Heart Valve Disease

  • Basics

    Heart valve disease is a problem with one or more of the valves that help keep the blood flowing in a forward direction through the heart. It's one of the most common forms of heart disease, affecting about five million Americans. Your heart is a fist-sized muscle that pumps blood through a network of vessels to all parts of your body. It is made up of four chambers: the upper chambers, or the left and right atria, and the lower chambers, or the left and right ventricles. Each chamber is closed off by a valve with thin flaps of tissue (leaflets) that open to allow blood to flow forward, and then close to prevent it from flowing backward.

    Heart valve disease most commonly affects the mitral and the aortic valves, which are located on the left side of the heart. The five most common types of heart valve disease are mitral valve prolapse, mitral stenosis, mitral regurgitation, aortic stenosis, and aortic regurgitation Figure 01.

    Click to enlarge: The Heart and its valves

    Figure 01. The Heart and its valves

  • Causes

    Heart valve disease can result when the valves are damaged or weakened Table 01. The type of heart valve disease that occurs depends on the affected valve and how much bloodflow is disrupted. The forward movement of bloodflow can be affected in two ways: it either builds in a heart chamber when the valve does not open completely (stenosis), or it leaks backwards when the valve does not close completely (regurgitation). A valve can have stenosis and regurgitation at the same time. In all cases, the heart has to work harder to maintain bloodflow. Over time, the extra workload causes the heart to weaken, making it unable to move blood in an efficient manner.

    Mitral valve prolapse (MVP)—also known as the “click-murmur” syndrome because of the sounds it makes through a stethoscope—occurs when the leaflets of the mitral valve become enlarged and can't close properly. When these leaflets are enlarged, they often bulge into the atrium as the heart contracts, disrupting bloodflow. The mitral valve may also become displaced as the fibrous strings supporting the leaflets (chordae) become inflamed and stretched out.

    Although its cause is not known, mitral valve prolapse is generally a condition in which the valve tissues become weak, flabby, and covered with starchlike deposits (myxomatous degeneration).

    Mitral stenosis occurs when the leaflets become scarred, rigid, and covered with hardened tissue and calcium deposits. When this happens, blood can’t flow forward easily, and pressure and fluid build-up are transmitted back to the lungs. This can lead to shortness of breath and, over time, congestive heart failure—a condition where the heart can’t pump adequate amounts of blood. The primary cause of mitral stenosis is rheumatic fever, an autoimmune disease of childhood that begins with strep throat and affects many tissues in the body, especially the heart valves.

    With mitral regurgitation (also called mitral insufficiency), the mitral valve cannot close properly, and blood leaks backward into the left atrium. Mitral regurgitation results when the muscles that control the closing of the valve malfunction, the strings (chordae) that support the leaflets rupture, or when the valve itself degenerates. Mitral valve prolapse, coronary artery disease, buildup of calcium deposits on the valve, injury to the muscles that support the valve, and connective tissue diseases such as lupus or Marfan syndrome or others can also lead to mitral regurgitation.

    Aortic stenosis occurs when the leaflets are misshapen. The aortic valve controls the flow of blood from the left ventricle into the aorta, your body's main artery and blood supplier. When the shape of the aortic valve's leaflets is distorted, the valve narrows, and bloodflow is slowed. About 1 in 20 people are born with only two leaflets instead of the standard three. Known as “bicuspid aortic valve,” this condition can eventually cause aortic stenosis. Although aortic stenosis can also be caused by rheumatic fever, this is rare. The condition is more likely to be caused by age-related degeneration and calcification of the aortic valve, making older people especially prone to aortic stenosis.

    Aortic regurgitation occurs when the valve cannot close properly, and blood leaks back into the left ventricle. Aortic regurgitation can result when the leaflets are deformed, or when the area where the aorta connects to the valve (aortic ring) widens. The two most common causes of leaflet deformity are a bicuspid aortic valve (two leaflets instead of the standard three) and bacterial endocarditis, a serious infection that damages heart valves. The exact cause of aortic ring widening is unknown. However, it may be related to connective tissue disorders, or to ankylosing spondylitis—a condition that causes pain and inflammation in the joints between the spine and pelvis, and between the vertebrae of the spine. Aortic stenosis can also lead to aortic regurgitation.

    Table 1.  Types and Causes of Heart Valve Disease

    Type Definition Cause(s)
    Mitral valve prolapse Tissue flaps of the mitral valve bulge, impairing bloodflow to the left atrium Myxomatous degeneration: a condition that causes valve tissues to become weak and flabby and covered with starch deposits Coronary artery disease Marfan syndrome: a disease of the body's connective tissue that causes joint dislocation and deformity.
    Mitral stenosis A narrowing of the mitral valve that occurs when the leaflets become scarred and rigid. Forward bloodflow is impaired, so pressure and fluid are transmitted back to the lungs. Rheumatic fever: a childhood bacterial infection that begins with strep throat and causes scarring of the valves Connective tissue disorders Tumors
    Mitral regurgitation The mitral valve cannot close properly and blood leaks backward into the left atrium. Rheumatic fever Mitral valve prolapse Coronary artery disease A buildup of calcium deposits on the valve Injury to muscles supporting the valve Connective tissue disease, including lupus and Marfan syndrome, and unknown causes
    Aortic stenosis Valve leaflets are distorted, causing valve narrowing and bloodflow impairment. Bicuspid aortic valve: (only two valve leaflets instead of the normal three) Calcium deposits and fibrous tissue buildup on leaflets Rheumatic fever
    Aortic regurgitation Valve cannot close properly, and blood leaks back into the left ventricle. Bicuspid aortic valve Endocarditis (an infection that causes the lining of the heart and valves to become inflamed) Rheumatic fever Connective tissue disorders Aortic stenosis

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