Septal cusp

The septal cusp of the left atrioventricular valve arise from the septal margin of the left atrioventricular orifice and is cranioventrally located.

The septal cusp (anterior mitral leaflet) is cranial, contiguous with the caudal aspect of the aortic root, and extends more fully into the lumen of the LV chamber when compared to the posterior leaflet. This mitral-aortic fibrous continuity is an important anatomic feature of cardiac anatomy and is especially useful during echocardiography. The anterior leaflet functionally separates the LV inflow and outflow tracts, with the former confined by the mitral valve orifice and the latter formed by the anterior leaflet, ventricular septum, aortic valve orifice, and proximal aorta.

Note that the two mitral leaflets (cusps of left atrioventricular valve) are identified by an inconsistent nomenclature:

• The septal cusp is also called the anterior, cranial, or septal leaflet.

• The parietal cusp, the leaflet closer to the LV free wall, and positioned more caudodorsally, is called the posterior, caudal, parietal, or mural leaflet.

• Regardless of veterinary nomenclature, clinicians (especially echocardiographers) most often use the human terminology of “anterior” and “posterior” for these mitral components.