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Will Abbott's Absorb Bioresorbable Vascular Scaffold Revolutionize Treatment of Coronary Artery Disease?
We Discuss This Question with Three Leading Interventional Cardiologists
in the Second Part of This Two Part Feature
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Abbott's Absorb Bioresorbable Vascular Scaffold
Abbott's Absorb BVS
July 24, 2016 -- The U.S. Food and Drug Administration granted approval to Abbott's Absorb™ Bioresorbable Vascular Scaffold (BVS) a little over two weeks ago and immediately media outlets across the country were touting "the disappearing stent" as a "revolution" in the treatment of coronary artery disease.

There's no question that the concept and tremendous engineering (both biochemical and physical) that went into the creation of this device were revolutionary and innovative. But will the Absorb BVS truly change the way cardiologists treat patients with arterial blockages? That hasn't been the case in Europe where the Absorb BVS has been available for four years, and adoption is estimated at less than 10% of cases.

Drs. Ajay Kirtane, James Blankenship, and Daniel Simon
Drs. Ajay Kirtane, James Blankenship, and Daniel Simon

In Part One of this feature, we reported on the various positives and negatives of the BVS, as presented to the FDA panel that recommended approval. In Part Two, we discuss the Absorb's potential impact in the United States with three leading interventional cardiologists: Ajay J. Kirtane, MD, SM, Director of the NYP/Columbia Cardiac Catheterization Laboratories and Co-Director of the annual TCT conference, the world’s largest educational meeting specializing in interventional cardiovascular medicine; James C. Blankenship, MD, MHCM, FSCAI, MACC, Director of Cardiology and of the catheterization laboratories at Geisinger Medical Center in Pennsylvania and immediate past-president of the Society for Cardiovascular Angiography and Interventions (SCAI), the professional society for interventional cardiologists; and Daniel Simon, MD, interventional cardiologist and, as President of University Hospitals Case Medical Center in Cleveland, an administrator who must deal with cost issues.

What are the major advantages of a "disappearing stent?"
Kirtane: From an intuitive standpoint, if you have a device that does what it needs to do for the time period that it needs to do it and then goes away, that can presumably be advantageous. The key things that need to be seen are late adverse events. We know that with bare metal stents, first and even second generation drug-eluting stents, there is an accrual of events that occur within the stented segment over time.

"...make no mistake. You cannot shorten DAPT with BVS"
-- Kirtane
So if this can be shown to be reduced with this type of platform, then that would be advantageous. But at this point it's speculation because we don't have the long term follow-up from these randomized trials like ABSORB III at this point. We have just short and intermediate term outcomes.
Simon: One could make arguments that (1) lack of caging of the vessel would improve vasomotion and reduce angina - that has not been shown; (2) if you have lack of caging in a vessel and the stent disappears, that you don't have the late events that you see out to five years with respect to target lesion revascularization - that has not been shown.
Blankenship: What Abbott is hoping is that once you get to two years, that there have been no adverse events associated with that lesion or that stent because it's gone away. That remains to be seen. They really don't have significant data beyond two years, so the idea that there will be no adverse events after two or three years really is an unproven hypothesis.

"If I did informed consent with a patient and they said to me 'What is the proven clinical benefit of this dissolving stent?' I'd have to tell them 'I don't know.'"
-- Simon
Do you see a stent like the Absorb becoming the predominant device used in PCI, replacing drug-eluting stents (DES)?

Simon: It's a niche device. What is its market share in Europe? 5 to 10%? So it's not a workhorse stent. It's not going to be used in the majority of cases. You're not going to use it in small vessels, because we know that's a problem. You can't probably use it now for ostial lesions, because they weren't studied in the pivotal study. So would you use it in a middle-aged man who has disease in his mid-LAD, because you'd say, "Oh. I don't want to cage his LAD because one day I may need to do a bypass." Well, I guess. It's theoretically potentially useful, but patients have this emotional feeling that it's great to have an implant that disappears. But if I did informed consent with the patient, and they said to me, "What is the proven clinical benefit of this disappearing stent?" I'd have to tell them, "I don't know."

Is implantation technique different for the BVS; does it require additional training for the interventional cardiologist?
Kirtane: Yes. The stent, because it's bulkier and has bigger struts, does not have the same degree of tolerance for variations in implantation technique. The newest stents that we have now get to where you need to get them, they expand very well, they perform great.
"It actually makes the procedure more complex"
-- Blankenship
You don't have to have the same assiduous attention to detail when implanting them. That's not going to be the case with the BVS and I think clearly in order to get good or even equal efficacy to the current generation of stents, you need to be more meticulous in your technique than often physicians, especially in the United States, are with their standard implantation technique. Abbott is focused on that and will do extra training because the last thing anybody would want is to have something approved and then have adverse outcomes.
Blankenship: It actually makes the procedure more complex in that you have to do a pre-dilatation, probably a post-dilatation. The BVS is a little more difficult to deploy and you may have to use some kind of imaging to ascertain the true size of it. There's going to be a lot more intravascular ultrasound and OCT being done. So it's going to increase the whole complexity of the deployment. That's not to say it's bad, it's just going to be more complex.
Simon: I'll tell you what my fear is. Obviously I'm not the only one who has this fear. This is a device that's going to have safety videos, deployment videos, that you're going to need to watch, related to determining optimal vessel size: can you interpret an angiogram to know what size stent to put in? Because you can't over dilate it, it'll fracture. You don't want to put it in too small a vessel, because then you have problems. And you need aggressive understanding of lesion preparation, imaging, to make sure you optimally deploy these devices so you don't have problems with stent thrombosis. My only concern is, you get the device into the hands of people who are not high volume technically interventional perfectionists and what you actually see is stent thrombosis rates of 3%. And that's show-stoppers.

"It's a niche device...It's not a workhorse stent. It's not going to be used in the majority of cases."
-- Simon
Simple cases become more complex. And the biggest problem is that, and this is what the FDA fears which is why they're making them do a registry, is interventional cardiologists are notoriously bad at willingness to do indications. So 60% of DES is off-label. So are investigators going to use this in long lesions, in CTOs, in acute MI? And if that's happening, what's going to happen to the results?

BVS was supposed to aid in the reduction of dual antiplatelet therapy (DAPT) after stenting, to avoid potentially fatal stent thrombosis. Has the BVS achieved that?

: No. That's actually a very common misperception by many doctors: that because the stent goes away, we can reduce DAPT. The reality is that it doesn't go away until two to three years out, In addition, because the struts are thicker there's a heightened sensitivity to making sure that folks continue it. So make no mistake. You cannot shorten DAPT with BVS
Simon: The purported benefits of the device with respect to vessel healing was posited as a mechanism to reduce late stent thrombosis, or stent thrombosis in general, and somehow change the need for DAPT. And that obviously is completely wrong. You need more intense DAPT for longer. Stent thrombosis rates are not less. And one could quibble about how much greater they are, but certainly in real world registries, they are at least 2-3%.

Cost has become an important factor in medicine. What is the cost-benefit of the BVS?

Simon: As President of our hospital now, you'd say we're willing to pay for new technology, as long as it brings incremental clinical benefit. You pay $32,000 for a TAVR valve as opposed to $6,000 for a surgical valve, because it has clinical benefit. It allows us to treat patients that we couldn't treat before. It has a huge impact on quality of life. It's a short hospital stay. So you're happy to pay for it. The question here is, let's say you use a $1,200 OCT catheter, you have to use an extra wire, a scoring balloon instead of a pre-dilating balloon, and you use a post-dilating balloon that you only use on occasion and now you use it regularly. And you pay more money for the stent. You've added in conservatively $1,800 more in disposables and you've spent more time and you ask if that's a problem, And you say, "Yes."

"This is a first generation device. They're going to get a lot better. So it's important that we start using it, that we get to know how it works, and encourage the entire field to move ahead"
-- Blankenship

Still, isn't this innovation the most advanced technology around: the newest and brightest?

Simon: The drug-eluting stent world is not standing still, so the criteria for comparison now has to look at other solutions. And that includes everything from Biofreedom to drug-filled stents. Those are devices that have no polymer, short DAPT, smaller, even more deliverable stents, the ability to crimp and a smaller profile. So now you say, "Wow. I get a drug-eluting stent without inflammation, with no polymer, and I can use DAPT for a month if I have to?" That's awesome right?
Kirtane: There are polymer-free and/or bioabsorbable polymer devices that may have the potential to reduce DAPT. And all three of the platforms, Resolute, Xience, and Promus, have been looked at in this way, non-randomized, and not with a lot of patients, but there are ongoing trials. Obviously LEADERS FREE came out with Biofreedom, but even there's a short-DAPT study that's being done with SYNERGY to determine whether shorter durations can be safe.

What about patient preference? As you've said, patients like the idea of having the stent/scaffold disappear.
Blankenship: Iit's going to make the whole issue more complex. We're going to have patients coming in and they're going to be asking, "what about this new kind of stent?" And then we're going to have this whole big explanation of bioresorbable stent, and that's almost a whole separate discussion in itself. How long it's going to take to dissolve, and the pros and cons of it and everything, so when patients come in and ask me, it's going to be a whole other long discussion.

So if the BVS is more difficult to implant, shouldn't be used in small arteries or complex anatomies, and it's more expensive, why did the FDA approve it?
Blankenship: (note: Dr. Blankenship testified before the FDA panel in support of the BVS) I think it should be available now. This is a first generation device. They're going to get a lot better. So it's important that we start using it, that we get to know how it works, and encourage the entire field to move ahead, including getting some competitive brands in and second generation devices and so on. If you don't encourage the technology now, it's just going to delay the evolution of the technology in the United States. Competitors won't find it economically viable to try and get their stents here and it will slow down development of second generation stents and you won't be getting any of the stuff for years. One can argue that it's in the range of the stuff that we're using now and therefore should be available to us.
Simon: If we thought that the Palmaz-Schatz stent that was approved in 1994 was going to be the only stent we were going to ever have, we'd be like, "Oh, my God! Forget about it!" We've had remarkable improvements between Cypher and Taxus and what we have now. So yes, things improve. I try to stress this because I never want to squash technology and innovation. Yes, this is a first generation device. So it has all those limitations. It'll get better. The strut thickness will improve. It'll become more deliverable. But at the end of the day, it is the burden of showing that this device has clinical benefit. And that hasn't been done yet.

Dr. Kirtane reports reports institutional research grants from Abbott, Medtronic and Boston Scientific
Dr. Blankenship reports having served as a site principal investigator for studies funded by approximately eight different companies. He is immediate past-president of the Society for Cardiovascular Angiography and Interventions.
Dr. Simon reports consultant fee, honoraria, or speaker's bureau from HeartFlow and Medtronic

Reported by Burt Cohen, July 24, 2016