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 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 between 0.1 percent to 0.4 percent of all live births and makes up about 20 percent to 30 percent of congenital heart lesions. Ventricular septal defects are probably one of the most common reasons for referral of an infant to a cardiologist.
Ventricular septal defects come in many locations and sizes. The ventricular septum is made up of different types of tissue, with one part composed of mainly muscle and another part made of thinner, fibrous tissue. The location and size of the hole within the septum will determine the consequences of the ventricular septal defect. Small ventricular septal defects rarely cause problems.
A physician usually discovers these holes by noticing a murmur on a routine physical exam. Most of these holes will close on their own, particularly if they are in the muscular portion of the septum. Even if these holes do not close, they will rarely cause any health problems. Rarely, these holes can be associated with other defects of the heart that with time can become important. Therefore, if the small ventricular septal defect does not close, the child should continue to be seen by a cardiologist for occasional checkups.
Large ventricular septal defects can cause problems, often in the first few months of life. Before birth, the pressure on the right side of the heart is equal to pressure on the left side of the heart. As soon as the baby takes its first breath, the pressure in the lungs and the right side of the heart starts to decrease. This process is slow and usually takes about 2-4 weeks for the pressure in the lungs to stabilize at the normal level of about 1/3 of the blood pressure in the aorta.
In the first 1 to 2 weeks of life, babies with large ventricular septal defects may do very well. But as the pressure in the right side of the heart decreases, blood will start to flow to the path of least resistance (i.e., from the left ventricle through the ventricular septal defect to the right ventricle and into the lungs). This will gradually lead to symptoms of congestive heart failure and must be treated.
Medium or moderate ventricular septal defects are more challenging to predict. Sometimes babies born with moderate ventricular septal defects will have problems with congestive heart failure like babies with large ventricular septal defects. Others will have no problems at all and just need to be watched.
Ventricular septal defects never get bigger and sometimes get smaller or close completely. This is why when a baby is diagnosed with a ventricular septal defect; most cardiologists will not recommend immediate surgery but will closely observe the baby and try to treat symptoms of congestive heart failure with medication to allow time to determine if the defect will close on its own.