Mitral valve prolapse is a malfunction of the heart's mitral valve, the physical doorway between the heart's left atrium and left ventricle. Normally, the mitral valve closes when the ventricle's muscles contract, preventing blood from flowing back into the left atrium when the heart pumps blood to the rest of the body. In mitral valve prolapse, however, a slight deformity of the mitral valve prevents the valve from closing normally. This appears as an abnormal floppiness, or prolapse, of the valve. The result is that small amounts of blood leak back into the left atrium, with very little effect on the heart's overall ability to pump blood.
In some people, the leak worsens to create a significant backflow of blood into the left atrium. This is called mitral regurgitation. People with severe mitral regurgitation can develop symptoms such as shortness of breath, fatigue and leg swelling. Rarely, heart surgery is needed to repair the damaged valve.
In most people with mitral valve prolapse, the cause is unknown. However, in a small number of patients, mitral valve prolapse may be related to another medical condition, such as an inherited abnormality in the way the body produces collagen (connective tissue) or rheumatic heart disease (a rare complication of strep throat).
Health experts estimate that mitral valve prolapse currently affects up to 5% of people in the United States. For unknown reasons, the condition is most common in women between 14 and 30. The condition sometimes affects several members of the same family,and there is some evidence that the condition can be inherited.