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FDA approves first fully bioresorbable stent for treatment of CAD
The FDA and Abbott announced that the agency has approved the first fully bioresorbable stent indicated for patients with CAD.
The device (Absorb GT1 Bioresorbable Vascular Scaffold System, Abbott Vascular) limits the growth of scar tissue by releasing everolimus into the body and is gradually absorbed by the body over approximately 3 years, leaving behind four small platinum markers embedded in the arterial walls to help identify its prior location, according to press releases from the company and the agency.
“The FDA’s approval of the Absorb GT1 BVS offers a new treatment option for individuals who are candidates for [PCI], but would prefer an absorbable device rather than a permanent metallic coronary stent,” said Bram Zuckerman, MD, director of the division of cardiovascular devices at the FDA’s Center for Devices and Radiological Health.
Approval was based on the ABSORB III trial of 2,008 patients that compared short-term and mid-term outcomes of the bioresorbable vascular scaffold (BVS) to a metallic stent (Xience, Abbott Vascular). The BVS had similar rates of cardiac adverse events compared with the metallic stent (7.8% vs. 6.1%, respectively). The rate of device thrombosis at 1 year was slightly higher for the BVS (1.54% vs. 0.74%).
According to the FDA release, possible adverse events related to the use of the BVS include allergic reaction to poly(L-lactide), poly(D, L-lactide), platinum or the drug everolimus, as well as infection or internal bleeding.
Abbott is planning to first offer the device to centers that participated in the clinical trial program and eventually to all U.S. hospitals, according to the company release.
Gregg W. Stone, MD, FACC, FSCAI, director, cardiovascular research and education, Center for Interventional Vascular Therapy, NewYork-Presbyterian Hospital/Columbia University Medical Center, and chairman of the ABSORB clinical trial program, said in Abbott’s release that “No metal means the treated artery can pulse and flex naturally as demands on the heart change with everyday activities. No metal may also reduce the potential of future blockages that occur with permanent metallic stents, and allows easier access to other treatment options should they prove necessary in the patient’s future.”
Reference: Zuckerman is an employee of the FDA. Stone reports receiving consulting fees from Boston Scientific, Cardiovascular Systems Inc., Eli Lilly/Daiichi Sankyo, InfraReDx, InspireMD, Matrizyme, Miracor, Osprey, Reva, TherOx, Vascular Dynamics and Velomedix; and holding equity interest in Biostar, Cagent, Caliber, Guided Delivery Systems, MedFocus, Micardia, Qool Therapeutics and Vascular Nanotransfer.
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I cannot emphasize enough the importance of appropriate patient and lesion selection, and how important it will be to revisit good fundamental PCI technique when implanting this device. To my eye, this first-generation device has less tolerance to variability in technique than other contemporary metallic drug-eluting stents, which is why optimization of stenting technique is so critical.
There are definitely patients for whom it will be useful (eg, younger patients with less complex lesions who do not want a permanent implant). I do think that this will be a minority of our patients, though, given the excellent performance of the current-generation of metallic DES. At least based upon experience outside the United States, the current generation of metallic DES do have advantages (eg, in deliverability due to strut thickness) which are likely to be more manifest in more complex lesion subsets. Remember also that while the potential advantage of the BVS may present a compelling story, this story is as yet unproven, and we await the longer-term results of ABSORB II, III and IV to provide these data.
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The approval of a fully bioresorbable stent marks a very important milestone in interventional cardiology. A device that delivers the functionality of a stent and leaves the vessel very close to its native condition, with natural reactivity and function, opens up a myriad of possibilities and options for cardiac patients to benefit from. This marks the beginning of a new era of "smart devices," pushing the envelope in technologic advancement.
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This approval is important for at least two reasons. No. 1, it gives physicians and patients another treatment option. No. 2, it gives a boost to the field of research in this area. If the FDA had rejected this, it would have put a damper on further research. It’s very expensive to do device-related research.
We know that for properly selected patients — with relatively focal lesions in medium to large vessels — with good technique, the results are more or less the same as second-generation DES, at least out to 1 year. What we don’t really know is how well the BVS performs in truly complex patients and lesions, and the long-term results, which we hope are superior. I think it will be used in patients who meet the above criteria, but there will probably be more of an impetus to use it in the truly young patient, where you don’t want to have a residual metallic stent in place for years at a time.
One thing we learned, principally from the ABSORB III study, was don’t use this device in small vessels. That is its principal limitation. Another is that we don’t know how well it performs in complex lesions. The Europeans have explored this area somewhat, but not in the form of randomized trials. Until we have further data, it’s hard to argue that it should be used in patients that are outside the realm of eligibility criteria for ABSORB III.
Using this device does require some change in technique. It is bulkier than current second-generation stents. It’s essentially the same size as the first-generation sirolimus-eluting stent (Cypher, Cordis). Most of us have found that because it’s plastic, it’s a little more deliverable than Cypher, but it’s certainly not as deliverable as current second-generation stents. You have to do a little extra work. You must make sure the treatment site is adequately prepared with good pre-dilatation and expansion. You need to make sure there is no heavy calcium or anything that might obstruct the delivery of the scaffold to the site. Once the device is delivered, the data suggest the site should be post-dilated at reasonably high pressure. The scaffold dimensions may predispose it to thrombosis a little more than a second-generation DES. We need to be more meticulous about the delivery of this device than that of a second-generation DES.
We are getting much-needed long-term follow-up, as 5- and 7-year follow-up is planned for ABSORB III and ABSORB IV. We need better data in complex patients. While we have some data from registries, I am always skeptical of data coming out of an environment that is not terribly well-controlled when there is no randomized comparison against the gold standard. We also need to resolve the issue of duration of dual antiplatelet therapy. The protocols have required it between 6 months and 12 months, which is probably reasonable, but we don’t know the answer.