Our next defect is the tetralogy of fallot,
whereas, in the previous ones, we looked at
the ventricular septal defect, which is a
defect of the partitioning of the ventricles.
Atrial septal defect is a defect of partitioning
of the atria. The tetralogy of fallot is a
defect of septation in the truncus arteriosus
in the outflow tract from the heart.
It’s called tetralogy because there are four major
consequences, and these overlap with each other.
So it’s hard to look at them in isolation.
So try and hold an overall picture in your
mind of what’s happening as a result of the
disturbance of septation in the outflow
tract of the heart.
The first one is identified in the diagram
as an overriding aorta. So the entrance to
the aorta is enlarged and spreads out more
than it would be, normally and this may be
visible in ultrasound views. You generally will
find a ventricular septal defect although
this may be harder to see because of the overriding
aorta in a four-chamber view of the developing heart.
There will also be a narrowing stenosis,
as we call it, between the right ventricle
and the pulmonary artery. This pulmonic stenosis
makes it harder for blood to leave the ventricle.
As a consequence, the muscle of the right
ventricle may be overdeveloped. So, you have
right ventricular hypertrophy as a consequence
of that pulmonic narrowing, that pulmonic
stenosis leading into the pulmonary circulation.
Now then, what about patent ductus arteriosus?