Conversations with Experts: Bare-Metal Stents in the Current Practice Landscape | CardioSource WorldNews Interventions
With Habib Samady, MD, and John Wang, MD, MSc
In this edition of our "Conversations with Experts" series, Habib Samady, MD, director of interventional cardiology and the cardiac catheterization laboratory at Emory University Hospital in Atlanta, speaks with John Wang, MD, MSc, chief of the cardiac catheterization laboratory at MedStar Union Memorial Hospital in Baltimore, about the current and future role of bare-metal stents in the interventional cardiology landscape. Dr. Wang was the national principal investigator of the OMEGA trial, the results from which led to the FDA approval of the REBEL™ Platinum Chromium Coronary Stent System (Boston Scientific Corporation; Natick, Massachusetts).
John Wang, MD, MSc: Dr. Samady, let me first ask you: what percentage of the time do you use drug-eluting stents versus bare-metal stents in your practice?
Habib Samady, MD: At Emory University Hospital, we probably use drug-eluting stents 85% of the time and bare-metal stents 15% of the time.
Dr. Wang: That's almost exactly our usage as wellabout 15% of the time, we use a bare-metal stentand this has been consistent for the last few years.
Dr. Samady: Thinking back, there was certainly an early period of exuberance following the adoption of the CYPHER® sirolimus-eluting stent (Cordis Corporation; Bridgewater, New Jersey) and other drug-eluting stents, but that was followed by the initial scare of stent thrombosis. When that hit us, I think there was a decline in drug-eluting stent usage, followed by a more thoughtful choice of stent type.
Looking at the more recent data regarding 12-month stent thrombosis, there is probably not a significant difference between bare-metal and drug-eluting stents, but there are other advantages to consider when deciding between either stent type. The advantage of drug-eluting stents, for instance, may be limited in a patient with a very large caliber vessel and a focal lesion. There are a couple of other subgroups that I think tend to receive bare-metal stents, or patients in whom we need to restrict dual antiplatelet therapy for a variety of reasons, such as those with very large vessels.
Dr. Wang: In most people's practices, including mine, the decision will come down to the patient. When we are faced with a patient who we know is clearly noncompliant with their medications those for whom we do everything we can, including provide their medicines for them upon dischargeI think it is safer to use a bare-metal stent and to minimize the dual antiplatelet therapy. Elderly patients on warfarin or a novel anti-Xa inhibitor who are at an increased risk for bleeding also should be very cautiously approached, and should probably be given a bare-metal stent.
Finally, patients who may need to discontinue dual antiplatelet therapy for planned surgery also fall in the bare-metal stent subset. Dr. Samady: With respect to dual antiplatelet therapy, it seems like we have been heading to a shorter duration in the last 4 or 5 yearsespecially with acute coronary syndrome patients who may have received one or two stents. Some recent data may even suggest that dual antiplatelet therapy beyond 12 months has no real benefit but does lead to adverse effects.
In Europe, some physicians are very aggressive and prescribe only 3 months of dual antiplatelet therapy; in the United States, we are a little more conservative and have greater concern for the rare cases of late or very-late stent thrombosis. The move towards shorter duration of dual antiplatelet therapy will really put the onus on bare-metal stents.
Dr. Wang: I think we have to ask, "Why hasn't the number of bare-metal stents decreased?" Until we can develop a drug-eluting stent which only requires 1 month of dual antiplatelet therapy, the need for bare-metal stents will always exist. Historically, we also used bare-metal stents when we could not deliver a drug-eluting stent to the lesion. First-generation drug-eluting stents were less deliverable, we were limited in the techniques we could use, including upsizing our guiding catheter or using "buddy" wires to deliver stents, with bare-metal stents saved as a kind of "last resort," in these cases. However, newer-generation drug-eluting stents are so much more deliverable, and with tools like guide extension catheters, it is rare to be unable to deliver a drug-eluting stent to the target lesion and need a bare-metal stent.
Dr. Samady: When you are choosing a stent platform for the subtypes of patients we mentioned, what characteristics do you look for?
Dr. Wang: For bare-metal stents, one of the most important characteristic to me is good radial strength (which is potentially a more important consideration for bare-metal stent than drug-eluting stents). The lack of recoil or the ability of the stent to maintain its size after the balloon is inflated and deflated is perhaps the most important consideration. Strut thickness, of course, is important, and I believe thin struts clearly are going to make a difference in terms of the conformability and the deliverability of the device.
Another factor that I think is unique to the OMEGA study and the REBEL™ commercialized stent is visibility. REBEL™ is a very visible stent. There seems to be a tradeoff occurring with many other stents: a thinner strut means less metal, but this also means it is less easily visualized. I often find myself doing a short cine burst to make sure that my post-balloon markers are within the stent, and that's because I can't see the stents very well under fluoroscopy. I can tell you that with the platinum-chromium platform employed in the REBEL™ stent, the metal clearly makes a difference in visibility, which could potentially translate to better outcomes by reducing geographic miss.
Dr. Samady: I agree, we used to pay less attention to stent platforms, but now it has become more of a consideration, and there are plentiful data on these different platforms to inform our decisions. I agree about recoil, because I think we forget that recoil is an important aspect of restenosis. From the biomechanical standpoint, there's a tradeoff between radial strength, strut thickness, and the amount of metal in your platform. With the platinum- chromium platform and some of the other materials, you could potentially "have your cake and eat it too" with a radially-strong stent and a thin strut.
The issue of conformability is more and more important, particularly for angulated vessels. When placing a stent in a straight vessel, the conformability is, understandably, less critical because it is easy to deliver and there is not a risk of creating biomechanical problems with angulation at the proximal and distal edge of the stent, comparing to an angulated vessel. The issue of strut placement is also a very important determinant, as well as healing and perhaps even restenosis.
Thinking about strut thickness, the issue is that the thicker the strut, the greater the fluid that's surface proximal at the inflow and at the outflow. There appears to be a relationship, at least biologically, between thicker struts and more aggressive response, which may be more relevant, as you said, in the bare-metal platforms than in the drug-eluting stent platform.
Compliance of these metallic platforms are also becoming more and more relevant as we move toward thinner strutsparticularly with bare-metal stents. A noncompliant device in angulated vessels will likely result in very severe solid forces on the inner curvature of the vessel; if there is a relatively soft plaque, then, it may extrude and potentially cause more plaque prolapse in the inner curvature, which again may affect flow dynamics and healing.
Dr. Wang: Somehow, having good radial strength has been equated with stiff, nonconformable stents, and I think it's very important that those are two separate issues. For some interventionalists, this is a misconception that they have internalized after years and years of using the CYPHER® stent; they associate big bulky, stainless steel stent struts with good radial strength, but the CYPHER® stent lacked conformability and many very tortuous vessels were straightened out into gradual curves. There can be both fantastic radial strength and incredible conformability, as evident by not only the REBEL™ stent but its drug-eluting counterpart (the Promus PREMIER™ Everolimus-Eluting Platinum Chromium Coronary Stent System; Boston Scientific; Natick, Massachusetts).
Dr. Samady: Speaking of the REBEL™ stent, as the national principal investigator for the OMEGA trial, could you talk about the questions you were trying to answer with the trial, and the attributes of these newer bare-metal stents?
Dr. Wang: Well, in our field, there seems to be a fairly rapid process of iterative changes in terms of drug-eluting stents, yet we haven't seen that same progression with bare-metal stentsperhaps because they do not have the same allure as drug-eluting stents, and certainly not the same market share.
To me, the REBEL™ commercialized stent that we evaluated in the OMEGA trial is the latest bare-metal version of one of the best drug-eluting stents available. We have finally developed bare-metal stents that keep pace with their drug-eluting counterparts. The very attributes that make the Promus PREMIER™ stent an excellent choice (its radial strength, its conformability, etc.) are the factors that also make REBEL™ a great bare-metal stent.
Dr. Samady: Let me ask you about that. I agree that the Promus PREMIER™ is a great stent platform, but there are no head-to-head trials comparing bare-metal and drug-eluting stent platforms from all three major manufacturersare they comparable?
Dr. Wang: It depends on how you define "comparable." If you look at acute performance, I think there will be subtle differences in deliverability, but not dramatic differences. Right now, there are very good drug-eluting stents from all three manufacturers, but in my opinion, the platinum-chromium platform used in the REBEL™ system is the winner because of its radiopacity.
The REBEL™ stent was approved based on results from the OMEGA triala single-arm study looking at 328 patients at 37 sites throughout Europe and the United States. Patients had single de novo coronary lesions and received the REBEL™ stentwhich was called the Omega stent at the time (See Editor's note below).
Using objective performance criteria as the control, we evaluated the rate of target lesion failure at 9 months with patients receiving the Omega stent. At 9 months, the objective performance goal was 21.2%, while the rate of target lesion failure was only 11.5% for the Omega stent.
I think this is an exciting studyeven though it was not very large, it certainly provided encouraging results, outperforming historical controls and the bare-metal stents previously available.
Dr. Samady: That is very exciting, and there's no question that these newer platforms that combine the advantages of a thinner strut with better radiopacity and better conformability outperform the earlier-generation stents. Well, I'd like to congratulate you on this study, and thank you for joining me in discussing the topic of bare-metal stent platforms.
Editor's note: REBEL™ and OMEGA™ are both platinum-chromium coronary stent systems. REBEL™ stent has extra connectors on the proximal end and an enhanced delivery system with a shorter tip and more lubricious catheter coatings.
DISCLOSURES: This material was sponsored by Boston Scientific Corporation.
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