Ventricular Septal Defect
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In the animation above, the oxygenated (red) blood in the left ventricle "shunts" through the VSD into the right ventricle and is pumped through the pulmonary artery to the lungs.
What Are Its Effects?

In a left to right shunt, blood that just returned from the lungs crosses the VSD and goes back to the lungs again. This causes increased pulmonary (lung) blood flow. A heart murmur occurs because there is a pressure difference between the two ventricles and there is turbulent blood flow crossing the hole. The smaller the hole, the louder the murmur. A medium to large VSD results in dilation of the left atrium and ventricle to accommodate the addition blood flow coming back from the lungs.

Ventricular Septal Defect (VSD) affects boys and girls with equal frequency. Children with VSD are affected differently depending on the size, location, and number of holes in the ventricular septum. Small holes generally cause little or no difficulty and often close naturally as the child grows.

Larger holes may interfere with a child's feeding and growth and may cause rapid breathing, irritability, excessive sweating, and poor weight gain. The vessels which carry blood from the heart to the lungs and back again may become congested, or overloaded, with blood, resulting in congestive heart failure (CHF). This usually occurs when the child is 6 to 8 weeks old.

With large VSDs, the lungs are receiving increased blood under higher than normal pressure. This can result in pulmonary hypertension (high blood pressure in the pulmonary artery). If this pressure becomes too high, the heart may be unable to function properly.