Are there stents that dissolve over time to act like angioplasty?

Bioresorbable Vascular Scaffolds: Dissolvable Stents for Coronary Intervention

Yes, bioresorbable vascular scaffolds (BVS) are dissolvable stents that provide temporary mechanical support after angioplasty and then completely resorb over time, theoretically combining the benefits of angioplasty with temporary scaffolding to prevent vessel recoil. 1, 2

How Bioresorbable Scaffolds Work

Bioresorbable scaffolds operate through three distinct functional phases that address different physiologic requirements over time 3:

• Revascularization phase: The scaffold provides immediate mechanical support to the dilated vessel segment, preventing elastic recoil and negative remodeling similar to metallic stents 1, 3
• Restoration phase: The scaffold maintains vessel patency while allowing favorable arterial remodeling and restoration of normal vascular physiology 1, 4
• Resorption phase: The scaffold undergoes controlled degradation through hydrolytic breakdown, typically over 2-3 years, leaving no permanent foreign material 3, 4

Materials and Available Devices

The most commonly used materials are poly(L-lactide) (PLLA) polymers and magnesium alloys 2:

• Three devices are currently CE marked for clinical use in Europe, though clinical adoption has been limited 2
• Twenty-four companies are developing coronary bioresorbable devices, indicating ongoing innovation in this field 2
• Most designs use aliphatic polyesters that undergo progressive degradation in molecular weight, strength, and mass consistent with the three performance phases 3

Critical Safety Concerns: Scaffold Thrombosis

The primary limitation preventing widespread BVS adoption is a significantly increased risk of late scaffold thrombosis (ScT), which has emerged as a serious safety concern in long-term follow-up studies. 5, 4

The European Society of Cardiology guidelines note specific concerns 5:

• Recent clinical trials showed a three- to four-fold increase in scaffold thrombosis at median follow-up of approximately 700 days compared to metallic drug-eluting stents 5
• A second period of thrombotic risk occurs between one and three years after implantation, potentially related to scaffold dismantling during bioresorption 5
• Premature discontinuation of dual antiplatelet therapy (DAPT) before 18 months appears to increase scaffold thrombosis risk 5

Current Clinical Recommendations

Based on the safety concerns, the European Society of Cardiology Task Force recommends 5:

• Prolongation of DAPT beyond 12 months (Class IIa recommendation, Level of Evidence C) for patients receiving bioresorbable scaffolds, ideally for 2-3 years to maintain high platelet inhibition during scaffold resorption 5
• This contrasts with metallic drug-eluting stents, which typically require only 6-12 months of DAPT 6

Theoretical Advantages vs. Clinical Reality

While bioresorbable scaffolds were designed to overcome metallic stent limitations, the theoretical advantages have yet to be demonstrated in clinical practice 1:

Intended benefits 1, 2, 4:

• Avoidance of permanent vessel caging that impairs arterial physiology
• Prevention of late complications including inflammation, neoatherosclerosis, and chronic in-stent restenosis
• Allowance for future surgical revascularization without metallic interference
• Restoration of normal vasomotion and positive vessel remodeling

Clinical reality 4:

• Significantly increased late scaffold thrombosis rates limit clinical application
• Long-term safety concerns have overshadowed potential benefits
• The technology remains in its infancy despite over a decade since first implantation 7

Application Beyond Coronary Arteries

Bioresorbable scaffolds have been studied in peripheral vascular disease, particularly the superficial femoral artery 7:

• Early experiences suggest antiproliferative drug elution may be necessary to obtain clinically acceptable results 7
• The importance of material selection, device design, and absorption duration has become apparent through these studies 7
• Results of larger studies with longer follow-up are needed to define the precise role in peripheral applications 7

Common Pitfalls to Avoid

• Do not discontinue DAPT prematurely in patients with bioresorbable scaffolds; maintain therapy for at least 18 months and ideally 2-3 years to prevent catastrophic late scaffold thrombosis 5
• Do not assume bioresorbable scaffolds are equivalent to metallic drug-eluting stents in safety profile; current evidence shows increased thrombotic risk 5, 4
• Do not use bioresorbable scaffolds as routine first-line therapy; metallic drug-eluting stents remain the standard of care with superior long-term safety data 5