But when you look at the big picture of the use of tests,
those other tests may increase in another population. In
the people who have already known coronary disease. And,
as the baby boomers age, there’ll be more and more
in that age group. So it’s complex. There
still will be diagnostic applications. There still will
be a lot of use of nuclear testing. But
the first test of choice in the patient with intermediate
likelihood of coronary artery disease who has symptoms may
well become the CT coronary angiogram.
Q: What is the impact on and
the experience of the patient during multislice CT scanning?
Dr. Berman: It’s a very rapid test that
involves about 15 minutes of time, and an injection of a contrast
agent that does cause a warm sensation. There is a small risk
of an allergic reaction to this injected contrast and, in that
sense, it differs from other methods such as MRI or nuclear
cardiology technologies that also use injections but without
that risk of allergy.
The other thing that can happen is that
there’s a small risk of kidney impairment on the basis
of giving this dye, so patients who have kidney dysfunction
or abnormally functioning kidneys are approached very cautiously.
There are ways around these risks, however,
and they are very small.
There is a radiation exposure associated
with the test, but it’s similar to the radiation exposure
of other diagnostic tests. Because of the radiation exposure
we are not currently recommending that this be used as a
screening test for everyone. We would want to use a test
with less radiation unless there was a higher suspicion of
obstructive
disease. But in the future, that radiation burden may
be decreasing significantly.
Q: How do you see the future
developments in Multislice CT in terms of the ability
to use less radiation, and other advances?
Dr. Berman: In the near future, techniques to
reduce the radiation exposure will be developed. There will
be increased ability to objectively analyze the images so that
we don’t rely just on the skill of the operator of the
computer workstation And there will be improvement in technology
that may reduce the need to rely on beta-blockers to slow the
heart rate sufficiently in all cases.
Q: Which professional should
be doing Multislice CT scanning for coronary artery disease
-- the cardiologist, radiologist, etc.?
Dr. Berman: It’s going to be done by
whoever is the best trained in a given circumstance. They
will range from people who are doing catheterizations now,
to people whose specialty is noninvasive imaging to people
whose specialty is radiology with a focus on cardiovascular
imaging. I don’t think it’s so much what the
person’s area of general specialization is as much
as it is what is the person’s skill and expertise in
this specific form of testing.
Q: What about Magnetic Resonance
Angiography (MRA)?
Dr. Berman: Not going to be a player for the
coronary artery because of limitations in multiple different
problems that arise for looking at coronary arteries. MRA will
be helpful in assessing plaque in other vessels, but coronary
artery disease that is such a prominent killer can be active
at a time when disease is not active in other vessels in the
system, so it’s not as direct an approach as will be
provided by plaque imaging using the coronary artery and PET/CT.
Q: In recent years, it's become
clear that it's not just the amount of plaque, but the
type of plaque that is important to visualize. What is
the status of Multislice CT scanning right now with the
imaging of different forms of plaque?
Dr. Berman: It’s completely in the research
phase and I think it’s premature to say how that’s
going to affect patient management. Right now, the amount of
soft, of non-calcified, plaque that a patient has -- it shouldn’t
be called soft, because often it’s hard, but it’s non-calcified plaque
-- can be evaluated in CT in a way that can’t be achieved
by any other current technique in the coronary artery. Even
the diagnostic coronary angiogram can’t see the non-calcified
plaque -- it sees the lumen rather than the wall of the vessel.
We believe that in the more distant future,
we will have techniques that will allow us to assess, to
identify patients with rupture-prone plaque, which is probably
a better term than vulnerable plaque. The rupture-prone plaque
is a plaque that is associated with inflammation, a lot of
lipid disposition, and has a thin cap on the plaque. The
features of inflammation may give us a specific target that
could be used in combination with PET scanning and CT scanning
in the future.
So looking down the line, I believe that
instead of just simply saying that we’ll find patients
who have coronary obstruction, we’re going to ultimately
have the ability to separate out the people who are at very
high risk by identifying patients who have rupture-prone
plaque. I also believe that it’s going to be difficult
to do that with CT alone and it may require a technique such
PET/CT.
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