The mitral valve is the valve between the left upper and left lower chambers (left atrium and left ventricle) of the heart. Mitral valve prolapse syndrome (MVP) is a common condition in which one or both of the flaps (cusps) of the mitral valve bulge or collapse backward (prolapse) into the left atrium during ventricular contraction (systole). In some cases, this may allow leakage or the backward flow of blood from the left ventricle back into the left atrium (mitral regurgitation).
The exact underlying mechanism responsible for MVP remains unknown. In many affected individuals, the condition appears to occur in the absence of an associated disorder or syndrome (idiopathic). Evidence indicates that the condition is sometimes familial, suggesting autosomal dominant inheritance. In other cases, MVP occurs in association with certain inherited connective tissue diseases, other heart abnormalities, or other underlying conditions, disorders, or syndromes.
In many individuals with MVP, no associated symptoms are apparent (asymptomatic). However, in other cases, the condition may result in chest pain, abnormal heart rhythms (arrhythmias), fatigue, dizziness, and/or other symptoms and signs. MVP is often associated with a characteristic click and/or a subsequent delayed murmur that may be detected through use of a stethoscope during physical examination.
In many individuals with mitral valve prolapse syndrome (MVP), no symptoms are apparent (asymptomatic) and the condition is often nonprogressive. However, others with MVP may develop fatigue, difficulty breathing (dyspnea) with exertion, awareness of the heart beat and a “pounding” or racing of the heart (palpitations), and abnormal heart rhythms (arrhythmias). Additional signs may include lightheadedness, fainting episodes (syncope), abnormally low blood pressure upon standing (orthostatic hypotension), headaches, chest pain, and/or other symptoms and findings.
In rare cases, MVP may lead to heart failure or impaired ability of the heart to pump blood effectively to the lungs and on to the rest of the body due to severe mitral regurgitation; the formation of blood clots; transient ischemic attacks (TIAs) or stroke; and/or sudden potentially life-threatening complications. (TIAs are characterized by temporary impairment of brain function due to brief interruptions of blood supply. A stroke refers to localized death of brain tissue [cerebral infarction] due to lack of blood flow and insufficient oxygen supply to the brain. TIAs or stroke may result from interruption of the brain’s blood supply by a blood clot carried in the bloodstream [embolism].)
Individuals with MVP associated with mitral regurgitation may have an increased risk of developing bacterial infections of the heart lining and valves (bacterial endocarditis). (For further information, please see the “Standard Therapies” section of this report below.)
The specific underlying mechanism responsible for mitral valve prolapse syndrome (MVP) is unknown. However, evidence indicates that various changes of the mitral valve or the lower left chamber of the heart (left ventricle) may lead to MVP. Such abnormalities may include excessive or redundant mitral valve flap (cusp) tissue and/or elongation of the strands of tendon (chordae tendinea) that anchor the cusps to certain muscles (papillary muscles) of the ventricle.
In many affected individuals, MVP appears to occur as an isolated condition in the absence of an associated disorder or syndrome (idiopathic). In addition, according to experts, there appears to be an increased frequency of the condition in some families, suggesting an autosomal dominant mode of inheritance. Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother.
In autosomal dominant disorders, a single copy of the disease gene (received from either the mother or father) may be expressed “dominating” the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child. The risk is the same for each pregnancy.
In other affected individuals, the changes associated with MVP may occur with various underlying conditions or syndromes, including certain inherited connective tissue disorders, such as Marfan syndrome, Ehlers-Danlos syndrome (EDS), or osteogenesis imperfecta (OI); particular heart (cardiac) abnormalities; or other disorders. Marfan syndrome, an autosomal dominant disorder, may be characterized by cardiac, blood vessel, musculoskeletal, and eye abnormalities. EDS refers to a group of genetic disorders characterized by abnormally flexible, easily dislocated joints; unusually loose, thin, “stretchy” (elastic) skin; and excessive tissue fragility. OI is an autosomal dominant disorder in which defective development of connective tissue may result in abnormally brittle, fragile bones; recurrent fractures; abnormal thinness of the white outer coat of the eyes, causing them to appear blue (blue sclerae); and other associated findings. (For further information on these disorders, choose “Marfan,” “Ehlers Danlos,” or “osteogenesis imperfecta” as your search term in the Rare Disease Database.)
Cardiac abnormalities potentially associated with MVP may include disease of heart muscle (cardiomyopathy); heart malfunction or damage due to narrowing or blockage of the arteries supplying heart muscle (coronary artery disease); an abnormal opening in the fibrous partition (septum) that normally separates the two upper heart chambers (i.e., certain atrial septal defects); rheumatic heart disease; or other conditions. Rheumatic heart disease is damage to heart muscle and heart valves caused by acute rheumatic fever, an inflammatory disease that may occur as a delayed reaction to infection with streptococcal bacteria (i.e., group A beta-hemolytic streptococci). (For further information, please choose “rheumatic fever” as your search term in the Rare Disease Database.)
Although mitral valve prolapse syndrome (MVP) has been reported in individuals of various ages, it is most commonly noted in young adults. Estimates indicate that MVP affects approximately four to eight percent of young adults in the general population, with females affected more commonly than males.
Mitral valve prolapse syndrome (MVP) may be diagnosed based upon thorough clinical examination, a complete patient and family history, and various tests. The condition is often recognized through use of a stethoscope during routine physical examination, based upon detection of a characteristic clicking sound or sounds (systolic clicks) and/or a subsequent, delayed, high-pitched murmur (late systolic regurgitation murmur). The diagnosis may be confirmed based upon specialized imaging techniques, particularly echocardiography, during which sound waves are directed toward the heart, enabling physicians to identify abnormal positioning and prolapse of the mitral valve flaps. In some cases, additional cardiac and other diagnostic studies may be recommended to help confirm and assess the severity of potentially associated abnormalities, such as accompanying regurgitation.
The treatment of MVP is directed toward the specific symptoms that are apparent. Most individuals with MVP have no associated symptoms and require no treatment. However, as mentioned above, those with associated mitral regurgitation may have an increased risk of developing bacterial infections of the heart lining and valves (bacterial endocarditis). Therefore, appropriate antibiotic therapy (antibiotic prophylaxis) is required prior to dental procedures, surgical procedures, and certain diagnostic techniques to help prevent such infection.
In some cases, treatment with certain medications (e.g., beta blockers) may be recommended for those with associated chest pain, headaches, dizziness, or certain other findings. In addition, antiarrhythmic agents may be administered for those with symptoms due to abnormal heart rhythms.
In rare cases, if affected individuals have severe mitral regurgitation, surgical mitral valve repair or replacement may be required. For those who experience transient ischemic attacks, disease management may include the use of aspirin or appropriate anticlotting (anticoagulant) agents. Other treatment for this disorder is symptomatic and supportive.
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FROM THE INTERNET
Online Mendelian Inheritance in Man, OMIM (TM). John Hopkins University, Baltimore, MD. MIM Number 157700; 11/22/99. Available at: http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?157700.
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