Changes in Circulation
Certain changes in circulation occur at birth, and they are related to the gas exchange in the lungs and the work of the heart. Furthermore, one of the main causes of these changes is the fact that the umbilical cord becomes clamped (Hooper et al., 2015). As a result, the lungs can be viewed as prepared to breathing actively while becoming larger, and the capillary network also becomes wide to decrease resistance and increase the flow of blood.
These changes lead to decreases in the pressure observed in the right atrium (Hooper et al., 2015). Changes in the pressure also lead to closing shunts located between the left and right atrium. Furthermore, the pressure in the aorta also increases, and a right-to-left shunt begins to function as a left-to-right shunt. The increase in the pressure in the aorta leads to the creation of a functional seal because of the contractions of the musculature (Hooper et al., 2015). In newborns, this shunt typically disappears in several weeks.
There are two forms of shunts which are left-to-right and right-to-left shunts. Thus, left-to-right shunts are associated with processes when blood recirculates in the lungs. A ventricular septal defect is related to this type of shunts (Hooper et al., 2015). Right-to-left shunts are observed when venous blood bypasses the lungs. This situation can be associated with intracardiac or intrapulmonary defects (Hooper et al., 2015). The difference in these two shunts is that the right-to-left shunts affect the cardiac output and inhalational anesthetics more significantly in comparison to the effects of the left-to-right shunts.
Ventricular Septal Defect
The ventricular septal defect is a specific type of congenital heart defect which is observed when the communication between the ventricles is problematic. While discussing the pathophysiology of this condition, it is important to note that the shunting is usually directed from the left side with high pressure to the right side with low pressure (McCance & Huether, 2014). Pulmonary vascular resistance can significantly affect the degree of the problem. When ventricular septal defects are small, the resistance to shunting is high, and the flow of blood is limited.
Changes in the amount of shunted blood can be observed in several weeks after birth when the resistance associated with the pulmonary vascular function decreases (McCance & Huether, 2014). However, the left-to-right shunting associated with increases in the pulmonary flow of blood leads to decreasing pulmonary vessels’ diameters, and in this case, it is possible to observe the resistance to the flow of blood which can potentially lead to irreversible changes associated with the ventricular septal defect.
It is necessary to state that the occurrence of the ventricular septal defect is frequent while comparing it to the occurrence of other congenital heart defects. Thus, about 30% of these heart defects are classified as ventricular septal defects (McCance & Huether, 2014). Furthermore, it is important to pay attention to the fact that ventricular septal defects are divided into perimembranous, muscular, and supracristal ones, among which perimembranous ventricular septal defects are viewed as most typical. The treatment of the ventricular septal defect includes the use of the patch closure, sternotomy, a specific transarterial method, and the use of cardiopulmonary bypass (McCance & Huether, 2014). All these methods can be viewed as effective when they are applied during the first weeks after an infant’s birth.
Hooper, S. B., Te Pas, A. B., Lang, J., Van Vonderen, J. J., Roehr, C. C., Kluckow, M.,… Polglase, G. R. (2015). Cardiovascular transition at birth: A physiological sequence. Pediatric Research, 77(5), 608-614.
McCance, K. L., & Huether, S. E. (2014). Pathophysiology: The biologic basis for disease in adults and children (7th ed.). St. Louis, MO: Elsevier.