Mitral regurgitation occurs when some blood leaks or is forced back the wrong direction through the mitral valve when the heart beats. This can come from a weak heart valve, or one that is slightly too large and may "flop" when it closes. Mitral stenosis is a blockage of the valve, where it is too small and blood has trouble flowing forward through it into the heart's chamber. This can be genetic, but can also be caused by calcification of the valve and/or heart disease.
