the body dissolve it.
Nuclear tests: I’ve already shown you one.
That was the lung scan. But there are also
nuclear tests to show us abnormalities in
the blood flow in the heart. So we already
talked about the first one which was lung
scanning for pulmonary embolism. The ones
that are used for the heart are several.
There’s one called the technetium pyrophosphate
scanning than can show damaged or dying heart
Thallium imaging can show us abnormality in
heart blood flow.
A MUGA scan can show us how well the heart
And a less common test – the positron emission
tomogram – can actually show us areas of
the bodies where there are abnormal structures
such as cancers. This is a test commonly used
by the oncologists – by the cancer experts
– to pick up metastases, that is spread
of cancer. The positron emission tomogram
can also be used to measure blood flow in
the heart to find areas of abnormal blood
flow secondary to atherosclerosis.
One of the commonest tests done is the so-called
stress test. Usually, this test is done with
an electrocardiogram but it can also be done
with radioactive injection, both of which
show us abnormal blood flow in the heart.
During the stress test, one exercises the
patient. You can see the little cartoon here.
It shows the patient with the EKG electrodes
on. There are technicians and a cardiologist
monitoring the test, watching on a TV screen
the EKG complexes, the electrical activity
in the heart – looking for abnormalities
that might develop that would show there are
areas of the heart not getting enough blood
flow. One can do this on a treadmill walking
or pedalling on a bicycle. And you keep increasing
the vigour with which the patient exercises.
So you, in a sense, stress the heart. You
push the heart and look to see how the heart
responded to exertion. Are there areas of
abnormal blood flow suggested?
Finally, I showed you an example before of
a transoesophageal echo. That’s an echo
probe placed on a device that actually is
threaded down into the oesophagus. But you
can also do this test from externally on the chest
wall. We do this test all the time for heart
disease. It tells us if the valves are normal,
if the muscle is working well, is the heart
dilated or not. And, as I showed you before
with the transoesophageal echo, we can actually
identify blood clots in the heart that are
at risk for breaking off and causing trouble.
A piece of blood clot that breaks off and
travels in the body is called an embolus.
We already talked about clots breaking off
from the veins in the leg causing pulmonary
embolism. But you can also have arterial embolism
where a clot breaks off from the left atrium
in a patient with atrial fibrillation and
causes a stroke.
We get a very quick assessment of heart valves
and heart contraction with the transthoracic
test. We get an idea of how vigorously the
heart is contracting. And this helps us detect
heart attacks, enlargement or weaknesses in
the heart and even cardiac tumours.
The transoesophageal as I already mentioned
is an alternative way. It gives us even better
pictures than the transthoracic. A specialised
probe is passed down the oesophagus. And you
already saw an image of a blood clot in the
left atrium in a patient with atrial fibrillation.
Finally, the invasive tests. I’ve mentioned
them before. In the invasive tests, a catheter
is threaded into a blood vessel and dye is
usually injected with this catheter so that
this dye appears white to the x-ray. And we
actually make x-ray movies showing us the
channel of a blood vessel to see whether it
has been narrowed or not. One also makes certain
measurements of blood flow and pressure in
the heart that also help tell us something
about how accurate the heart is. The overall
technique is called a catheterisation.
We can also do blood tests when we’re in
the different chambers of the heart to see
what the oxygen level is, just to make sure
it’s normal. And we can even take a little
piece of the heart muscle and send it to pathology
to be examined under the microscope if we
think there’s a tumour there or if we think
there’s some other material that’s been
deposited in the heart and that’s hurting
And these are all of the techniques that are
done invasively. We can do an angiogram of
the carotid arteries. Usually, as I said,
we start with a non-invasive test but if we
see a critical narrowing and we think about
angioplasty – that is the balloon and stent
opening of the vessel – or surgery, often
an angiogram will be done to give us a better
picture of the anatomy before surgery. And
carotid stenting actually place a little metal
cage in the artery and expands the area of
narrowing and holds it open.
We can also do electrophysiological studies
inside the heart. The electrocardiogram just
shows us the heart electrical activity from
the surface. When we put catheters in the
heart, we can get a lot more information about
the electrical activity in the heart.
And then finally we can also put a little
ultrasound probe on the tip of a catheter
and we can use that to show us the thickness
of a blood vessel and areas of atherosclerosis.
And then finally, only occasionally, we can
take a piece of heart muscle with a biopsy
to send, as I said, to pathology for examination
under the microscope.