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With the lung collapsed, pulmonary vascular resistance remains high during the fetal stage to prevent blood flow into the lungs. [2] As oxygenated blood arrives at the right atrium, the eustachian valve helps direct the oxygenated blood into the foramen ovale, an opening between the right and left atrium.
A pulmonary shunt is the passage of deoxygenated blood from the right side of the heart to the left without participation in gas exchange in the pulmonary capillaries. It is a pathological condition that results when the alveoli of parts of the lungs are perfused with blood as normal, but ventilation (the supply of air) fails to supply the perfused region.
Ductus arteriosus evolved with the lung in the ancestors of the lungfish as a connection between the pulmonary arteries and dorsal aorta. During embryonic development, reptiles, birds, and mammals all have either one or two paired ductus arteriosi that provide a fetal shunt of blood away from the lungs. [10]
This means that the heart is working against higher pressures, which makes it more difficult for the heart to pump blood. [1] In a fetus, there is high pulmonary vascular resistance (PVR) and low pulmonary blood flow as the fetus does not use the lungs for oxygen transfer, but instead relies on the placenta for oxygen. When the baby is born ...
An aortopulmonary shunt is created to connect the aorta to the main pulmonary artery to provide pulmonary blood flow to the lungs. The Glenn procedure disconnects the superior vena cava from the heart and connects it to the right pulmonary artery so deoxygenated blood from the upper body goes directly to the lungs.
Eisenmenger syndrome or Eisenmenger's syndrome is defined as the process in which a long-standing left-to-right cardiac shunt caused by a congenital heart defect (typically by a ventricular septal defect, atrial septal defect, or less commonly, patent ductus arteriosus) causes pulmonary hypertension [1] [2] and eventual reversal of the shunt into a cyanotic right-to-left shunt.
In the neonatal period, these patients depend on an aortopulmonary shunt that is maintained medically with prostaglandin and then surgically with an initial cardiac shunt procedure. As the patient will outgrow the shunt with time, they are evaluated for the Glenn bidirectional shunt when oxygen saturation begins to fall.
The Blalock–Thomas–Taussig shunt (BTT shunt), [1] previously known as the Blalock–Taussig Shunt (BT shunt), [2] is a surgical procedure used to increase blood flow to the lungs in some forms of congenital heart disease [3] such as pulmonary atresia and tetralogy of Fallot, which are common causes of blue baby syndrome. [3]