Basics of Ventricular Septal Defect (VSD)
A ventricular septal defect (VSD) is a hole in the part of the dividing wall (or “septum”) that separates the ventricles, the lower chambers of the heart. VSD is a congenital (present at birth) heart defect. As the fetus grows, something occurs to affect heart development during the first eight weeks of pregnancy, resulting in a VSD.
In a normal heart, oxygen-poor (blue) blood returns to the right atrium from the body, travels to the right ventricle, then is pumped into the lungs, where it receives oxygen. Oxygen-rich (red) blood returns to the left atrium from the lungs, passes into the left ventricle, and then is pumped out to the body through the aorta.
A ventricular septal defect allows oxygen-rich (red) blood to pass from the left ventricle, through the opening in the septum, and then mix with oxygen-poor (blue) blood in the right ventricle.
There are four basic types of VSD:
- Muscular VSD. The most common type of VSD, it is an opening in the muscular portion of the lower section of the ventricular septum. A large number of these close spontaneously and do not require surgery.
- Perimembranous VSD. This opening is in an area of the upper section of the ventricular septum called the membranous septum, located near the valves. This type of VSD is the one that is most commonly treated by surgery because most do not close on their own.
- Atrioventricular canal type VSD. This VSD is associated with atrioventricular canal defect. The VSD is located underneath the tricuspid and mitral valves.
- Conal septal VSD. The rarest of VSDs, it occurs in the ventricular septum just below the pulmonary valve.
Fast Fact of Ventricular Septal Defect
- Ventricular septal defects are the most common type of congenital heart defects and account for 25 percent of congenital heart disease.
Causes of Ventricular Septal Defect
The heart forms during the first eight weeks of pregnancy. It begins as a hollow tube that later partitions into two sides, separated by septa (or walls). Ventricular septal defects occur when the partitioning process does not complete, leaving an opening in the ventricular septum.
Some congenital heart defects may have a genetic link, either occurring due to a gene defect, 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 cause.
Symptoms of Ventricular Septal Defect
The size of the ventricular septal opening affects the type and severity of symptoms as well as the age they first occur. A VSD permits extra blood to pass from the left ventricle through to the heart’s right side, a condition that overworks the right ventricle and lungs. The larger the opening, the greater the amount of blood that passes through and overloads the right ventricle and lungs.
Symptoms often occur in infancy and can vary depending on the child. Common symptoms include:
- Rapid breathing
- Heavy breathing
- Congested breathing
- Disinterest in feeding, or tiring while feeding
- Poor weight gain
Because symptoms of VSD may resemble other medical conditions or heart problems, it is important to consult a child's physician for a diagnosis.
Health problems associated with Ventricular Septal Defect
If left untreated, this heart defect can cause lung disease. When blood passes through the VSD from the left ventricle to the right ventricle, a larger volume of blood than normal must be handled by the heart’s right side. Extra blood then passes through the pulmonary artery into the lungs, causing higher than normal pressure in the lungs’ blood vessels.
A small opening in the ventricular septum allows a small amount of blood to pass from the left ventricle to the right ventricle. A large opening allows more blood to pass through and mix with normal blood flow in the right heart. Extra blood causes higher pressure in the lungs’ blood vessels. The larger the volume of blood that goes to the lungs, the higher the pressure.
The lungs can cope with this extra pressure for a while, but eventually the lungs’ blood vessels become diseased by the extra pressure.
As pressure builds up in the lungs, the flow of blood from the left ventricle, through the VSD, into the right ventricle, and on to the lungs diminishes. This helps preserve the lungs’ function, but causes yet another problem. Blood flow within the heart goes from areas where the pressure is high to areas where the pressure is low. If a ventricular septal defect is not repaired, and lung disease occurs, pressure in the right side of the heart eventually exceeds pressure in the left. In this case, it is easier for oxygen-poor (blue) blood to flow from the right ventricle, through the VSD, into the left ventricle, and on to the body. When this happens, the body does not receive enough oxygen in the bloodstream to meet its needs.
Because blood is pumped at high pressure by the left ventricle through the VSD, tissue damage may eventually occur in the right ventricle. Bacteria in the bloodstream can easily infect this injured area, causing a serious illness known as bacterial endocarditis.
Some ventricular septal defects are found in combination with other heart defects, such as in transposition of the great arteries.
Tests, procedures and diagnosis of Ventricular Septal Defect
A child's physician may hear a heart murmur during a physical examination and referred the child to a pediatric cardiologist, who specializes in the diagnosis and treatment of congenital heart defects and heart problems that may develop later in childhood. The cardiologist performs a physical examination, listens to the child’s heart and lungs and makes other observations. Heart murmurs are evaluated on the basis of pitch, loudness and duration, which give the cardiologist an initial idea of which heart problem a child may have. Diagnostic testing for congenital heart disease varies by a child's age and clinical condition and may include:
- Chest X-ray. This diagnostic test uses X-ray beams to produce images onto film of internal tissues, bones and organs. With a VSD, the heart may be enlarged due to the right ventricle handling larger amounts of blood flow than normal. Also, there may be changes that take place in the lungs due to extra blood flow that can be seen on an X-ray.
- Electrocardiogram (ECG or EKG). A test that records the electrical activity of the heart, shows abnormal rhythms (arrhythmias or dysrhythmias) and detects heart muscle stress.
- Echocardiogram (or “echo”). A procedure that evaluates the structure and function of the heart by using sound waves recorded on an electronic sensor that produce a moving picture of the heart and heart valves. An echo can show the pattern of blood flow through the septal opening, and determine how large the opening is, as well as much blood is passing through it.
- Cardiac catheterization. This invasive procedure gives very detailed information about the structures inside the heart. Under sedation, a small, thin, flexible tube (catheter) is inserted into a blood vessel in the groin, and then guided to the inside of the heart. Blood pressure and oxygen measurements are taken in the four chambers of the heart, pulmonary artery and aorta. In addition, contrast dye is injected to more clearly visualize the structures inside the heart.
Treatment for Ventricular Septal Defect
A child’s physician determines the specific treatment for VSD based on:
- A child's age, overall health and medical history
- Severity of the disease
- A child's tolerance for specific medications, procedures or therapies
- Expectations for the course of the disease
- Parents’ opinions or preferences
Small ventricular septal defects may close spontaneously as a child grows. A larger VSD usually requires surgical repair. Regardless of the type, once a ventricular septal defect is diagnosed, a child's cardiologist evaluates the child periodically to see if it is closing on its own. A VSD is repaired if it has not closed on its own to prevent lung problems that develop from long-term exposure to extra blood flow. Treatment may include:
- Medications. Some children have no symptoms and require no medication. However, most children may need to take medications to help the heart work better, due to the strain placed on the heart’s right side from the extra blood passing through the VSD. Medications that may be prescribed include:
- Digoxin. A medication that helps strengthen the heart muscle, enabling it to pump more efficiently.
- Diuretics. The body's water balance can be affected when the heart is not functioning well. These medications help the kidneys remove excess fluid from the body.
- ACE inhibitors. Medications that lower the blood pressure in the body, making it easier for blood to be pumped from the left ventricle into the body.
- Adequate nutrition. Infants with a larger VSD may become tired when feeding, and are not able to eat enough to gain weight. Options that ensure a baby has adequate nutrition include:
- High-calorie formula or breast milk. Special nutritional supplements may be added to formula or pumped breast milk that increase the number of calories per ounce, thus allowing a baby to drink less and still consume enough calories to grow properly.
- Supplemental tube feedings. Feedings given through a small, flexible tube that passes through the nose, down the esophagus, and into the stomach, can either supplement or replace bottle feedings. Infants who can drink only a part of their bottle may be fed the remainder through a feeding tube. Infants who are too tired to bottle feed may receive their formula or breast milk through a feeding tube alone.
- Infection control. Children with certain heart defects are at risk for developing an infection of the inner surfaces of the heart known as bacterial endocarditis. It is important for parents to inform all medical personnel that their child has a VSD so it can be determined if antibiotics are necessary before a procedure.
- Surgical repair. The goal is to repair the septal opening before the lungs become diseased from excess blood flow and pressure. Repair is indicated for defects causing symptoms, such as poor weight gain and rapid breathing. A child's cardiologist recommends when the repair should be performed based on echocardiogram and cardiac catheterization results. The operation is performed under general anesthesia. Depending on the size of the heart defect and a physician's recommendations, the ventricular septal defect will be closed with stitches or a special patch.
- Interventional cardiac catheterization. A child's VSD may be repaired by a cardiac catheterization procedure. One technique uses a device called a septal occluder. During this procedure, the child is sedated and a small, thin flexible tube is inserted into a blood vessel in the groin and guided into the heart. Once the catheter is in the heart, the cardiologist passes the septal occluder into the VSD. The septal occluder closes the ventricular septal defect, providing a permanent seal.