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:
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.