Mitral Valve Apparatus Anatomy and Function

Structural Components

The mitral valve apparatus is a complex, coordinated structure consisting of the saddle-shaped annulus, multiscalloped leaflets connected by commissures, chordae tendineae, papillary muscles, and left ventricular wall attachments, all working together to ensure unidirectional blood flow from the left atrium to the left ventricle 1, 2, 3
The mitral annulus is a hyperbolic paraboloid (saddle-shaped) structure that serves as the attachment point for the mitral valve leaflets 1
The mitral annulus is oval in shape, which cannot be adequately appreciated with 2D echocardiography alone 3
The mitral valve has two asymmetric leaflets: anterior and posterior, with the anterior leaflet having a larger radial surface despite being attached to only about one-third of the annular circumference 1
The anterior leaflet is sail-shaped and in continuity with the left and noncoronary cusps of the aortic valve (aortic-mitral curtain) 1, 5
Both leaflets are segmented into three individual scallops 1, 6
The chordae tendineae are classified based on their insertion points on the leaflets, with primary, secondary, and tertiary chordae 1, 3, 5
The papillary muscles, including the anterolateral and posteromedial papillary muscles, attach to the left ventricular wall and work in coordination with the chordae to prevent valve prolapse during systole 1, 5

The mitral valve apparatus requires intricate coordination between all anatomic components, each with unique functional geometry 1
Normal valve function depends on the complex interaction between the leaflets, subvalvular apparatus, annulus, and left ventricle 6
During systole, the valve closes to prevent regurgitation of blood from the left ventricle back into the left atrium 1
During diastole, the valve opens to allow blood flow from the left atrium into the left ventricle 1
The saddle shape of the annulus helps distribute mechanical stress across the valve components 1

Dysfunction of any component can lead to mitral valve disease, including primary (organic) mitral regurgitation and secondary (functional) mitral regurgitation 6, 5
Understanding the complex anatomy is essential for precise localization of pathology, planning surgical or transcatheter interventions, and predicting outcomes of repair techniques 1, 5
Carpentier's classification of leaflet motion helps understand mechanisms of mitral regurgitation, including Type I, Type II, and Type III leaflet motion 6
Left ventricular remodeling and tethering of the mitral valve play major roles in secondary mitral regurgitation 6, 5