'At birth, the following changes must occur in that the gaseous exchange must now occur in the lungs of the infant after switching off the placental circulation by cutting the umbilical cord and closing heart shunts of the fetus'
Fetal and Newborn Cardiovascular System
The fetal circulatory system works differently during pregnancy than at the birth of a child. During pregnancy, the placenta is connected by the umbilical cord to the fetus, where the placenta is an organ that implants to the mother’s uterus during pregnancy. The umbilical cord has blood vessels that supply the fetus with nutrients, oxygen, and aids the fetus to receive life support from the mother via the placenta. Carbon dioxide and other waste products are sent back from the fetus through the same umbilical cord, via the placenta into the circulation system of the mother and then eliminated (Artman, Mahony & Teitel, 2017).
The circulatory system of the fetus has two right to left shunts which are mini-passages used to direct the blood which requires oxygen. These shunts serve as ways in which they can bypass body parts which have not yet developed while the fetus is still in the womb (Artman, Mahony & Teitel, 2017). Shunting of the blood can only be in a left-right shunt that is systemic circulation to pulmonary circulation, where blood with oxygen flows in the left to the right shunt. The pulmonary to systemic circulation (right-left shunt) is where the deoxygenated blood flows from the pulmonary circulation directly to the systemic circulation (Artman, Mahony & Teitel, 2017).
At birth, the following changes must occur in that the gaseous exchange must now occur in the lungs of the infant after switching off the placental circulation by cutting the umbilical cord and closing heart shunts of the fetus (Artman, Mahony & Teitel, 2017). After birth, the umbilical cord clamps together and the baby doe does not receive life support from the mother, and as the baby takes the first breath, its lungs begin to expand while the fluid in the lungs is cleared. The reduction of pulmonary pressure and increase in blood pressure of the baby results in a reduced need to shunt blood by the ductus arteriosus. The changes then result in the left atrium of the baby’s heart to increase while the pressure in the right atrium is decreased. This pressure shift resultsin the foramen ovales to close (Artman, Mahony & Teitel, 2017). This closure of foramen ovales and ductus arteriosus completes the transition of fetal to newborn circulations.
Tetralogy of Fallot (TOF) is an anomaly in the heart where four related cardiac defects are occurring together. These include the Overriding Aorta is the enlargement of the aortic valves which arises from the right and the left ventricles as opposed to the normal hearts where it occurs in the left ventricle only (Donald, Lopez, Hijazi. & Alboliras, 2018). The Right Ventricle Hypertrophy is where the muscular walls of the heart thicken in the right ventricle. This occurs when there is a high level of pumping of blood at the right ventricle The Pulmonary stenosis is where there is blockage of the outflow tract and the pulmonary valve which at either way narrows obstructing the right ventricle movement of blood. The Ventricular Septal Defect (VSD) is a hole which occurs between the left and the right pumping sections of the heart. It is normal for infants to have a hole between the two atria which closes after a few weeks after birth. However, VSD occurs when children are born with a hole between the ventricles (Donald, Lopez, Hijazi. & Alboliras, 2018).
The TOF is a relatively rare disease which was detected about 120 years ago and occurs in 5 out of every 10,000 births. The cause of the defect is still unknown and is known to develop in the later stages of the child before birth. (Donald, Lopez, Hijazi. & Alboliras, 2018). Approximately 15% of people suffering from TOF have been known to have a genetic abnormality which is linked to other defects such as cleft palate Once the TOF is diagnosed is prudent that the level of oxygen in the child are at safe levels. If they are critically low, there is prostaglandin infusion which is done to keep the ductus arteriosus open to induce increased pulmonary blood flow, subsequently increasing oxygenated blood into the child’s system (Donald, Lopez, Hijazi. & Alboliras, 2018). TOF corrective repair is the closure VSD by using the Synthetic Dacron Patch which results in the blood flowing from into the aorta through the left ventricle. Complete surgical repairs happen in children when they are about six months of age. Surgical operations for the defects are usually necessary, and children can be allowed to go home for a few weeks if the blood oxygen is at safe levels. In the absence of other risk factors, 95% successful TOF surgeries are done in the first year of the child (Donald, Lopez, Hijazi. & Alboliras, 2018).
References
Artman, M., Mahony, L., & Teitel, D. (2017). Neonatal Cardiology, Third Edition. McGraw Hill Professional.
Donald J. H., Lopez, C., Hijazi, Z.M., & Alboliras E.T. (2018). Visual Guide to Neonatal Cardiology. Wiley-Blackwell.
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