Some parts of your valve may fail
Some diseases will affect the normal function of the mitral valve. Rheumatic fever will stiffen the leaflets, sometimes all the way to ‘calcification’, degenerative disease usually will cause failure of the support of the leaflets and cause them to ‘prolapse’ with a regurgitation of blood to the lungs as a result.
This will lead to overfilling of the pulmonary tissue and shortness of breath on exertion.
These phenomena will invariably lead to a ‘cascade’ of bad consequences as dilation of the left atrium, strain on its wall, rhythm disturbances and high pressures on the right side of the heart and last but not least compromise of the left ventricular contractile reserve.