Ventricular Septal Defects

A ventricular septal defect (VSD) is a congenital heart defect involving a hole in the wall between the ventricles, or pumping chambers, of the heart. About 42 in every 10,000 babies will have a ventricular septal defect.
The heart is a double-sided pump, and pressure on the two sides of the heart is different. To protect the lungs, pressure on the right side of the heart is quite low. But the left side is under much higher pressure because the left ventricle must eject blood to the body’s furthest reaches. It’s vital that the sides stay separate, otherwise the high pressure blood flow from the heart’s left side can damage the lungs. The heart’s valves help control blood flow through the heart, but the primary way the heart divides the two sides is through a wall called a septum.
In a normal infant, the wall between the chambers closes before the birth, so that oxygen-rich (or “red”) blood is kept from mixing with the oxygen-poor (or “blue”) blood. When the hole does not close, it may cause higher pressure in the heart or reduced oxygen to the body. To protect themselves from the higher pressure blood which escapes into the right ventricle, the delicate blood vessels in the lungs thicken. But because thickened vessels don’t allow blood to flow as well, the heart must work harder, generating more pressure.
Congenital VSDs are sometimes associated with other congenital conditions, such as Down Syndrome, but in many cases there is no known cause or inherited link. Signs of a ventricular septal defect might be present at birth or might not appear until well after birth; symptoms typically depend on the size of the defect.
Small VSDs sometimes close on their own or do not cause problems. Larger VSDs can eventually cause cyanosis (“blue baby syndrome”) and need to be corrected surgically. 

A VSD can occur anywhere along the ventricular septal wall, and different VSDs are named after their locations.

  1. Conoventricular Ventricular Septal Defect
    This is a hole where portions of the ventricular septum should meet just below the pulmonary and aortic valves.
  2. Perimembranous Ventricular Septal Defect
    This is a hole in the upper section of the ventricular septum.
  3. Inlet Ventricular Septal Defect
    This is a hole in the septum close to where the blood enters the ventricles through the tricuspid and mitral valves. This type of ventricular septal defect also might be part of another heart defect called an atrioventricular septal defect (AVSD).
  4. Muscular Ventricular Septal Defect
    This is a hole in the lower, muscular part of the ventricular septum and is the most common type of ventricular septal defect (occurring in approximately eighty percent of cases.)

Because of its location inside the heart and the length of time required to access it, a VSD could only be repaired with the use of a heart-lung machine. Accordingly, prior to the heart-lung machine becoming available, children with large VSDs often died in childhood, although some lived into their teens and beyond depending on the size of the defect. Today, children with VSDs which close on their own, with medication, or through surgical intervention typically live healthy lives of normal length.

Image of VSD, National Heart Lung and Blood Institute – Public Domain Image.

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