Aortic vestibule

The portion of the ventricle immediately below the aortic orifice is termed the aortic vestibule, and possesses fibrous instead of muscular walls.

In daily routine, the aortic vestibule is termed as left ventricular outflow tract (LVOT).The LVOT is widely studied and described in cardiology imaging for TAVI measurements and because of the left ventricular outflow tract obstruction (LVOTO):

• The left ventricular outflow tract (LVOT) is the region of the left ventricle that lies between the anterior cusp of the mitral valve and the ventricular septum. 
• As the ventricular septum lies at an angle of 45 degrees to the median plane, the “anterior” wall of the outflow tract is therefore anteromedial and the “posterior” wall is posterolateral.
• In the anterior wall are both the muscular and membranous parts of the ventricular septum. The outflow septal myocardium is smooth-walled. At the junction of the muscular and membranous parts of the septum lies the atrioventricular bundle.
• The posterior wall of the outflow tract is formed not only by the anterior mitral cusp but also by the 'intervalvar septum' and, in its upper part, by a curtain formed by the fusion of the anterior and posterior mitral cusps.
• There is no line of demarcation on its anterior (septal) wall to indicate the lower border of the tract. This is indicated on its posterior wall by the free lower border of the anterior cusp of the mitral valve.