The mitral valve is the heart valve between the left atrium and left ventricle. It has two flaps or cusps. In mitral valve prolapse (MVP), one or both mitral valve flaps are enlarged and some of their supporting "strings" may be too long. When the heart contracts or pumps, the mitral valve flaps do not close smoothly or evenly. Instead, part of one or both flaps collapses backward into the left atrium. This sometimes allows a small amount of blood to leak backward through the valve and may cause a heart murmur.

Mitral valve prolapse is also known as click-murmur syndrome, Barlow's syndrome, balloon mitral valve and floppy valve syndrome. The majority of patients with mitral valve prolapse have no symptoms, will have no problems and, therefore, will need no treatment. However, those who have leaky or regurgitant prolapsing valves will need antibiotics to prevent infection (endocarditis) of the valve during certain surgical or dental procedures that are likely to cause bleeding. In addition, medicine may be used in a small number of MVP patients with chest pain, angina pectoris or abnormal heart rhythms (arrhythmia's).

See American Heart Association for more information on Mitral Valve Prolapse.