Ventricular Septal Defect Causes

No one knows what causes ventricular septal defects, but they probably come from a malformation of the heart that occurs while the infant is developing in the womb.

• There may be just one hole or several holes in the septum.
  
  
• The septum itself is divided into multiple areas, including the membranous part, the muscular part, and other areas called the inlet and outlet. Any or all of these parts can have a hole.
  
  
• The location of the hole depends on where the malformation takes place during fetal development.

The most common type of ventricular septal defect is the membranous variant. In this type, the hole is located below the aortic valve, which controls flow of blood from the left ventricle into the main artery of the body, the aorta.