Q:
You’ve been quoted as saying that you plan to use
intravascular ultrasound (IVUS) on all of your stent
cases. Why do you feel IVUS is required?
Dr. Colombo: Because I can verify an optimal implantation with good
expansion of the stent which matches the appropriate size of the
vessel and the presence of disease in the wall of the vessel. Angiography
is not the best tool to evaluate appropriate stent dilatation. Angiography
gives incomplete information because we only know the lumen size,
but we don’t know exactly the vessel size. And [with angiography]
we can’t assess if the stent is adequately dilated and well-apposed
to the media; we only know if the stent is apposed to the plaque.
But the plaque needs to be expanded at least to 70% the size of the
media. In order to achieve that, you need another tool to know exactly
the size of the media. Intravascular ultrasound will give exactly
the measurement of the media to media diameter.
Q: When a physician looks at an angiogram, he may say
that it is 50% blocked or 60% or 80%. Is it possible that it’s actually
less? Or more?
Dr. Colombo: Yes. Because you are comparing with a nearby segment
and you do not know what the true size of the artery is. If you compare
a diseased artery with another vessel which is also diseased and
is very close-by, you are basically comparing two abnormal segments.
You can tell that segment B is 50% narrower than segment A, but if
segment A is 20% narrowed, compared to a normal segment, you are
calling 50% what is, in reality, 70%.
Q: What are the implications of that, if you under-dilate
or under-correct with a stent, if you don’t expand to the full
extent of the artery?
Dr. Colombo: Then you have a stent which is in a less optimal contact
with the vessel wall. You have more turbulence. You have struts
that are not perfectly attached or embedded in the plaque, and
you may have more foreign body protruding into the lumen, increasing
the risk of restenosis and thrombosis.
Q: We’ve written an article that the use of IVUS may
decrease the incidence of late stent thrombosis. Do you think
that’s a valid assumption?
Dr. Colombo: I think that this is true, but it’s difficult to demonstrate
because we don’t have a large trial with a sufficient number of
patients to test thrombosis because thankfully it’s a low frequency
phenomenon.
Q: How difficult is it for a physician to learn how
to use and interpret IVUS?
Dr. Colombo: Physicians have learned many more complex items in
their career, so I don’t think it’s difficult if you have the commitment
to do that. But it’s certainly not something that you pick up in
a couple of days. You have to dedicate your time, look at several
cases, and you will have to invest extra time, so you must be committed.
It’s not just the simple usage of IVUS. The usage of IVUS is one
tool, but then you have to achieve the goal.
Q: Once IVUS is learned, does it take longer to perform
in the lab? Is there any extra risk, or additional time under
fluoroscopy?
Dr. Colombo: My experience is that the [additional] time under
fluoroscopy is negligible. It takes more time to do the procedure
in general, I would say about 20% more time. And we cannot say
about the risk, but I would say maybe that it’s a slightly higher
risk of complications because you are being more aggressive. I
think if you are experienced and you are very careful, nothing
will happen. But if you make a mistake, you will have complications,
so you have to be sure not to make mistakes, because you are pushing
the treatment, I wouldn’t say to the limit, but a little bit more
[than usual]. And you have to be careful to measure exactly, to
use the appropriate balloons, not to use a balloon which is too
long to do the inflation inside the stent. It’s like if you were
driving a faster car. If you know what you’re doing, it’s fine.
But it’s more prone to make a mistake if you’re not very careful.
Q: In a recent poll, half the physicians felt that IVUS
could improve the outcomes, regarding stent thrombosis, but half
felt it wouldn’t make any difference.
Dr. Colombo: I’m convinced that it will improve [outcomes] but, you
know, in medicine and science we go by data. The only element to
keep in mind, if you are doing a study, is to evaluate if the patient
with IVUS did really reach an optimal result.
Many physicians are under the impression that by doing IVUS you do
something good. You do something good if you react in the appropriate
fashion, then you improve the result. The fact that you do IVUS is
not per se any good unless you make a reaction and you achieve a
goal. So IVUS is the first step. But then you have to dilate, and
you have to achieve the appropriate result. So if you don’t reach
the other two steps, it’s like you didn’t do IVUS. I think it’s very
important not only to monitor the patient with IVUS but to monitor
what kind of result did the patient achieve following IVUS.
Q: If IVUS is important in measuring the true size of
the artery, do you use IVUS before choosing a stent?
Dr. Colombo: I think you don’t really need to do IVUS before the
stenting. Any additional information, of course, is always welcome,
but most of the time it is sufficient to do IVUS after the stenting
in order to improve the result.
So just from a practical point of view, IVUS after stent implantation
is most of the time sufficient, because the stent can be dilated.
If you implant a stent that is 2.5mm, you can still dilate the same
stent to 3.5mm. The stent is exactly the same; the only difference
is the balloon.
If you implant a stent which is 2.25mm, and then you have to expand
the stent to 5mm, then that’s a different story, because you need
a different stent. But within the range of 2mm plus/minus, the only
difference is the balloon size. The stent is actually the same. The
stent that is mounted on a 2.5mm balloon is the same as the one mounted
on a 3.0 or 3.5. You have one stent that is for 2.5mm up to 3.5mm,
and then you have a stent for 4.0 up to 5.0mm. You should not implant
a stent of 2.5 and then have to dilate to 4.0. That’s not optimal.
It’s okay – it’s not a major mistake, but it’s not optimal.
So I don’t think it’s so important to select the size of the stent
at the very beginning. It’s important to select the size of the balloon
at the very end.
Q: If the stent is not implanted close to the vessel
wall, if there is a flap or a pocket around the stent, what is it
that can happen?
Dr. Colombo: That will facilitate formation of clots inside the pocket.
And it will also impair the growth of tissue around the stent. The
tissue has to make like a jump, which is a significant undertaking
for cells. You know as well as me that the cells are very small,
so a quarter of a millimeter for one cell is a big distance. So for
cells to fill the gap of a quarter millimeter can be a pretty big
task. That means the coverage by the endothelium of the stent may
be incomplete, or not fully achieved in a reasonable time period.
Q: There was a study last year called S.T.L.L.R., which
was funded by Cordis, and it concluded that almost 2/3 of stents
are not optimally placed. Does this seem right to you? Doesn’t this
make for worse outcomes?
Dr. Colombo: It makes sense. I think that 2/3 of the stents are most
probably not well-placed. It certainly can increase the risk of restenosis
because you have a less of an optimal result. Less of a size to accommodate
whatever tissue growth you may have, which will cause re-narrowing.
Q: Does the addition of IVUS add significantly to the
cost of a procedure?
Dr. Colombo: The cost of the average catheter is not really so expensive.
I think currently it’s 500 Euros, maybe even less if you do a large
usage. You can afford IVUS.
To me, the factor to compare is the extra time and the fact that
it requires more expertise. And many people are reluctant to invest
in this extra time or to acquire extra skills. In addition, most
of the time you need an extra balloon, to do a good inflation and
to achieve a good result. And that’s an additional cost.
So the cost is the IVUS catheter, the extra balloon, the time the
patient has to stay in the cath lab, and the expertise that the doctor
needs to acquire.
Q: Of course, if you’re able to avoid a re-intervention,
doesn’t it become more cost-effective?
Dr. Colombo: Yeah, yeah. But, you know, to be practical, you are
paid for the interventions as well. So it really doesn’t affect so
much the physician. It affects more the patient.
Q: What is the best way to get training in IVUS?
Dr. Colombo: To go to courses and to spend at least one week of time
in a center where they do a lot of IVUS.
Q: There are some simulation programs on computer. Are
they helpful?
Dr. Colombo: Yeah. They’re helpful, but you need both. You need homework,
home study, you need to work with courses, and you need to spend
time to see real cases in order to be able to ask questions and confront
what’s really happening or to see what people are doing.
Q: How does IVUS compare to some of the newer imaging
technologies like Multislice CT?
Dr. Colombo: IVUS is a tool that you use while you work. Multislice
CT is a tool which could be integrated with IVUS, but IVUS is a tool
that allows you to check what you are doing in that specific moment.
So I think the two are completely different. They give you the same
information, you may say, but at two different times. You can’t use
Multislice CT to guide your angioplasty in the same way. In addition
IVUS doesn’t give you the radiation.
Q: IVUS has been around for almost 15 years. Why is it
just now becoming more well-known?
Dr. Colombo: Now people are so scared of this stent thrombosis that
they are almost grabbing any possible tool which may help to lower
this. In addition many studies are coming out showing that incomplete
stent apposition has been associated with development of late stent
thrombosis. So that’s another piece of information. Thrombosis and
the association of incomplete expansion with thrombosis is the reasons
why IVUS is gaining, is going back into practice.
Q: And you are using IVUS in all your cases, or almost
all?
Dr. Colombo: Almost all. It depends. In a public hospital sometimes
I am pushed by the schedule, by the patient load, so sometimes I
have to make some practical decision if the lesion is very simple,
I cut short. But still, having used IVUS most of the time, I have
acquired what you might call an IVUS background, an IVUS mentality.
Q: So even if you don’t use IVUS on a specific case,
your use of IVUS in general has changed the way you look at an angiogram?
Dr. Colombo: Yes. So I always think of the vessel as a little bit
bigger than the way it looks. But I’ve been working in this field
for more than 25 years, so sometimes I assume that I know. |
