Ventricular septal defect is a hole in the wall between the right and left ventricles of the heart. This abnormality usually develops before birth and is found most often in infants.
The ventricles are the 2 lower chambers of the heart. The wall between them is called the septum. A hole in the septum is called a septal defect.
If the hole is located between the upper chambers or atria, it is called an atrial septal defect.
Infants may be born with either or both types of defects. These conditions are commonly known as "holes in the heart."
Normally, unoxygenated blood from the body returns to upper chamber of the right side of the heart called the right atrium. It passes through the tricuspid valve into the right ventricle, which pumps the blood to the lungs to absorb oxygen. After leaving the lungs, the oxygenated blood returns to the left side of the heart, to the left atrium. It then passes through the mitral valve into the left ventricle, where it is pumped out to provide oxygen to all the tissues of the body.
A ventricular septal defect can allow newly oxygenated blood to flow from the left ventricle, where the pressures are higher, to the right ventricle, where the pressures are lower, and mix with unoxygenated blood. The mixed blood in the right ventricle flows back or recirculates into the lungs. This means that the right and left ventricles are working harder, pumping a greater volume of blood than they normally would.
Eventually, the left ventricle can work so hard that it starts to fail. It can no longer pump blood as well as it did previously. Blood returning to the left side of the heart from may back up into the lungs, causing pulmonary congestion, and blood returning the right side of the heart may further back up into the body, causing weight gain and fluid retention. Overall, this is called congestive heart failure.
If the VSD is large and surgically uncorrected, pressure can build excessively in the lungs, called pulmonary hypertension. The higher the lung or pulmonary pressure, the greater the chance of blood flowing from the right ventricle through the VSD to the left ventricle, causing unoxygenated blood to be pumped out to the body by the left ventricle, causing cyanosis (blue skin).
The risk for these problems depends on the size of the hole in the septum and how well the infant’s lungs function.