Other tests can be done to look for peripheral
vein and peripheral artery abnormalities.
Here we use ultrasound. This is similar to
the ultrasound used in pregnant women to look
at the fetus except here we’re looking
at the veins and the arteries. This technique
is very commonly used for detection of internal
carotid artery atherosclerotic plaques and
obstruction. And as you see in the little
cartoon, there’s obstruction there. And
then in the next slide you can see that one
can actually estimate the degree of stenosis
because the picture shows us the internal
lumen or channel of the carotid artery with
an obstructive atherosclerotic plaque. It
has been shown in many studies that the worst
the narrowing in the carotid arteries the
greater the risk for stroke for that person.
And then one needs to do something about it.
Of course there’s medical and surgical and
catheter therapies for this. And that’s
the subject of a later discussion.
Black and white imaging is done as you saw
on the last slide. And you can usually tell
if the plaque is greater than 50%, approximately
50% or less or whether in fact the artery
is completely blocked.
When we use it in the venous system, it also
shows us whether there’s normal blood or
whether there’s an obstruction in the flow
of blood in the veins. In other words a blood
This is a colour Doppler flow map of a vein.
The different colours show you the velocity
of flow, the red being high-velocity flow.
So here we see a very normal vein with lots
of blood flowing, turbulent blood at one point
probably because there’s a bifurcation or
a bridging of two veins that come together
in a place which creates a little turbulent
flow. What we can see when there’s a clot
there is that the flow stops. And you can
see clearly in this picture, you can see blood flow up
to a certain point in the vein and then suddenly
none and then beyond it downstream no blood
flow. We also can actually look at patterns
of the blood flow. And there are abnormal
wave forms versus normal wave forms.
This slide shows you abnormal wave forms that
are associated with decreased blood flow velocity
beyond an area of obstruction. And you can
also see that there is no flow detected below
the point of obstruction. This is used for
the diagnosis of venous thrombosis – or
a blood clot – in the legs, a very common
condition which will also be discussed in
a subsequent lecture.
Here we actually see the blood clot visualised
in a vein. And the Doppler shows the flow
and this image just shows you that there’s
a clot in the vein.
We can also use the venous and arterial ultrasound
imaging techniques to show us areas of the
artery or vein that are abnormal, markedly
dilated or increased in size.
Here we see an aneurysm – that is an outpouching,
a weakening of the wall in the abdominal aorta.
And you can see how large and round this is.
These entities can actually rupture and be
fatal. And so we follow them very closely
with periodic ultrasound studies. And you
can see that there’s only flow in part of
this aneurysm in the lower left-hand figure
because the rest has clots in it, which is
another complication of the aneurysm.
I mentioned before that atrial fibrillation
puts patients at risk for developing blood
clots in the heart that can break off and
cause a stroke or kidney damage. And what
you see here is using a two-dimensional echocardiogram
put into the esophagus. We can actually see,
where the arrow is, that there’s a blood
clot sitting in the left atrium ready to break
off and cause a stroke. This is of course
an indication for anticoagulation – that
is blood thinners – to prevent this clot
from getting bigger and, eventually, letting
the body dissolve it.