Posterior leaflet of left atrioventricular valve

The posterior leaflet of left atrioventricular valve (posterior cusp of mitral valve) is characterized by its broad circumferential attachment, occupying approximately two-thirds of the mitral annulus, and is typically quadrangular in shape.

It is divided into three scallops: P1 (lateral, adjacent to the anterolateral commissure), P2 (central, usually the largest and most variable in size), and P3 (medial, adjacent to the posteromedial commissure). These scallops are separated by indentations or clefts, which can vary in number and prominence, and accessory scallops or fused segments are common anatomical variants.

The posterior leaflet is generally narrower in radial length compared to the anterior leaflet, but the total leaflet area is roughly equivalent between the two. The hinge line of the posterior leaflet is inserted along the posterior mitral annulus, which is a thin, discontinuous fibrous structure interspersed with adipose tissue, and in some regions, the leaflet is directly attached to the ventricular and atrial myocardium, making this area more susceptible to annular dilation and calcification.

Chordal attachments to the posterior leaflet are complex: the anterolateral and posteromedial papillary muscles provide chordae to the lateral and medial halves, respectively. The posterior leaflet receives primary (free edge), secondary (body), and tertiary (base) chordae, with tertiary chordae sometimes attaching directly from the ventricular wall or trabeculations to the leaflet base or annulus.