Eisenmenger's Syndrome

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People who have Eisenmenger's syndrome are usually born with a large hole in the heart. The most common situation in which this occurs is when there is a hole (defect) between the two pumping chambers (ventricles), called a ventricular septal defect (VSD).

This hole permits blood to flow from the high-pressure (red, oxygen carrying) left-sided circulation to the lower-pressure (blue, oxygen poor) right-sided circulation. This abnormal blood flow is called a left-to-right shunt and follows this path because the left ventricle usually has a much higher pressure than the right ventricle.

A left-to-right shunt allows an increased volume of blood into the pulmonary circulation. The increased volume or flow to the lung (pulmonary) arteries causes the pressure in the pulmonary circulation to rise. This elevated pressure in the lungs is called pulmonary hypertension.

Pulmonary hypertension over time may damage the delicate pulmonary blood vessels. As this lung vessel damage continues, the pressure in the pulmonary arteries will progressively rise. The walls of the pulmonary vessels become thick-walled and stiff and some vessels may actually become blocked. This is an irreversible situation called Pulmonary Vascular Disease (PVD).

See Treatment of Pulmonary hypertension.

These damaged pulmonary vessels can have such a high resistance to blood flow that the pressure in the right ventricle becomes elevated as it struggles to pump blood forward into the lungs. The right ventricle normally would have a pressure of about 25 mmHg. In pulmonary hypertension, the right ventricular pressure can become 100 mmHg or more. The right ventricular pressure may increase enough to equal or exceed the left ventricular pressure. When this happens, right-to-left or reversed shunting of blood will occur. The blue (low oxygen) blood in the right side (venous) circulation is pushed back into the red (oxygenated) left side (arterial) circulation, bypassing the lungs. This is what causes a person with Eisenmenger's syndrome to have a blue tinge to the skin or cyanosis.

The pulmonary hypertension together with right-to-left shunting of blood is known as Eisenmenger's syndrome.

The syndrome can develop with different types of congenital heart defects. The most common is with a ventricular septal defect but it may also occur with a patent ductus arteriosus (PDA).

A PDA is a persistent connection between the aorta and pulmonary artery. This connection would normally close shortly after birth. Eisenmenger's syndrome in rare instances may also develop with an atrial septal defect. The syndrome may also occur in complex cyanotic heart defects such as a heart with one ventricle.