Complex Congenital Heart Defects:

Tricuspid Atresia, Hypoplastic Left Heart, and Single Ventricle.

Congenital Heart Defects

Additional Information and summary:

Normal Heart Circulation

Below is a diagram of the blood flow in a normal heart circulation.


Overview of the Fetal Circulation

When the baby is in its mother's womb, its circulation is different and only uses primarily one side of the heart, which is why many of these heart defects do not become apparent until the baby is born. As it can be seen in the diagram below, the fetal circulation mainly relies upon the right side of the heart and very little blood is passed into the lungs because the blood is reoxygenated via the mother's placenta when it is in the womb. There are two main differences in the anatomy and function of the fetal heart as opposed to the heart of a regular child. The main difference is a connection between the aorta and the pulmonary artery that exists called the DUCTUS ARTERIOSUS. The 2nd difference is the existance of the FORAMEN OVALE when the child is a fetus. The foramen ovale is an opening between the right and left atrium where blood can pass.

Ductus Arteriosus

The ductus arteriosus connects the aorta and the pulmonary artery while the baby is a fetus. Because the pressure in the lungs is so high when the baby is a fetus, the blood travels into aorta via the ductus arteriosus instead of continueing down the pulmonary artery to the lungs. Once the baby is born, the ductus arteriosus closes off anywhere from within the first few hours to a few weeks after birth.


Notice that the baby does not use its lungs and only very little blood enters its lungs via the pulmonary artery. Most of its blood is sent to the body and then through the umbilical cord to the PLACENTA to be reoxygenated by the mother. The venus blood then enters into the blood on the way to the heart, deoxygenating the blood a little.


Tricuspid Atresia

In tricuspid atresia, there is no tricuspid valve formed or the triscupid valve is very obstructed. This means that blood cannot flow from the right atrium to the right ventricle (which pumps blood to the lungs). Therefore because of tricuspic atresia, the blood becomes less and less oxygenated.


Hypoplastic Left Heart

Hypoplastic left heart syndrome is one of the most severe heart defects. In the hypoplastic left heart defect, the left side of the heart is poorly developed and is not capable of handling the circulation of blood to the body. Once the ductus arteriosus closes, if corrective measures are not taken, death is the result.



Single Ventricle Defect


The Single Ventricle Defect is basically when there is no ventricular septum that divides the left and right atrium. The left and right ventricle act as one ventricle, mixing the blood and pumping out deoxygenated/oxygenated blood. There are three variations of single ventricle defect: balanced circulation, obstructed pulmonary artery, and normal pulmonary artery.

Obstructed Pulmonary Artery:

When someone has an obstructed pulmonary artery with a single ventricle defect that means that there is an obstruction in the pulmonary circulation (examples: thickened pulmonary artery , or tissue blockage around the valve).

Problem.....Since there is some kind of blockage, that means that the blood has a harder time flowing into the pulmonary artery and therefore less blood flows to the lungs. Because of this obstruction, blood flows more easily into the aorta and to the rest of the body. However, because less blood flows to the lungs, less blood gets oxygenated. As time progresses, there is LESS and LESS oxygen entering into the child's blood stream leading to CYANOSIS, the major indicator of this defect.



Normal Pulmonary Artery

When someone has a normal pulmonary artery and the single ventricle defect, more blood flows to the lungs than to the rest of the body. The lungs vessels respond by thickening its walls, therefore allowing less and less blood to flow through. If this condition is not caught and treated, the lung vessels can eventually narrow to the point that very little blood is entering the lungs to be oxygenated. If it reaches this point, the defect is often fatal.


Slightly Obstructed Pulmonary Arter

In the single ventricle defect with only a slightly obstructed pulmonary artery, this means that there tends to be an even flow of blood to the body and the lungs. Slight obstructions may include a slight narrowing of the pulmonary artery or a little muscle tissue obstructing the pulmonary valve. Since there is an even flow between the body and lungs enough blood is oxygenated and the body gets enough blood. Therefore, often times this type of defect is harmless and not easily detected because the only problem is a slightly lower level of oxygen in the blood.