Congenital: Mitral valve stenosis is sometimes seen in babies born with deformities in the mitral valve structure or subvalvular apparatus. Some of the pathological conditions are
Double orifice mitral valve- the mitral valve opening is divided into two by an abnormal tissue; or there is an extra opening in the mitral valve leaflets; or two mitral valves with its own annulus, leaflets, chordae tendinae and papillary muscles are present. Among these three, the accessory hole type is the most common and the duplicate valve is the least common type. 50% of the patients with this defect have normal mitral valve function.
Parachute mitral valve – The chordae are thick and short and regardless to its leaflets they are attached to one or two papillary muscles only. The valve resembles a parachute’s canopy.
Fusion of the commissures- when there is a fusion of the mitral valve commissures, it leads to an obstruction in the blood flow to the left ventricle. Further calcification can result in increased resistance to the flow.
These anomalies often are associated with one or more of other congenital defects like supravalvular mitral ring, aortic stenosis, coarctation of aorta, atrial septal defect, ventricular septal defect and left ventricular hypoplasia. Together they are called “Shone’s complex”. In this condition blood flow to and from the left ventricle is compromised.