|
|
|
|
|
Eisenmenger's SyndromeEisenmenger's syndrome or Eisenmenger's reaction is defined as the process in which a left-to-right shunt in the heart causes increased flow through the pulmonary vasculature, causing pulmonary hypertension, which in turn, causes increased pressures in the right side of the heart and reversal of the shunt into a right-to-left shunt. Conditions needed for a person to be diagnosed with Eisenmenger's Syndrome are: 1. an underlying heart defect that allows blood to pass between the left and right sides of the heart. 2. pulmonary hypertension, or elevated blood pressure in the lungs 3. polycythemia, an increase in the number of red blood cells 4. the reversal of the shunt Etymology Eisenmenger's syndrome was so named by Dr. Paul Wood after Dr. Victor Eisenmenger, who first described the condition in 18971. Eisenmenger V. Die angeborenen Defekte der Kammerscheidewnde des Herzens. Zeitschr Klin Med 1897;32(Supplement):1-28. Etiology A number of congenital heart defects can cause Eisenmenger's syndrome, including atrial septal defects, ventricular septal defects, patent ductus arteriosus, and more complex types of acyanotic heart disease. Pathogenesis The left side of the heart is very muscular. It needs to be strong because it sends blood coursing through the body all the way to the tips of the fingers and toes. The right side of the heart is less muscular. It only needs to move the blood some inches, into the lungs. The lungs are a low pressure system, full of delicate capillaries embracing alveoli where the exchange of carbon dioxide from the blood for oxygen from the air takes place. When the left side of the heart pushes blood through the defect into the right heart, the right heart becomes stronger to deal with the extra volume. Over time, the increasing strength of the right side raises the blood pressure in the lungs creating pulmonary hypertension. The increased pressure causes delicate capillaries to die and be replaced with scar tissue. Scar tissue contributes nothing to oxygen transfer, but decreases the useful volume of the pulmonary vasculature. When you decrease the volume of a closed system, the pressure increases; with increased pressure, more capillaries die, so pulmonary hypertension in Eisenmenger's Syndrome tends to get worse, and the worse it gets, the faster it gets worse. The decrease in oxygen transfer reduces oxygen saturation in the blood, triggering high altitude adaptation as the body increases the production of red blood cells in an attempt to bring the oxygen saturations up. The large number of red blood cells is called polycythemia. Desperate for enough circulating oxygen, the body begins to dump immature red cells into the blood stream. Immature red cells are not as efficient at carrying oxygen as mature red cells, and they are less flexible, less able to easily squeeze through tiny capillaries in the lungs, and so contribute to death of pulmonary capillary beds. A person with Eisenmenger's Syndrome is paradoxically subject to the possibility of both uncontrolled bleeding and random clots. The large number of red cells tends to overpower the platelets. The rough places in the heart lining at the site of the septal defects/shunts tend to gather platelets and keep them out of circulation, and may be the source of random clots. Random clots are more immediately dangerous, so some blood thinning medication like warfarin is administered. Free communication of the blood between the left and right sides of the heart means that the person can be viewed as having a one chambered heart, where the blood leaves through the channel of least resistance. When such a person is exerting themselves, the resistance is less through the aorta to the body, so unoxygenated blood is circulated, dropping the oxygen saturation even more. References - Wood, P. Pulmonary hypertension with special reference to the vasoconstrictive factor. Br Heart J 1958;20:557-570.
|
 |
|
| Copyright 2005-2009 OnPedia.com. All Rights Reserved |
|
|