Eisenmingers Syndrome

Eisenmenger Syndrome
It is highly advisable to read my posts on morphology in order to understand why these defects develop embryologically.

This is a defect that occurs when a shunt changes from left to right, to right to left. The definition excludes defects such as common atrium, single ventricle, anomalous veins and a truncus arteriosis.

The reason for this is that these congenital defects obligate mixing of systemic and pulmonary flow whereas Eisenmenger implies a long term shunt that has damaged the lungs to the point that surgery cannot be done to correct the malformation.

For instance, a VSD (ventricular septal defect), ASD (atrial septal defect) or an arterial defect (such as D-transposition) that has persisted for many years may damage the pulmonary vascular bed to a point that shunt reversal may occur.

Undetected shunts may persist well into adulthood. Large volumes of blood are delivered from the left side to the right side of the heart via these types of shunts, and any pressure problems will aggravate the situation.

Large shunts may go undiagnosed due to the fact that it may not present a murmur, and may only be detected later in life once irreparable damage has been done to the lungs. This continuous pressure and volume overload may eventually equalize pressures between the right and left sides of the heart until a reversal of blood flow occurs.

Remember, in the neonate, normal heart pressure is 1/3 on the right as it is on the left. The right side of the heart delivers blood flow into the lungs, and the pressure is about 25 mmHg. Left sided pressures are approximately 75 mmHg.

This pressure difference is what keeps blood moving in one direction throughout the circulatory system (flow occurs from a high pressure environment to a low pressure environment). If pressures equalize, then flow tends to stop and cyanosis occurs.

Lungs exist in a low pressure environment. If they are exposed to constant increases in pressure and volume, then an aggressive form of pulmonary vascular resistance will manifest, and eventually lead to right sided failure. Undetected shunts will eventually result in this right sided collapse, and hence Eisenmenger syndrome.

Eisenmenger syndrome may also be called “end stage pulmonary hypertension”. Once these patients no longer respond to palliative procedures (such as pharmacological therapy), they may become candidates for heart-lung transplants.

Pulmonary banding may also be used. It is a procedure that alleviates pulmonary overcirculation by suturing an adjustable band across the pulmonary artery trunk. Sutures are tightened until pressures distal to the are within ideal levels.

Prior to transplantation, drug therapy seems to be the best approach. The drugs of choice are vasodilators and vasoconstrictive blockers that prevent damage to the lungs while preserving function.