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Ventricular septal defect, or VSD, refers to an OPENING in the interventricular septum that separates the two ventricles of the heart.
In normal circulation, oxygen-poor blood from the body returns to the RIGHT side of the heart where it is pumped into the pulmonary artery and to the lungs. After being oxygenated, oxygen-rich blood from the lungs returns to the LEFT side of the heart to be pumped into the aorta and out to the body.
Pathology: A VSD allows abnormal blood flow between the two ventricles. The NET flow of blood, called a SHUNT, is usually from LEFT to RIGHT due to significantly HIGHER blood pressure in the LEFT side of the heart. This is because the left side has to pump blood all over the body while the right side only needs to send it to the lungs. If the defect is small, the shunt is negligible and does not result in any symptoms. A large defect, on the other hand, may OVERLOAD the right side of the heart, causing it to FAIL. Heart failure symptoms usually appear during the first few weeks of life and include: fatigue, shortness of breath, difficulty feeding and poor growth.
Without treatment, other complications may also occur. As the right ventricle continuously pumps MORE blood to the lungs, the entire pulmonary vasculature may be overloaded and pulmonary Hypertension may result. To OVERCOME the high pressure in the lungs, the right ventricle has to generate even HIGHER pressure, which eventually becomes GREATER than that of the LEFT ventricle. This REVERSES the direction of the shunt, causing oxygen-POOR blood to flow from RIGHT to LEFT and be sent to all tissues of the body. The resulting oxygen DEPRIVATION may be seen as a BLUISH skin color, known as CYANOSIS.
A VSD can happen alone or in combination with other congenital defects in conditions such as Down syndrome, or tetralogy of Fallot. The cause is unknown but likely to involve both genetic and environmental factors.
The turbulence of abnormal blood flow in VSD produces heart murmurs, which can be heard using a stethoscope. Diagnosis is confirmed by echocardiography.
VSD is the most common congenital heart defect in infants, but the defect is small in most cases. Small defects usually close on their own in early childhood and no treatment is needed. Large defects that produce symptoms usually require surgical closure in the first year of life.
