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Anterior leaflet of left atrioventricular valve

The anterior leaflet of the left atrioventricular valve, also called the anterior mitral leaflet, is one of the two leaflets of the mitral (bicuspid) valve, positioned between the left atrium and left ventricle. It is larger, more triangular, and thicker than the posterior leaflet, occupying about one-third of the mitral annular circumference.

It attaches to the anterior mitral annulus, forming the aortomitral continuity adjacent to the aortic root. It extends into the left ventricular cavity and is anchored by chordae tendineae from the papillary muscles. During diastole, it opens widely to allow blood flow into the left ventricle, and during systole, it coapts with the posterior leaflet to prevent backflow into the left atrium.

The anterior mitral leaflet is central to maintaining unidirectional blood flow, efficient ventricular filling, and prevention of mitral regurgitation. Abnormalities such as prolapse, calcification, thickening, or flail leaflet are major causes of valvular heart disease.

Synonyms

  • Anterior mitral leaflet

  • Anterior leaflet of bicuspid valve

  • Aortomitral leaflet

Function

  • Opens during diastole to permit atrial-to-ventricular filling

  • Closes during systole to prevent regurgitation into the left atrium

  • Works with posterior leaflet, chordae tendineae, annulus, and papillary muscles to maintain valve competence

  • Provides part of the aortomitral curtain linking atrium, ventricle, and aorta

MRI Appearance

T1-weighted images:

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

  • Better assessed in cine imaging due to motion

T2-weighted images:

  • Leaflet remains low signal relative to hyperintense blood pool

  • Pathological thickening or edema appears hyperintense

STIR (Short Tau Inversion Recovery):

  • Suppresses fat signal, improving leaflet visualization

  • Pathology such as myxomatous degeneration or inflammatory infiltration may show increased signal

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • Normal leaflet shows minimal enhancement

  • Abnormal enhancement indicates fibrosis, inflammation, or post-surgical changes

Cine MRI (Cardiac-Gated):

  • Cine T2: Provides high contrast between the low-signal leaflet and hyperintense blood pool, enabling clear visualization of leaflet motion, regurgitant jets, and dynamic coaptation with the posterior leaflet

CT Appearance

Contrast-Enhanced CT (Cardiac CT / CCTA):

  • Leaflet appears as a thin, mobile structure within the mitral orifice

  • Contrast-enhanced blood pool delineates leaflet position in systole vs diastole

  • Excellent for assessing calcification, thickening, restricted mobility, and preoperative repair planning

  • High-resolution, multiplanar reconstructions show the aortomitral curtain and leaflet morphology

CT image

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