What causes a leaky mitral valve?

Some people are born with a faulty mitral valve. But most acquire the problem in response to a different heart ailment.

Of the four valves that orchestrate the flow of blood through your heart, one of them — the mitral valve — is a bit more intricate than the others. Located within the left side of the heart, the mitral valve opens to allow oxygen-rich blood from the upper chamber (atrium) to flow down into the lower chamber (ventricle). After the powerful left ventricle contracts, the two leaflets of the mitral valve snap shut, preventing blood from flowing backward into the left atrium.

That action requires all the nearby structures to work well together: the strands of tissue (chordae) and papillary muscles that tether the valve in place, the fibrous ring of tissue attached to the leaflets (annulus), and the left ventricle (see illustration).