Diagram shows four types of ventricular septal defect (VSD). The relationship
between the outlet septum (green) and septomarginal trabecula (SMT) defines
the location of the VSD. (A) The outlet septum attaches to the
anterior limb of the septal band, resulting in a subaortic VSD.
(B) The outlet septum attaches to the posterior limb of the
septal band, resulting in a subpulmonic VSD. (C) In the doubly
committed VSD, the outlet septum is absent. (D) A remote VSD is
not related to the outlet septum, and the distance between the VSD and
semilunar valve is greater than the size of the aortic valve. Ao = aorta, LV
= left ventricle, PA = pulmonary artery, RV = right ventricle.