The incidence of CHD in children is generally believed to be 4 to 10 per 1000 live births and is the major cause of death in the first year( other than prematurity)
The etiology of most congenital heart defects is not known. However, several factors are associated with a higher than normal incidence of the disease. These include prenatal factors such as 1. maternal rubella
2. maternal alcoholism
3. maternal age over 40 years
4. maternal type 1 diabetes
Several genetic factors are also implicated, although the influence is multifactorial 1. If the child has a sibling with a heart defect
2. has a parent with CHD
3. has a chromosomal defect such as Down’s Syndrome
born with other, non-cardiac congenital anomalies
During fetal life, blood carrying oxygen and nutritive materials from the placenta enters the fetal system through the umbilicus via the large umbilical vein.
1. Oxygenated blood enters the heart by way of the INFERIOR VENA CAVA 2. Because of the higher pressure of blood entering the right atrium, it is directed posteriorly in a straight pathway across the right atrium and through the FORAMEN OVALE to the left atrium. 3. In this way the better oxygenated blood enters the left atrium and ventricle, to be pumped through the aorta to the head and upper extremities. 4. Blood from the head and upper extremities entering the right atrium from the superior vena cava is directed downward through the tricuspid valve into the right ventricle. 5. From here it is pumped through the pulmonary artery, where the major portion is shunted to the descending aorta via the DUCTUS ARTERIOSUS 6. Only a small amount flows to and from the non functioning fetal lungs 7. With the cessation of placental blood flow from clamping of the umbilical cord and the expansion of the lungs at birth, the hemodynamics of the fetal vascular system undergo pronounced and abrupt changes. 8. The FORAMEN OVALE closes as the pressure in the left atrium exceeds the pressure in the right atrium. 9. The DUCTUS ARTERIOSUS starts to close in the presence of increased oxygen concentration in the blood Altered Hemodynamics
As with any fluid, blood flows from an area of high pressure to one of lower pressure and toward the path of least resistance. The higher the pressure gradient, the greater the rate of flow; the higher the resistance, the lesser the rate of flow.
Classification of Defects
1. Increase Pulmonary Blood Flow
* Atrial septal defect
* Ventricular septal defect
* Patent ductus arteriosus
* Atrioventricular canal
In this group of cardiac defects, intracardiac communications along the septum or an abnormal connection between the great arteries allows blood to flow from the higher pressure left side of the heart to the lower pressure right side of the heart. (p.938)
* signs and symptoms of CHF
2. Obstructive Defects
* Coarctation of aorta
* Aortic stenosis
* Pulmonic stenosis
In this group blood exiting the heart meets an area of anatomic narrowing(stenosis), causing obstruction to blood flow. The pressure in the ventricle and in the great artery before the obstruction is increased, and the pressure in the area beyond the obstruction is decreased. (p.942)
* signs of CHF
* severe pulmonic stenosis, hypoxemia may be seen
1. Decreased Pulmonary Blood Flow
* Tetralogy of Fallot
* Tricuspid atresia
In this group of defects, there is obstruction of pulmonary blood flow and an anatomic defect (ASD or VSD) between the right and left sides of the heart. Because blood has difficulty exiting the right side of the heart via the pulmonary artery, pressure on the right side increases.
* these patients are hypoxemic and usually appear cyanotic...