Welcome back! This is Part 4 of “Cardiology:
This is going to be a continuation of our
examination of the various cardiovascular
diagnostic approaches for patients with suspected
In the previous session, we talked about the
basic beginning steps in making a diagnosis
- the history, the physical exam, the electrocardiogram.
Now, we are going to talk about more sophisticated
tests, imaging tests in particular, that will
help us diagnose heart disease and, in particular,
the commonest heart disease - atherosclerotic
heart disease, which can lead to heart attacks
and sudden death.
Here is a list of the non-invasive tests.
What we mean by a ‘non-invasive’ test,
is that we do not have to introduce anything
inside the body.
We also have invasive tests. And I will talk
about that in just a moment. And you can see
here that the basic tests are still included.
For example, the electrocardiogram, the chest
X-ray, and then we move on to more sophisticated
imaging tests such as ultrasound test, the
echo test. We move from there to X-ray, sophisticated
tests such as the CAT scan, also called the
CT scan which gives us very exquisite images
of the heart. And finally, the magnetic-resonance
imaging test, the MRI, which gives us very
detailed pictures inside the heart. And, of
course, we also can record the electrocardiogram
over a long period of time - 24 hours, 48
hours, 72 hours in order to see if there are
abnormalities in cardiac rhythm.
Let’s start with the very basic test, that
is the chest X-ray. And I will show you some
examples a little later in this talk. But,
basically, what the chest X-ray shows us…
it shows us the heart, the ribs and the lungs
and gives us a rough picture of what’s going
on in the chest, nowhere near as detailed
as the CT scan or the MRI.
There are also nuclear tests. In these, we
inject a small amount of radioactive substance
that can end up showing us damaged myocardium
or abnormalities in blood flow in the heart
depending upon how the radionuclides redistribute
themselves. These are very common tests. Even
though they involve a small intravenous injection,
we still call them non-invasive because we
don't put major catheters inside the body.
Just for an example, here we see a MRI of the
chest. You can see the black areas on both
sides of the lungs. The heart is in the middle
and the little, lighter-colored material just
below the heart is actually some fluid inside
the pericardial space. So, this MRI would
be read as a small pericardial effusion.
Now, again, we are going to talk about invasive
tests. Now, invasive tests involve introducing
catheters inside the body. We talked a little
bit about this before, when I showed you the
balloon catheter that is threaded into the
right side of the heart and it enables us
to give pressures and blood flow measurements.
But, we also do more sophisticated things
with the catheterizations. We are able to
inject dye, take X-ray movies, look at the
insides of blood vessels, the insides of cardiac
chambers. And then, of course, we can also
do recordings of the electrical activity inside
the heart. And this can actually lead to therapy,
where we actually can burn out or eradicate
areas, small areas of the heart, of course,
that lead to these arrhythmias.
Since ischemic heart disease is the most common
cause of death in… throughout the world,
both in Western Europe and in the United States
and, of course, rapidly now, it’s become
the commonest cause of death in Asia, we have
a whole series of graded tests.
You can see in this pyramid shaped, the most
basic and commonly used tests are at the bottom.
We start with the ECG, both with an exercise
or/and at rest. We move up to imaging tests
with the exercise test. For example, nuclear
or echo tests that use imaging alongside of
exercise or drugs to stress the heart. And
from there, we rarely have to do a CT or an
MRI or a plain echo because we usually get
the information we need from the previous
tests, such as the imaging tests with stress,
either exercise stress or a drug stress.