STRUCUTRES NORMAL FOR FETUS BUT NOT FOR ADULT LIFE
There are certain findings that are normal for a fetus but not necessarily in the infant. Those structures cannot be diagnosed as being abnormal in utero. Two such structures are :
Patent Ductus Arteriosus:
What is a PDA ?
PDA stands for a patent ductus arteriosus. This is a structure normally present in all fetuses. It connects the 2 great tubes/arteries coming out of the heart.
What is the role of a PDA in a fetus ?
The PDA allows blood to flow from the pulmonary artery into the main artery the aorta. The reason for this is the blood does not need to go into the lungs because the lungs are non-functional (baby is not breathing when inside the mother).
What happens to the PDA in normal newborn babies ?
Each one of us was born with a PDA. It closed some time after we were born. It usually closes in the first few days of life to first few weeks of life. The stimulus for closure is oxygen levels in blood. This level is higher after birth and stimulates the PDA to close.
ATRIAL SEPTAL DEFECT:
What is the atrial Septum?
Atrial septum is the wall between right and left atria which keeps systemic return (blue blood without oxygen) and pulmonary return (red blood with oxygen) separate.
What is a defect in the atrial septum ?
Atrial septal defects represent a communication between the left and right atria.
Is there normally a “hole in the atrial septum” in the newborn ?
Usually there is a communication between the upper chambers called foramen ovale in the fetus. This is essential for the survival of the fetus. (See Fetal Circulation).
What happens to foramen Ovale ?
This has been discussed under PFO. Majority of the PFO’s close. Even if they dont, this is not considered abnormal in children and adults.
What are the types of ASD ?
We will consider three major types of atrial septal defects:
What is a secundum atrial septal defect ?
Secundum atrial septal defect is by far the most common, representing 80% of all ASD’s. It is caused by the failure of a part of the atrial septum to close completely during the development of the heart. This results in an opening in the wall between the atria (a “hole” between the chambers). This hole is usually relatively “central” in location. These are the holes which can be considered for device closure; many of them still will not be eligible for device closure. In comparison, the Primum and Sinuns Venosus cannot even be considered for this option and have only a surgical option available, which is a very good option.