Development of ventricular septum

Interventricular septum has two components, Trabecular and membranous part of septum

Trabecular septum	Membranous septum
Develop from primitive interventricular septum	Develop from Proximal bulbar septum and proliferation from AV cushion

Embryology of ventricular septum and correlation with type of VSD.

There are three important types of VSD.

1. Inlet type of VSD
2. Outlet type of VSD
3. Trabecular type.

Inlet type of VSD is due to the malalignment between the inlet and trabecular septum.

Here the defect in ventricular septum originate from the AV cushions.

Outlet type of VSD : Occur due to malalignment between the outlet and trabecular septum.

The defect is derived from proximal bulbar septum.

Trabecular type of VSD : Defect occur in that part of septum derived from primitive ventricular septum.

Types of VSD are

Perimembranous

It is the most common defect also called as subaortic or infracristal

Inlet type

Subtricuspid / AV canal type

Outlet type

Subpulmonic supra critical or infundibulbar

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