Version July 2025
INTRODUCTION —
Most commercially available drug-eluting intracoronary stents (DES) consist of a metallic scaffold, a polymer coating (which may be durable or bioresorbable), and an antirestenotic drug that is mixed within the polymer and released over a period of weeks to months after implantation (table 1). The use of current-generation DES is associated with low rates of restenosis, target lesion revascularization, and stent thrombosis compared with early-generation DES or bare metal stents. However, major adverse cardiovascular events such as restenosis or stent thrombosis continue at a low rate after one year with approved, commercially available, current-generation stents. (See "Intracoronary stent restenosis" and "Coronary artery stent thrombosis: Incidence and risk factors".)
Ongoing research aims to lower the risk of these stent-related adverse cardiovascular outcomes by manipulating one or more components of the stent: the scaffold, the polymer, or the drug.
This topic will focus on efforts to further lower the rate of adverse events by eliminating the metallic stent. Ultra-thin stents are discussed separately. (See "Intracoronary stents: Stent types", section on 'Ultra-thin-strut bioresorbable drug-eluting stents'.)
Other relevant topics include:
●(See "Percutaneous coronary intervention with intracoronary stents: Overview".)
●(See "Intracoronary stents: Stent types".)
ADVANTAGES AND DISADVANTAGES OF CURRENT-GENERATION SCAFFOLDS —
Current-generation drug-eluting intracoronary stents (DES) contain a metal backbone that almost entirely eliminates acute or subacute recoil of the stented coronary artery compared with balloon angioplasty. In addition, they decrease the likelihood and extent of late lumen loss and restenosis of the treated segment. As restenosis is uncommonly seen 9 to 12 months after the procedure, the need for stent scaffolding after this period is likely limited. (See "Percutaneous coronary intervention with intracoronary stents: Overview", section on 'Benefits of stenting'.)
Potential long-term adverse consequences of the metallic stent include permanent side branch occlusion, restriction of noninvasive imaging of coronary arteries with multislice computed tomography and magnetic resonance imaging, and interference with the ability to place a bypass graft at the stented site.
The development of some late adverse events after placement of permanent metallic stents, such as restenosis or stent thrombosis, has been attributed to persistent inflammation, impaired vasomotion, ongoing tissue growth within the stent frame, and neoatherosclerosis [1].
RATIONALE FOR BIORESORBABLE SCAFFOLD STENTS —
Fully biodegradable stents, which are also referred to as bioresorbable stents or bioresorbable scaffolds, have the potential to overcome some of the disadvantages of metal stents. With these devices, the scaffold is in place only long enough to protect against subacute closure, wall recoil, and early restenosis. Most of them provide vascular scaffold support for up to one year, after which time they will have completely resorbed. The use of these devices is hoped to improve outcomes in patients who need repeat percutaneous coronary intervention or coronary artery bypass graft surgery.
The disadvantages of these devices are that first-generation scaffolds had thicker struts compared with current-generation stents, were more difficult to implant than metal alloy stents, and can fracture with overdeployment from balloon dilation. In addition, the radio-opacity was poor, so visualization of deployed scaffold was difficult. Other potential limitations have been cited [2].
BIORESORBABLE SCAFFOLDS —
A bioresorbable vascular stent (the Absorb stent) was approved for use by the US Food and Drug Administration in 2016, but uptake was low in the United States [3]. Sale was halted worldwide by the manufacturer in September 2017 due to an increase in observed late myocardial infarction (MI) and scaffold thrombosis. Other bioresorbable scaffolds are under evaluation. In the United States, there are no approved bioresorbable vascular scaffolds. The European Medicines use of Certificate of Conformity (CE marking) bioresorbable scaffold devices is discouraged outside of clinical trials [4].
Early trials using a variety of scaffolding materials provided the basis for the current generation of bioresorbable scaffolds under investigation [5-11].
Poly(L)-lactic acid scaffold — There is no evidence that poly(L)-lactic acid (PLLA) scaffolds are superior to current-generation metallic stents. The Absorb and NeoVas stents are representative of this group.
The Absorb bioresorbable vascular scaffold (BVS) consists of a 150-mcm-thick bioresorbable PLLA scaffold with a 7-mcm-thick bioresorbable PLLA coating polymer, and eluted everolimus.
Randomized trials have compared the efficacy and safety of the Absorb BVS with everolimus-eluting metallic stents (EES): ABSORB II [12], EVERBIO II [13], ABSORB Japan [14], ABSORB III [1], ABSORB China [15], TROFI II [16], and AIDA [17]. A 2017 meta-analysis of these randomized trials (n = 5583) concluded that the risks of target lesion failure and stent thrombosis were higher with the Absorb BRS than with EES at a median follow-up of two years [18]. Other meta-analyses of these studies came to similar conclusions [19-23]. The final analysis of the ABSORB trial found that the period of excess risk with the Absorb BVS ended at three years, when bioresorption was complete [24]; between three and five years, the rates of target lesion failure and stent thrombosis were comparable with BVS and EES.
NeoVas is a second PLLA stent that elutes sirolimus from a poly(D,L-lactide) coating. The total strut thickness is 170 mcm. In vivo, porcine studies have demonstrated that the PLLA polymer is completely resorbed in approximately 36 months. In a study of 560 patients with single de novo coronary artery lesions, individuals were randomly assigned to NeoVas or to a cobalt chromium EES [25]. One-year in-segment lumen loss with NeoVas and cobalt chromium EES was similar (0.14±0.36 versus 0.11±0.34 mm, respectively; difference 0.03 mm; upper one-sided 97.5% CI 0.09 mm). Clinical outcomes at one year were similar in the two groups, as were the rates of recurrent angina (27.9 versus 32.1 percent).
Magnesium alloy scaffold — Resorbable metallic scaffolds have been developed. Metals have included magnesium and iron [26,27].
The BIOSOLVE-II study treated 123 lesions in 123 patients (with stable or unstable angina or documented silent ischemia) with the second-generation sirolimus-eluting absorbable magnesium alloy scaffold (DREAMS 2G) [26]. At six months, the primary endpoint of mean in-segment late lumen loss was 0.27 mm. Angiographically detectable vasomotion was documented in 80 percent of 20 patients who were evaluated. The subsequent BIOMAG-I study treated 116 patients with a third-generation sirolimus-eluting magnesium scaffold (DREAMS 3G) [28]. At 12 months, in-scaffold late lumen loss was 0.24 mm and three target lesion failures occurred (2.6 percent). There are no clinical trial data comparing magnesium alloy scaffolds with drug-eluting stents.
Polycarbonate copolymer bioresorbable scaffold — The Fantom sirolimus-eluting bioresorbable scaffold uses a proprietary iodinated, polycarbonate copolymer of tyrosine analogs that is radiopaque, with thin struts (125 mcm). In a single-arm study of 117 patients, mean six-month in-stent late lumen loss was 0.25±0.40 mm (n = 100) [29]. The Fantom II trial prospectively enrolled 240 patients with stable or unstable angina and a single de novo coronary stenosis with reference vessel diameter 2.5 to 3.5 mm diameter and lesion length ≤20 mm. The mean in-stent late lumen loss at nine months was 0.33±0.36 mm, and in-segment binary restenosis occurred in 7.6 percent of patients. Major adverse cardiac events and target lesion failure through 12 months occurred in 4.2 percent of patients; scaffold thrombosis developed in only one patient (0.4 percent) [30].
The DynamX Bioadaptor is a hybrid (ie, metal with bioresorbable polymer coating) device designed to reduce late device-related events. In the INFINITY-SWEDEHEART trial, in which 2399 patients were randomly assigned to the bioadaptor or a contemporary drug-eluting stent, target lesion failure was similar between the groups [31]. However, in a prespecified landmark analysis of outcomes between 6 and 12 months, target lesion failure was lower in those who received a bioadaptor (hazard ratio [HR] 0.19, 95% CI 0.06-0.65).
CLINICAL USE —
There are no bioresorbable scaffolds approved for use in the United States. In Europe, there are a few bioresorbable scaffolds with CE marking, but European guidelines recommend their use only in clinical trials.
Successful devices from regulatory and clinical standpoints will need to demonstrate an absorption timeframe that allows for a similar or shorter duration of dual antiplatelet therapy than available metallic drug-eluting stents. Studies must also confirm the anticipated benefit of improved long-term vessel healing (using intracoronary imaging and vasomotion responses) without an increase in adverse events of restenosis or scaffold thrombosis during the resorption period. The concept remains an attractive one, but adequately sized and well-designed clinical trials are required.
SUMMARY AND RECOMMENDATIONS
●Advantages and disadvantages – Potential long-term adverse consequences of current-generation metallic drug-eluting stents (DES) include permanent side branch occlusion, restriction of noninvasive imaging of coronary arteries, and the interference with the ability to place a bypass graft at the stented site. (See 'Advantages and disadvantages of current-generation scaffolds' above.)
●Rationale – Fully biodegradable stents, which are also referred to as bioresorbable stents or bioresorbable scaffolds, are being tested in clinical trials in an attempt to overcome some of the disadvantages of current-generation DES that have a metallic backbone. (See 'Rationale for bioresorbable scaffold stents' above.)
●Clinical use – There are no bioresorbable scaffolds approved for use in the United States. In Europe, there are a few bioresorbable scaffolds with CE marking, but European guidelines recommend their use only in clinical trials. (See 'Bioresorbable scaffolds' above and 'Clinical use' above.)
