I am now going to ask
you some questions that
relate to which diagnostic test to use and
under which conditions. And I hope that you
won’t immediately jump to the answer, but
that you will think about your answer and
then see what my answer is.
So, here is the first question. This is a
patient who is 90 years old, who comes to
the hospital complaining of some chest discomfort
and has a slightly abnormal electrocardiogram.
This patient lives in a nursing home and has
severe dementia, in other words - doesn’t
know family, doesn’t answer questions, doesn’t
know where they are. Would it be appropriate
to take this patient to the catheterization
laboratory? Well, this is in part an ethical
question, which the family and the patient
have to discuss. But in general, I think we
probably would not take this patient to the
catheterization laboratory because it’s
very unlikely we are going to make any improvement
in this patient’s quality of life. They
are already severely injured in terms of their
severe advanced dementia. It’s unlikely
we would make any benefit for this patient
by doing a heart catheterization. Here’s
the answer to this one that I just said. It’s
unlikely we would improve this patient by
doing a heart catheterization.
Now, in this next slide, the question occurs
- should we do two tests that give us the
same information? And the answer is obviously,
no. We wouldn’t want to do that, so you
wouldn’t need both a CT angiogram, for example,
and a cardiac catheterization. They would
give us the same answer. If we did a CT angiogram
and the images weren’t good and we weren’t
sure, of course, we might go on to an angiogram.
But, in most cases, you will just do one test
that gives you the answer. You don’t need
to do two tests.
Another example would be a patient who
had a completely negative stress test. Would
you rush off and do a cardiac catheterization?
Unlikely. Occasionally, you might if there
were some question in the stress test as to
how accurate it were... the images were. But
in general, you won’t do another stress
test or another catheterization test in a
patient where you are pretty sure already
that this is not ischemic heart disease.
And again, before ordering any test, review
in your mind the patient’s clinical information
and exactly why you are doing the test. Do
we really need this test? Is this going to
give us an answer that’s going to change
our approach to the patient, particularly
with therapy? If it’s not going to change
anything, don’t order the test. You are
wasting money and you are putting the patient
albeit at a very small risk of some complication.
Again, remember that when the patient has
already had a test that’s negative, you
don’t need further testing. So, if you do
an angiogram on a patient and the coronaries
are normal, you don’t need a stress test
to follow that because you already have your
answer. One test has given you enough information
that you don’t need further testing.
Just to remind you, you should always think
before ordering a test. This point I have
made several times, but it’s absolutely
important and it is frequently ignored. Are
we really going to do something different
based on the results of the test? In other
words, don’t ask a question that makes no
difference. You don’t need to order a test,
if you already have the answer.
If a patient has some chest discomfort and
you do a nice stress nuclear test and it’s
completely normal, you almost certainly don’t
need to order a CT angio afterwards. You already
have your answer. There is no ischemia in
this heart. Even though the stress test is
not perfect, it still strongly suggests that
this patient does not have ischemic heart
disease. And a CT angiogram would only give
you the same result again. You would be doing
two tests that would give you the same answer
and not worth doing.
Here’s an example of where a very simple
test can give you a lot of information. You
have a patient that has chest pain. We are
concerned - does this patient have a STEMI
or an ST-elevation myocardial infarction -
a heart attack of significant size or do they
have a non-ST-elevation myocardial infarction -
a smaller infarct? Well, one of the tests
that we can do, and we often do this in the
Emergency Room, is we obtain a transthoracic
echo. If the wall motion, that is the contraction
of the heart is completely normal, it’s
much, much less likely that this patient is
having a heart attack. Certainly not an ST-elevation,
substantial-sized heart attack and probably
not even a small non-ST-elevation myocardial
infarction, because almost always these are
associated with decreased areas of wall motion -
decreased contraction of the heart in certain
regions. So, that’s very helpful. The patient
comes in, has an electrocardiogram that’s
somewhat confusing and this happens all the
time. They have a story that’s somewhat
confusing. You think, “Are they having a
heart attack? Are they not?” The echo is
a very helpful test. If it’s completely
normal, the patient’s not having a heart
attack. You can move on to consider other
And here, we see just what I said to you.
If the echo image is completely normal, it’s
very unlikely that the patient has had an
ST-elevation or a non-ST-elevation MI. Of
course, if there are wall motion abnormalities,
then we have to go further in exploring the
possibility that the patient’s had a heart
This question asks - which is the best test
for demonstrating ischemic heart disease?
Well, of course, the absolutely best test
is an invasive cardiac catheterization, but
that carries some risks with it. Consequently,
what is the best non-invasive test? The best
non-invasive test is one that goes with imaging.
It turns out that the echo stress test and
the nuclear stress test are about equal in
terms of their ability to define this disease.
They are not 100% accurate, but they are in
the neighborhood of 85-90%, which is pretty
good when you combine that with your clinical
impression. You can usually decide, “Yes,
I think this patient is having problems from
ischemic heart disease or not.” The MRI
and the CT are a little less helpful because
the CT might show you some atherosclerosis,
but you don’t know if that’s causing the
patient’s symptoms. You would like a stress
test, you would like to bring out the symptoms,
if you will. You would like to see the physiology,
the abnormal physiology of lack of blood flow
in the heart, either because of abnormal wall
motion with the echo or because of abnormal
blood flow distribution with the… with the
myocardial perfusion imaging.
And this slide just shows you what I just
said that the imaging tests give you the most
information, short of the invasive cardiac
catheterization. And by the way, sometimes
after the cardiac catheterization, we go on
to do a stress test because we see some atherosclerosis
in the coronaries, but we are not sure that
that’s really causing a lack of blood flow.
And so, sometimes we will do a stress test
afterwards with an imaging study to see what’s
the implication of some more moderate amounts
An important point to remember is the test
you pick will also need to be integrated in
your thinking about the patient. What were
their symptoms, what’s their age and gender?
It turns out that older people often can’t
exercise enough to get a good increase in
heart rate and blood pressure to really stress
the heart, so you may order a drug test which
can help show also abnormalities in blood
flow in the heart.
And so, again, there has to be some thought
that goes into selecting which test you are
going to do based upon the patient’s clinical
presentation and also their age.
Just another example, a patient with bad arthritis.
You certainly shouldn’t send for an exercise
test because they are not going to be able
to walk sufficiently hard or bicycle sufficiently
hard because of their arthritis.
I mentioned before, the CT scan to look for
calcium in the coronary arteries. This is
a very good screening test. It turns out it’s
a CT, or CAT scan that uses fairly low levels
of radiation. So, the patient doesn’t get
too much radiation. And what you do here is,
if you see calcium, it means that the atherosclerotic
process has begun in the coronary arteries.
If you see a small amount of calcium, it means
there’s probably not a lot. If you see a
lot of calcium, it means that there’s probably
significant atherosclerosis in the coronary
arteries. But, it doesn’t tell you whether
there’s obstruction in the coronaries because
the atherosclerosis could be around the rim
of the coronary artery, but the channel of
the artery could still be wide open. So, we
sometimes will combine a CT scan that shows
a lot of calcium with some form of stress
test or you might even, if you are very suspicious
for coronary disease, go on to an invasive
test. But, all this tells you is the burden
of atherosclerosis. It doesn't tell you, is
the atherosclerosis really interfering
with blood flow in the coronary arteries.
Now, sometimes we get a false positive test.
What does that mean? That means the test says,
“Oh! I think there might be ischemia in
this heart.” But in fact, it turns out,
it’s not true. There are a number of reasons
for false positive tests. Particularly with
the electrocardiographic exercise test, there
can be about 10-15% false positives. The test
has ST-segment depression, like I showed you,
but in fact, when we do either an imaging
test or a catheterization, the coronary arteries
Sometimes it has to do with slight differences
in metabolism of the blood vessels and the…
and the myocardium. Sometimes it has to do
with the inability of the blood vessels in
the heart to dilate normally with exercise.
But, it doesn’t mean that the patient is
at high risk for a heart attack. So, sometimes
we will see a false positive and we will have
to follow that up with a more definitive test.
So, an example of this is the 55-year-old
woman who had a… some sort of chest pain
syndrome, sort of atypical. You send her for
an exercise test, it comes back positive.
But subsequently, an imaging test of the blood
flow on the heart shows that there is not
ischemia, that this was a false positive test.
Also, since a number of these tests give the
same results, it’s important to know how
well the test is done in your hospital. Let
me give you an example.
Some years ago, I was at the University of
Massachusetts Medical Center. We did a drug
test with imaging... with nuclear imaging using
a drug called Persantine. And it showed distribution
of blood flow in the heart when the radionuclide
was given and the images were taken. Well,
the person who invented this test and who
described it in a very excellent article in
the New England Journal was a fellow named
Jeffrey Leppo. He was head of nuclear medicine
at our place. We got more information when
he read the test than if somebody in another
hospital had read the test. So, we ordered
a lot of these tests and then we would go
down and talk to Jeffrey. He could squeeze
more information out of the test than we could
get from having somebody else look at it.
Why? Because he knew the test better than
almost anybody else in the whole world.
So again, there’s going to be some reason
to pick one test in your hospital versus another
and it’s going to depend upon how expert
the people are who are reading that test.
So, in conclusion then, we have talked about
a number of approaches to making cardiac diagnoses.
Some of the tests are quite expensive and
quite sophisticated. And others are much more
basic and much less expensive. Which test
you pick depends upon a whole variety of clinical
factors - the age of the patient, the gender,
their symptoms. You have to integrate all
the clinical information to decide what’s
the best test. And of course, you also have
to know what’s the best test in your hospital.
Remember, never order a test if you don’t
care what the result is. Whether the test
is positive or negative, you are going to
do the same thing? Then certainly, don’t
go ahead and order a test for which you have
Thank you for being with me today.