Mitral valve prolapse is a valvular condition of the heart. It occurs when a mitral valve flap turns into the left atrium during systole, causing blood to flow back from the left ventricle to the left atrium. This happens when one or both flaps (or leaflets) of the mitral valve are abnormally thickened. Mitral valve prolapse can cause mitral regurgitation, congestive heart failure, and endocarditis. Mitral valve prolapse is classified as classic and nonclassic.
In order to be able to effectively diagnose mitral valve prolapse, one has to resort to echocardiography, which uses ultrasound to visualize the mitral valve. Early studies wrongly estimated a prevalence of 38% among healthy teenage males. Nevertheless, using echocardiography, it has been discovered that it really affects only 2-3% of the general population, and it is most often diagnosed in people aged 20-40 years. Some people may inherit the condition, which is associated with connective tissue disorders like Marfan syndrome.