer data regarding the safety and efficacy of these newer techniques.

To repair or replace the valve, the heart must be stopped temporarily. While the heart is stopped, a heart-lung machine (cardiopulmonary bypass machine) functions like the heart and lungs, circulating blood and providing oxygen to the body. Fluids, nutrients, and medications may be added to the blood while it passes through the cardiopulmonary bypass machine. The procedure generally lasts between two and four hours.

Valve repair — If the mitral valve can be repaired, this is generally preferred to mitral valve replacement. Advantages of repair include improved ventricular function compared to valve replacement surgery. In addition, people who have valve repair do not require lifelong treatment with an anticoagulant (blood thinner).

During valve repair, the surgeon will reshape the valve to prevent or reduce the backwards flow of blood (figure 1).

Valve replacement — If valve replacement is necessary, the replacement valve may be mechanical (made from metal) or bioprosthetic (made from biologic materials such as a pig valve). Mechanical valves have the disadvantage of requiring lifelong treatment with a medication to prevent blood clots (warfarin [Coumadin®]), while bioprosthetic valves have the disadvantage of potentially wearing out and requiring replacement earlier, particularly in people under age 65. People who are in atrial fibrillation often need lifelong anticoagulation, regardless of which valve type is used.

When deciding between a mechanical and bioprosthetic heart valve, it is important for you and your physician to consider the risks of warfarin therapy compared to the potential need for a repeat valve replacement. The use of warfarin is discussed in detail in a separate article. (See "Patient information: Warfarin (Coumadin®)".)

Guidelines from the American College of Cardiology and American Heart Association in 2006 recommend the following [2]:

• Bioprosthetic valves are recommended for people who cannot or will not take warfarin.
• A mechanical valve is usually recommended for people under age 65 who have long-standing atrial fibrillation.
• A bioprosthetic valve is usually recommended for people who are 65 years or older.
• A bioprosthetic valve is a reasonable option for people under age 65 who have a normal heart rhythm. However, the patient and physician must have a detailed discussion of the risks of warfarin compared to the likely need for repeat valve replacement in the future.

Maze procedure — When people with mitral regurgitation and atrial fibrillation have valve surgery, an additional procedure (called the maze procedure) is often done to reduce the likelihood of long term atrial fibrillation. During the procedure, several small incisions are made in the left atria to interrupt the electrical pathways that allow atrial fibrillation to occur. The decision to perform a maze procedure is based upon the person's age and other factors because it does increase the length of the operation.

Recovery from surgery — Most patients are able to leave the hospital within 5 to 6 days after surgery. Some people are able to be discharged after 4 days, while others may require a longer stay, especially if complications (eg, bleeding, infection) develop.

Depending upon your occupation, you will probably be able to return to work within two months after discharge from the hospital. Some people are able to return to work after one month while others may require up to three months to feel well enough to return.

You will generally sees your surgeon approximately one week after surgery and your cardiologist one to two weeks later. A postoperative echocardiogram (and sometimes an EKG) are usually performed at that time.

Treatment with medications — One or more medications may be recommended for some people with mitral regurgitation to relieve the signs and symptoms of heart failure, reduce the workload of the heart, or prevent complications such as blood clots or infections. Treatment of heart failure is discussed in detail in a separate topic review. (See "Patient information: Heart failure treatments".)

Vasodilators — Vasodilators such as nitroprusside, hydralazine, and angiotensin converting enzyme (ACE) inhibitors enlarge (dilate) the blood vessels, which can improve circulation. However, it is not clear that there is a benefit of long-term treatment of chronic mitral regurgitation with vasodilators.

As a result, vasodilators are usually reserved as a short term treatment of people with severe mitral regurgitation who are hospitalized. Vasodilators may also be recommended as a long-term treatment if you cannot have valve repair or replacement surgery (eg, due to a serious underlying medical condition).

Anticoagulants — Anticoagulants such as warfarin are used to prevent blood clots. Lifelong treatment with warfarin (Coumadin®) is recommended for certain people with chronic mitral regurgitation, including those with atrial fibrillation or a mechanical heart valve. (See "Patient information: Warfarin (Coumadin®)".)

Preventive antibiotic treatments — Infective endocarditis is a bacterial infection that causes the heart valves to become inflamed. The guidelines for preventing infective endocarditis with antibiotics have been updated [6]. As a result, people with mitral regurgitation who have NOT undergone heart valve surgery do NOT require preventive antibiotic treatment before dental and surgical procedures.

In contrast, people who have a mechanical or bioprosthetic replacement mitral valve or who have prosthetic material used to repair the mitral valve SHOULD have antibiotic treatment before dental, oral, or upper respiratory tract procedures to reduce the risk of developing infective endocarditis. This is discussed in detail in a separate article. (See "Patient information: Antibiotics before procedures".)

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:
Patient information: Heart failure causes, symptoms, and diagnosis
Patient information: Atrial fibrillation
Patient information: Stroke symptoms and diagnosis
Patient information: Pulmonary embolism
Patient information: Warfarin (Coumadin®)
Patient information: Heart failure treatments
Patient information: Antibiotics before procedures

Professional Level Information:
Arrhythmic complications of mitral valve prolapse
Echocardiographic evaluation of the mitral valve
Etiology, clinical features, and evaluation of chronic mitral regurgitation
Functional mitral regurgitation
Indications for corrective surgery in severe chronic mitral regurgitation
Ischemic mitral regurgitation
Natural history of chronic mitral regurgitation in mitral valve prolapse and flail mitral leaflet
Overview of the management of chronic mitral regurgitation
Pathophysiology and stages of chronic mitral regurgitation
Pathophysiology, clinical features, and management of acute mitral regurgitation
Transesophageal echocardiography in the evaluation of mitral valve disease
Valvular heart disease in elderly adults
Vasodilator therapy in chronic mitral regurgitation

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/ency/article/000176.htm)

• National Heart, Lung, and Blood Institute

      (www.nhlbi.nih.gov)

• American Heart Association

      (www.americanheart.org)

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