What is Eisenmenger syndrome?

What is Eisenmenger syndrome?

Eisenmenger syndrome is a late complication of certain birth defects of the heart. Fortunately it is rare now-a-days because most conditions which can cause Eisenmenger syndrome later, are detected by screening of babies soon after birth and treated early so that this complication does not develop later. It is a condition with high pressure in the blood vessels of the lungs and bluish discoloration of body due to reduced oxygen saturation in blood.

When there is a defect in the walls between the chambers blood flows from the left sided chamber to the right sided chamber with lower pressure. Similar situation occurs when there is persistent communication between the aorta and pulmonary artery also. Aorta is the largest blood vessel carrying oxygenated blood to the whole body. Pulmonary artery is the blood vessel carrying blood returning from the body after oxygen extraction, to the lungs for oxygenation. A communication between the two is known as patent ductus arteriosus or PDA. In patent ductus arteriosus, blood flows from the aorta at high pressure to the pulmonary artery at lower pressure.

Similar situation is there when there is a defect in the wall between the upper chambers of the heart known as atrial septal defect (ASD). Blood flows from the left atrium to the right atrium. Left atrium is the left upper chamber which receives oxygenated blood from the lungs. Right atrium is the right upper chamber which receives blood returning from the body after oxygen extraction.

When there is defect in the wall between the lower chambers known as ventricular septal defect (VSD), blood flows from the left ventricle to the right ventricle. Ventricles are the lower chambers of the heart which receives blood from the corresponding atrial chambers. All these three leaks are called left to right shunts in general and cause increased blood flow to the lungs. When the blood flow to the lungs increase, the pressure in the lungs rise.

For a variable period of time depending on the size of the leak and some other factors, the lung accommodates the extra blood flow by enlarging its blood vessels. But after some time this mechanism fails and the blood pressure in the lungs rise disproportionately. When the pressure in the pulmonary artery rises above that in the aorta, the shunt across the patent ductus arteriosus or PDA, reverses so that blood flows from pulmonary artery to aorta.

Similarly, when the right ventricular pressure rises above that in left ventricle, the flow across the ventricular septal defect reverses. Blood flows from right ventricle to the left ventricle. Similar reversal can also occur across the atrial septal defect (ASD) so that blood flows from right atrium to left atrium. It is this situation of flow reversal due to high pulmonary artery pressures, which is called Eisenmenger syndrome. By the time it occurs, severe damage would have occurred in the blood vessels of the lungs due to longstanding high pressure. The rapidity with which this complication occurs depends on the size of the birth defect as well as some other factors.

When the shunting of the blood in any of the three defects becomes right to left instead of left to right, blood returning from the body after oxygen extraction gets partly pumped back to the body. This reduces oxygen levels in the blood vessels of the body. Body tries to compensate by increasing red blood cell content of the blood instead. Though this allows blood to carry more oxygen, it leads to increased viscosity of blood. The thicker blood starts obstructing the flow in the small blood vessels.

Blood viscosity can be reduced by blood letting, but it may start a vicious cycle as body starts to produce more red blood cells to compensate. So it is clear that Eisenmenger syndrome is better prevented than treated, like any other disease. Early detection of birth defects and repair when feasible, is the way to prevent Eisenmenger syndrome. All birth defects may not need surgical repair. Many can be repaired by non-surgical methods by implanting a device introduced through the blood vessel. An ultrasound study of the heart known as echocardiogram is useful both in detecting these defects and assessing suitability for procedures.

Small defects may not increase pressure in the lungs and are left alone, except in the case of a patent ductus arteriosus. In case of patent ductus arteriosus, even small defects will be closed as the procedural risk is low. Small defects have a risk of infection at some point in life. But procedure risk being higher than this risk, small defects in the walls between heart chambers are left alone. They will be observed regularly with prompt treatment for infections in other parts of the body.

Once Eisenmenger syndrome has developed, potential rare complications like stroke, infections of brain, bleeding from the lungs and increase in uric acid levels of blood are watched for. Most children who had heart failure due to large defects will get relief when Eisenmenger syndrome develops as the blood flow to the lungs comes down. This may be mistaken for spontaneous decrease in size of the defect. An echocardiogram done in suspected situations can very well tell whether it is improvement due to spontaneous decrease in size of the defect or development of Eisenmenger syndrome. Many persons with Eisenmenger syndrome go on for a long time with mild symptoms. In the unfortunate few who are really disabled, heart lung transplantation is a final option.