Eisenmenger syndrome is a condition that results from abnormal blood circulation caused by a defect in the heart. Most often, people with this condition are born with a hole between the two pumping chambers -- the left and right ventricles -- of the heart (ventricular septal defect). The hole allows blood that has already picked up oxygen from the lungs to flow back into the lungs, instead of going out to the rest of the body.
Other heart defects that can lead to Eisenmenger syndrome include:
Over time, typically over many years, increased blood flow can damage the small blood vessels in the lungs. This causes high blood pressure in the lungs. As a result, the blood backs up and does not go to the lungs to pick up oxygen. Instead, the blood goes from the right side to the left side of the heart, allowing oxygen-poor blood to travel to the rest of the body.
Eisenmenger syndrome may begin to develop before a child reaches puberty. However, it also can develop in young adulthood, and may progress throughout young adulthood.