Anatomy of left ventricular outflow tract.

The left ventricular outflow tract is here considered to be that region of the left ventricle that lies between the anterior cusp ofthe mitral valve and the ventricular septum. The ventricular septum lies at an angle of45 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 right face of the membranous septum gives attachment to the medial wall of the right atrium and also to a small part of the septal cusp of the tricuspid valve. The membranous septum is therefore partly atrioventricular. At its upper end the membranous septum is continuous with the right lateral wall of the root of the aorta. The root of the aorta passes to the right and upwards and the membranous septum separates the aorta from the right ventricle. 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.