Ventricular Septal Defect



A ventricular septal defect (VSD) is a hole in the wall that separates the heart’s lower pumping chambers (left and right ventricles). The hole provides an opening for blood to cross the wall (septum), from the left side to the right side of the heart. When this occurs, some of the blood in the left ventricle, which has just come back to the heart from picking up oxygen in the lungs, may go into the right ventricle and immediately back to the lungs.

An illustration showing the presentation of ventricular septal defect.

These holes can exist in various parts of the wall between the bottom pumping chambers of the heart. They can occur:

  • Near the valves that let blood into the pumping chambers (inlet)
  • In the thick section of the septum (muscular)
  • In the thinner fibrous area of the wall (perimembranous)
  • Toward the main vessel leaving the heart (outlet)
  • High up toward the valve that lets blood out to the lungs (supracristal)

An increase in blood flow across the hole to the lungs can cause the lungs to become congested. Congestion of the lungs interferes with their job of transferring oxygen from the air to the blood and carbon dioxide (CO2) from blood to air. The extra blood returning from the lungs to the left heart chambers can cause them to enlarge. When the heart is overburdened and the lungs become congested, a condition called congestive heart failure occurs.

Because the heart and lungs have to work harder, a baby with a VSD will become short of breath, particularly with the exertion of feeding (which is the most exercise a baby does). This could lead to poor feeding and eventually to poor weight gain and growth.

According to the Centers for Disease Control and Prevention (CDC), VSD is the most common type of congenital heart defect, occurring in about 1 in every 240 babies born in the U.S. each year.1


If the VSD is small, the amount of increased blood flow into the lungs won’t significantly increase, and the child won’t be noticeably affected. If it’s larger and allows much more blood than normal to flow to the lungs, serious problems may result, including:

  • Fatigue of the heart – The heart has to work harder to deal with the inefficient circulation of blood.
  • Congestion of the lungs – Lung congestion leads to difficulty in breathing.
  • Poor weight gain – An inability to tolerate the exertion needed to feed properly causes a lack of proper weight gain in babies with VSD.
  • Decreased oxygen to the body – If excessive damage has occurred to the lungs, this leads to a difficulty in getting blood to pass through the lungs. In this case, the flow across the VSD may actually reverse, causing blue blood to go directly to the body, a condition called Eisenmenger syndrome.

Progression and complications

Some VSDs may spontaneously close without treatment, but the larger the defect, the less likely it will. The location of the VSD also influences whether it closes on its own, with defects in the thicker muscular part of the septum being the most likely to close over time.

If a moderate or large VSD is left untreated, the result may be irreversible damage to the blood vessels of the lungs. It can even cause blood flow to reverse so that poorly oxygenated (blue) blood goes directly to the body (Eisenmenger syndrome). Patients with Eisenmenger syndrome are more likely to suffer from strokes and brain infections. If the damage progresses, death can result, typically in the fourth or fifth decade of life.

Baby and stethoscope

Children's Heart Health

Information for parents of children with pediatric heart conditions. Read more about conditions, tests, and treatments for congenital heart disease.

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Claire Kurz

The Kurz family never gave up hope for their baby girl and brought her home at six days old to meet her big sister Madeline. For the next five weeks, they tried to maintain a sense of normalcy while they waited to get the call from a surgeon who might be able to save Claire’s life.

Claire Kurz