Mitral (MI-tral) valve prolapse (MVP) is a condition in which one of the heart's valves, the mitral valve, doesn't work properly. The flaps of the valve are "floppy" and don't close tightly.
Much of the time, MVP doesn't cause any problems. Rarely, blood can leak the wrong way through the floppy valve, which may cause shortness of breath, palpitations (strong or rapid heartbeats), chest pain, and other symptoms.
In MVP, when the left ventricle contracts, one or both flaps of the mitral valve flop or bulge back (prolapse) into the left atrium. This can prevent the valve from forming a tight seal.
As a result, blood may flow backward from the ventricle into the atrium. The backflow of blood is called regurgitation (re-GUR-ji-TA-shun).
Backflow doesn't occur in all cases of MVP. In fact, most people who have MVP don't have backflow and never have any symptoms or complications. In these people, even though the valve flaps prolapse, the valve still can form a tight seal.
When backflow does occur, it can cause symptoms and complications such as shortness of breath, arrhythmias (ah-RITH-me-ahs), or chest pain. Arrhythmias are problems with the rate or rhythm of the heartbeat.
This answer from the National Heart, Lung and Blood Institute has been reviewed and/or edited by Dr. William D. Knopf.