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Posterior leaflet of left atrioventricular valve

The posterior leaflet of the left atrioventricular valve, also called the posterior mitral leaflet, is one of the two cusps of the mitral (bicuspid) valve located between the left atrium and left ventricle. Compared to the anterior leaflet, it is shorter in height but longer in circumferential extent, occupying about two-thirds of the mitral annulus.

The posterior leaflet is attached to the posterior annulus of the mitral valve and is divided into three scallops (P1, P2, P3), separated by indentations. It is anchored to the papillary muscles via chordae tendineae, which ensure proper coaptation with the anterior leaflet during systole. This scalloped design provides flexibility and helps prevent regurgitation.

The posterior leaflet plays a central role in maintaining valve competence, unidirectional blood flow, and preventing mitral regurgitation. Abnormalities such as myxomatous degeneration, prolapse, flail scallops, or calcification are major contributors to mitral valve disease and surgical interventions.

Synonyms

  • Posterior mitral leaflet

  • Posterior leaflet of bicuspid valve

  • Posterior cusp of mitral valve

Function

  • Opens during diastole to allow ventricular filling from the left atrium

  • Coapts with the anterior leaflet during systole to prevent mitral regurgitation

  • Scalloped morphology (P1, P2, P3) allows flexible motion and effective closure

  • Provides stability for valve repair and surgical reconstruction

MRI Appearance

T1-weighted images:

  • Appears as a thin, low-signal structure attached to the posterior mitral annulus

  • More difficult to visualize than the anterior leaflet due to its smaller height

T2-weighted images:

  • Leaflet remains low signal relative to the hyperintense blood pool

  • Pathological thickening or edema within the leaflet shows intermediate to high signal

STIR (Short Tau Inversion Recovery):

  • Suppresses fat to better outline the leaflet against adjacent myocardium

  • Degenerative or inflammatory changes may appear hyperintense

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • Normal leaflet shows minimal enhancement

  • Abnormal enhancement suggests fibrosis, degeneration, or post-surgical changes

Cine MRI (Cardiac-Gated):

  • Cine T2: Provides excellent contrast between leaflet (dark) and blood pool (bright), allowing assessment of leaflet prolapse, flail scallop, regurgitant jets, and restricted motion

CT Appearance

Contrast-Enhanced CT (Cardiac CT / CCTA):

  • Posterior leaflet appears as a thin, scalloped structure within the mitral orifice

  • Multiphase imaging differentiates leaflet position in systole (closed) and diastole (open)

  • Calcification, prolapse, flail scallop, or thickening can be visualized

  • High-resolution CT is vital for preoperative mitral valve repair or replacement planning

CT images

Posterior leaflet of left atrioventricular valve MRI coronal image -img-00000-00000