Ventricular Septal Defect (VSD)

What is a ventricular septal defect?

Anatomy of the heart, normal

A ventricular septal defect is an opening in the ventricular septum, or dividing wall between the two lower chambers of the heart known as the right and left ventricles. VSD is a congenital (present at birth) heart defect. As the fetus is growing, something occurs to affect heart development during the first eight weeks of pregnancy, resulting in a VSD.

Normally, 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.

Anatomy of a heart with ventricular septal defect

What are the different types of VSD?

There are four basic types of VSD:

  • Membranous VSD. An opening in a particular area of the upper section of the ventricular septum (an area called the membranous septum), near the valves. This type of VSD is the most commonly operated on since most membranous VSDs do not usually close spontaneously.

  • Muscular VSD. An opening in the muscular portion of the lower section of the ventricular septum. This is the most common type of VSD. A large number of these muscular VSDs close spontaneously and do not require surgery.

  • Atrioventricular canal type VSD. A VSD associated with atrioventricular canal defect. The VSD is located underneath the tricuspid and mitral valves.

  • Conal septal VSD. The rarest of VSDs which occur in the ventricular septum just below the pulmonary valve.

Ventricular septal defects are the most commonly occurring type of congenital heart defect, accounting for about half of congenital heart disease cases.

Prevention & Risk Treatment

Prevention & Risk Treatment

What causes ventricular septal defect?

The heart is forming during the first eight 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.

Why is ventricular septal defect a concern?

If not treated, 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 right side of the heart. Extra blood then passes through the pulmonary artery into the lungs, causing higher pressure than normal in the blood vessels in the lungs.

A small opening in the ventricular septum allows a small amount of blood to pass through from the left ventricle to the right ventricle. A large opening allows more blood to pass through and mix with the normal blood flow in the right heart. Extra blood causes higher pressure in the blood vessels in the lungs. The larger the volume of blood that goes to the lungs, the higher the pressure.

The lungs are able to cope with this extra pressure for while, depending on exactly how high the pressure is. After a while, however, the blood vessels in the lungs 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 will diminish. This helps preserve the function of the lungs, 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 begins to occur, pressure in the right side of the heart will eventually exceed pressure in the left. In this instance, it will be 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.

Some ventricular septal defects are found in combination with other heart defects (such as in transposition of the great arteries).

What are the symptoms of a ventricular septal defect?

The size of the ventricular septal opening will affect the type of symptoms noted, the severity of symptoms, and the age at which they first occur. A VSD permits extra blood to pass from the left ventricle through to the right side of the heart, and the right ventricle and lungs become overworked as a result. 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. The following are the most common symptoms of VSD. However, each child may experience symptoms differently. Symptoms may include:

  • Fatigue
  • Sweating
  • Rapid breathing
  • Heavy breathing
  • Congested breathing
  • Disinterest in feeding, or tiring while feeding
  • Poor weight gain

The symptoms of VSD may resemble other medical conditions or heart problems. Always consult your child's doctor for a diagnosis.

Diagnosis

Diagnosis

How is a ventricular septal defect diagnosed?

Your child's doctor may have heard a heart murmur during a physical examination, and referred your child to a pediatric cardiologist for a diagnosis. A heart murmur is simply a noise caused by the turbulence of blood flowing through the opening from the left side of the heart to the right.

A pediatric cardiologist specializes in the diagnosis and medical management of congenital heart defects, as well as heart problems that may develop later in childhood. The cardiologist will perform a physical examination, listening to the heart and lungs, and make other observations that help in the diagnosis. The location within the chest where the murmur is heard best, as well as the loudness and quality of the murmur (such as, harsh or blowing) will give the cardiologist an initial idea of which heart problem your child may have. Diagnostic testing for congenital heart disease varies by the child's age, clinical condition, and institutional preferences. Some tests that may be recommended include the following:

  • Chest X-ray. A diagnostic test that uses X-ray beams to produce images of internal tissues, bones, and organs onto film. With a VSD, the heart may be enlarged because the right ventricle handles 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), and detects heart muscle stress.
  • Echocardiogram (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. A cardiac catheterization is an invasive procedure that 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 guided to the inside of the heart. Blood pressure and oxygen measurements are taken in the four chambers of the heart, as well as the pulmonary artery and aorta. Contrast dye is also injected to more clearly visualize the structures inside the heart.
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