A medical breakthrough, bioresorbable scaffolds are designed to repair and restore diseased coronary vessels. They are intended to deliver results similar to drug-eluting stents before being completely resorbed by the body. Despite some limitations, they usher in a new era for interventional cardiology.
A couple of square millimeters is all the space oxygen-rich blood has to push its way through the lumen of a coronary artery.
Plaque lesions along the way do not exactly facilitate the journey and may lead to Coronary Artery Disease (CAD), with its typical symptoms and complications, including angina and myocardial infarction. So ever since researchers and cardiologists have learned about the pathogenesis of CAD, they have been working on materials and techniques to open up lesions and restore blood flow and arterial function.
Following angioplasty-balloons, bare-metal stents (BMS) and drug-eluting stents (DES), the latest addition to the interventional cardiologist’s toolbox is the bioresorbable scaffold, aka bioabsorbable or biodegradable stent, such as Abbott Vascular’s Absorb, or Elixir’s DESolve.
Dissolving Several Months After Implantation
Instead of remaining permanently inside the body, these devices aim at propping up diseased vessels by providing radial strength just as long as it is really necessary, before beginning to gradually degrade several months after implantation. Developers hope this will avoid some of the long-term problems with permanent stents, particularly important for younger patients.
Dr. Petra Guhr, Manager Marketing Communication DACH, at Abbott Vascular, Germany told MedicalExpo:
The dream has always been to find a temporary solution for a temporary problem, giving blood vessels a chance to bounce back to their natural state.
“This is comparable to putting a cast on a broken leg and removing it after the bone is fully healed,” she said. Abbott Vascular has been developing the Absorb Bioresorbable Vascular Scaffold System (BVS) since the early 2000s, winning CE certification in 2010 and a positive review by the U.S. Food and Drug Administration Advisory Committee in 2016.
Absorb BVS consists of bioresorbable scaffold and coating elements, both made of polylactide acids (PLA). Such materials are also used in absorbable surgical sutures and other medical applications, and are the key constituents of Elixir’s DESolve and the ancestor of all bioresorbable scaffolds, the Igaki-Tamai stent, as well. “However, one PLA is not necessarily identical to another. Only the exact composition of the PLA and the design of the scaffold determine its essential properties, such as the speed at which the scaffold dissolves.”
Furthermore, just like Abbott’s industry standard drug-eluting stent, Xience, Absorb BVS releases Everolimus to prevent restenosis, and has an enhanced delivery system to facilitate use. According to Guhr, to date about 125,000 patients have been treated with Absorb worldwide, 13,000 of them in the context of clinical studies.
The Absorb BVS passed the recent ABSORB III non-inferiority trial, using an Xience DES control group. However, although not considered statistically significant, slightly more patients in the Absorb group (7.8%) experienced target lesion failure than in the Xience group (6.1%). This raises the question of whether the new bioresorbable technology might be inferior to established stents after all.
Dr. Samin K. Sharma, Professor of Cardiology at the Mount Sinai Hospital, New York City, has worked in interventional cardiology since the 1980ies and has treated patients as part of the ABSORB III trial. He explained in an interview with MedicalExpo:
I think that this is just work in process. In my opinion, interventionalists have to understand this as a proof of concept – that this is a great technology, it is here to stay, and we need to make it better.
Learning More About This Technology
“I know that a lot of people are sitting on the fence and that there is a borderline enthusiasm on this issue, but I am very enthusiastic. I have used it and I think that will be good for us,” explained Sharma. His current clinical experience with bioresorbable scaffolds includes about 75 patients in the U.S. and India.
We cannot get them in complex lesions yet, because we need to learn how this technology is going to behave in complex lesions. So until we have that, I would say, that we should reserve it for the non-complex, noncalcified lesions.
Might bioresorbable scaffolds replace DES as the gold standard for treating Acute Coronary Syndrome (ACS) in the future? Sharma thinks it will be used as “a specialty item”, particularly because of some limitations, such as when treating lesions around coronary artery bifurcations or in very large vessels.
“Once we improve techniques and maybe get second generations of biodegradable stents, at the peak time my prediction is, that it could take up to 40 percent of the DES-market.”