Mitral stenosis anatomy


 * Associate Editor-In-Chief: Mohammed A. Sbeih, M.D.[mailto:msbeih@perfuse.org];

Overview
The normal mitral valve orifice area is 4-6 cm2. Mitral stenosis occurs when the orifice area is reduced to at least 2.2 cm2. This degree of narrowing results in a gradient across the mitral valve.

Anatomy
The opening is surrounded by a fibrous ring known as the mitral valve annulus. The anterior cusp covers approximately two-thirds of the valve area (imagine a crescent moon within the circle, where the crescent represents the posterior cusp). These valve leaflets are prevented from prolapsing into the left atrium by the action of tendons attached to the posterior surface of the valve, the chordae tendineae.

The inelastic chordae tendineae are attached at one end to the papillary muscles and at the other end to the valve cusps. Papillary muscles are fingerlike projections that extend from the wall of the left ventricle. Chordae tendineae from each muscle are attached to both leaflets of the mitral valve. Thus, when the left ventricle contracts, the intraventricular pressure forces the valve to close, while the tendons keep the leaflets coapting together and prevent the valve from opening in the wrong direction; thus preventing blood to flow back to the left atrium. Each chord has a different thickness. The thinnest ones are attached to the free leaflet margin, whereas thickest ones are attached quite away from the free margin. This disposition has important effects on systolic stress distribution physiology.