What causes ventricular septal defect?
The heart is forming during the first 8 weeks of fetal development. It begins as a hollow tube, then partitions within the tube develop that eventually become the septa (or walls) dividing the right side of the heart from the left. Ventricular septal defects occur when the partitioning process does not occur completely, leaving an opening in the ventricular septum.
Some congenital heart defects may have a genetic link, either occurring due to a defect in a gene, a chromosome abnormality, or environmental exposure, causing heart problems to occur more often in certain families. Most ventricular septal defects occur sporadically (by chance), with no clear reason for their development.
The septum is the wall that separates the right and left sides of the heart. A hole in the wall between the two lower chambers is called a ventricular septal defect, or VSD for short. Normally, blood entering the right side of the heart stays on the right side (this is low oxygen blood), and blood on the left side of the heart stays on the left side (this is oxygen rich blood) which is then pumped to the rest of the body. When a defect or "hole" is present between the ventricles (or lower chambers), blood from the left side of the heart is forced through the defect to the right side every time the heart beats. It then goes back to the lungs even though it is already rich in oxygen. Because of this, blood that is not yet oxygen rich can’t get to the lungs.