A ventricular septal defect (VSD) is a hole between the right and left pumping chambers of the heart.

The heart has four chambers: a right and left upper chamber called an atrium and a right and left lower chamber called a ventricle.

In the normal heart, the right and left chambers are completely separated from each other by a wall of muscle called a septum. The right atrium is separated from the left atrium by the atrial septum and the right ventricle is separated from the left ventricle by the ventricular septum.

It is normal for all infants to be born with a small hole between the two atria which usually closes within the first few weeks of life.

Normally there is no hole between the two ventricles, but some infants are born with these holes called ventricular septal defects.

Ventricular septal defects are among the most common congenital heart defects, occurring in 0.1 to 0.4 percent of all live births and making up about 20 to 30 percent of congenital heart lesions. Ventricular septal defects are probably one of the most common reasons for infants to see a cardiologist.