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Antonio Colombo, MD

Dr. Colombo is Director of the Cardiac Catheterization Laboratory at Columbus Hospital and San Raffaele Hospital, both in Milan, Italy and is currently visiting professor at Columbia University School of Medicine. He has authored numerous articles, is a member of both European and U.S. professional societies and serves on the editorial boards of Circulation, the Journal of Invasive Cardiology, Journal of the American College of Cardiology and several other major heart journals.

Known worldwide as one of the leaders of interventional cardiology, Dr. Colombo has developed numerous techniques and is a pioneering force in the field of coronary stent placement. In this interview, he explains how he uses intravascular ultrasound to improve the outcomes of stent procedures and reduce the incidence of stent thrombosis.

 

 

Antonio Colombo, MD
Antonio Colombo, MD **
Q: Youíve 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 donít know exactly the vessel size. And [with angiography] we canít 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 itís 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 donít 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: Weíve written an article that the use of IVUS may decrease the incidence of late stent thrombosis. Do you think thatís a valid assumption?
Dr. Colombo: I think that this is true, but itís difficult to demonstrate because we donít have a large trial with a sufficient number of patients to test thrombosis because thankfully itís 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 donít think itís difficult if you have the commitment to do that. But itís 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. Itís 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 itís 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 wouldnít 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. Itís like if you were driving a faster car. If you know what youíre doing, itís fine. But itís more prone to make a mistake if youíre 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 wouldnít make any difference.
Dr. Colombo: Iím 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 donít reach the other two steps, itís like you didnít do IVUS. I think itís 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 donít 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 thatís 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. Thatís not optimal. Itís okay Ė itís not a major mistake, but itís not optimal.

So I donít think itís so important to select the size of the stent at the very beginning. Itís 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? Doesnít 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 itís 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 thatís 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 youíre able to avoid a re-intervention, doesnít 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 doesnít 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. Theyíre 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 whatís 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 canít use Multislice CT to guide your angioplasty in the same way. In addition IVUS doesnít 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 thatís 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 donít 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 Iíve been working in this field for more than 25 years, so sometimes I assume that I know.

This interview was conducted by Burt Cohen of Angioplasty.Org on May 11, 2007
** photo courtesy of Columbia University Center for Interventional Vascular Therapy
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