Current Status of Bioresorbable Scaffolds in the Treatment of Coronary Artery Disease | Ten Points to Remember
- Wiebe J, Nef HM, Hamm CW.
- J Am Coll Cardiol 2014;64:2541-2551.
1. BRS represent a new approach in the interventional treatment of coronary artery disease. Scaffold refers to the temporary nature of BRS (in contrast to the permanent implant of a stent). Although all BRS are referred to as bioresorbable, not all are made from biomaterials.
2. BRS may overcome the following limitations of drug-eluting stents: risk of late and very late stent thrombosis, continued neointimal tissue growth and neoatherosclerosis, malapposition, potential stent fracture, incomplete endothelialization, and vessel caging causing abnormal vasomotion. Due to degradation over time, no foreign body remains in the vessel long-term and, theoretically, this markedly reduces or eliminates the risk for late and very late stent thrombosis.
3. Poly-L-lactic acid (PLLA) is the most common material used for manufacturing BRS. A PLLA-based scaffold has radial strength that is equivalent to that of drug-eluting metallic stents, and such radial support is ensured for approximately 6 months. Complete degradation occurs in 1-3 years.
4. Other than PLLA, the following are also used as materials for manufacturing BRS: magnesium, tyrosine-polycarbonate, and polylactic anhydride. There is variability in time for resorption, which can range from 2 to 36 months, depending on the material.
5. Compared to metallic stents, BRS are better suited for noninvasive imaging, where they do not create imaging artifacts.
6. The first BRS utilized in humans was the Igaki-Tamai stent. Although initial and long-term results were promising, the stent has been discontinued for use in coronary artery disease for the following two reasons: implantation that requires an 8F guiding catheter, and the need for heated contrast dye for balloon inflation (which poses a risk of vessel wall injury).
7. The following two BRS have the Conformite Europeenne (CE) mark for use in coronary artery disease: the Absorb bioresorbable vascular scaffold (BVS, Abbott Vascular, Santa Clara, California) and the DESolve scaffold (Elixir Medical Coroporation, Sunnyvale, California). The former BVS bioresorbable scaffold is the most widely investigated to date. It is made of PLLA, has a strut thickness of 150 micrometers, and elutes the antiproliferative drug everolimus. Full degradation takes up to 3 years.
8. The ABSORB Cohort A and B studies have investigated the use of the BVS. A second-generation BVS (compared to the first-generation BVS, the second-generation devices had redesigned struts associated with increased radial strength, longer radial support, and improved drug transfer) was evaluated in the ABSORB Cohort B study; during 2 years of follow-up, overall major adverse cardiac event (MACE) rate was 9.0%. The DESolve scaffold has been investigated in the multicenter DESolve FiM trial. The advantage of the DESolve scaffold may be a wider range of expansion. A randomized controlled trial comparing BVS and drug-eluting stents is currently ongoing.
9. The authors of the review article opine that diabetics (with a tendency toward diffuse disease and relatively higher risk of in-stent restenosis and thrombosis) may benefit from BRS, compared to drug-eluting stents. The authors caution that ‘BRS implantation should currently be reserved for patients with simple lesions and, until more evidence is available, should always be performed according to the manufacturer’s recommendation.’
10. The following are select limitations associated with BRS: strut thickness (greater than that in conventional stents), mandatory pre-dilation (i.e., direct stenting is not possible), poor deliverability in complex lesions, increased scaffold fracture risk with overdilation, and lack of data or experience to guide the optimal duration of dual antiplatelet therapy following BRS application.
Keywords: Anhydrides, Biocompatible Materials, California, Coronary Artery Disease, Diabetes Mellitus, Drug-Eluting Stents, Lactic Acid, Magnesium, Polycarboxylate Cement, Polymers, Sirolimus, Stents, Thrombosis, Tyrosine
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