the ductus arteriosus is closed. Let’s look
at our major defects. As we said, the most
common of those is the ventricular septal
defect marked in this diagram here.
It’s most common near the junction with the atrium.
Just look back at the previous slide and what
we can see is that the intraventricular septum
runs all the way up to the atrial junction.
Then in the defect, this is the part that’s
actually missing. Now, many VSDs are small,
and they may not be clinically significant.
In fact, some of them will heal spontaneously.
So the presence of a VSD is not in itself
necessarily life threatening. But you can
see that what will happen is that blood will
cross the heart from left to right.
And babies with a moderate ventricular septal defect
or VSD may breathe more quickly because the
supply of oxygenated blood is reduced by this
process. As a result, they may exhibit per
weight gain. They may also be slow to feed,
and they may be prone to chest infections
and that’s because the blood supply to the
lungs is not as rich in oxygen as it would
normally be, otherwise. And this fact can cause
cyanosis. So the lack of oxygen in the
blood can lead some of the membranes to begin
to look blue. You may see this in the fingernail
beds or in the lips. Let’s look now at the
atrial septal defect. In this diagram, you
can see in the arrows that blood is crossing
from the left atrium into the right atrium.
So it’s not making it into the pulmonary
circulation at all. Instead, it’s passing
on down into the right ventricle and going
around the heart in such a way as to avoid
the pulmonary circulation. This may be a high
level, or as in the diagram on the right-hand
side, may be at a lower level. Atrial septal
defect is sometimes associated with Trisomy
21 Down syndrome. So if you identify a child
suffering from Trisomy 21, this would be a
useful thing to look for, clinically. Again,
if it’s a minor condition, if it’s a small
hole, then it may cause no detectable problems.
Indeed, it may not be spotted until the baby
begins to walk. At that point, there’s an
increase in demands on the heart and in the
circulatory system. At this point, a defect
like an ASD, an atrial septal defect, may
become obvious. Of course, even when it’s
identified, it may be decided to defer surgery
to correct it to later. Obviously, operating
on baby’s hearts and infant’s hearts is
difficult because of their very small size
and sometimes it’s better to allow the child
to grow so that the operation can be carried out
to a later stage. Also, there are possibilities
for closing the atrial septal defect by catheterization
so that open heart surgery is not required.