Bioresorbable Scaffolds for Below-the-Knee Arterial Disease: A Literature Review of New Developments

Abstract

This review aimed to explore the therapeutic effect of bioabsorbable stents in the inferior genicular artery, from the emergence of absorbable bare metal stents to the latest technology in polymer and anti-proliferative eluting drugs mixed with coated bioresorbable vascular stents (BVSs). Currently, there are conflicting data regarding the safety and effectiveness of BVSs in infrapopliteal artery interventions, especially compared to the current generation of drug-eluting stents (DESs). This review will cover the existing data on BVSs in reconstructing the infrapopliteal arterial blood flow and active clinical trials for future iterations of BVSs. In terms of primary patency rate and target lesion revascularization rate, the available research on the effectiveness of BVSs in reconstructing the infrapopliteal arterial blood flow suggests that a BVS is compatible with current DESs within 3-12 months; long-term data have not yet been reported. The ABSORB BVS is the most studied BVS in cardiovascular disease (CAD). Initially, the ABSORB BVS showed promising results. Managing intricate regions in peripheral artery disorders, such as branching or lengthy lesions, continues to be a formidable undertaking. In contrast to the advanced narrowing of arteries seen in standard permanent stent procedures, bioabsorbable stents have the potential to promote the expansion and beneficial merging of blood channels in the latter stages. Furthermore, incorporating stents and re-establishing the endothelial function can diminish the probability of restenosis or thrombosis. Nevertheless, the extent to which bioabsorbable stents may simultaneously preserve arterial patency and guarantee their structural integrity remains uncertain. The powerful and intricate mechanical stresses exerted by the blood in the superficial femoral artery and popliteal artery can cause negative consequences on any implant inserted into the vessel, regardless of its composition, even metal. Furthermore, incorporating stents is advantageous for treating persistent occlusive lesions since it does not impact later treatments, including corrective bypass operations. Evidence is scarce about the use of bioabsorbable stents in treating infrapopliteal lesions. Utilizing bioabsorbable stents in minor infrapopliteal lesions can successfully maintain the patency of the blood vessel lumen, whereas balloon angioplasty cannot offer this benefit. The primary focus of testing these materials is determining whether bioabsorbable scaffolds can provide adequate radial force in highly calcified elongated lesions. Indeed, using "-limus" medication elution technology in conjunction with bioabsorbable stents has previously offered clinical benefits in treating the popliteal artery, as evidenced by limited trials.BVSs for peripheral arterial disease (PAD) show promise and have the potential to offer a less inflammatory and more vessel-friendly option compared to permanent metallic stents. However, current evidence does not yet allow for a universal recommendation for their use. Thus, ongoing, and future studies, such as those examining the newer generation of bioresorbable scaffolds (BRSs) with improved mechanical properties and resorption profiles, will be crucial in defining the role of BRSs in managing PAD.

Keywords: below-the-knee (BTK) disease; bioresorbable scaffold (BRS); chronic limb-threatening ischemia (CLTI); infrapopliteal artery; patency; thrombosis.

Fig. 1.

Mechanisms of three bioresorbable scaffolds. (Part A) Magnesium alloy stent. (Part B) PLLA stent. (Part C) Tyrocore stent. Part A illustrates the deterioration process of magnesium alloy scaffolds. The picture displays the fundamental reaction equation. Degradation of the magnesium alloy scaffold is initiated within a period of 3–6 months and subsequently transforms into hydroxyapatite, which is absorbed after 9–12 months. Part B illustrates the deterioration of a BVS eluted with everolimus. The release of the drug is often completed within a month, with the stent losing its mechanical reinforcement after approximately a year and a half. Eventually, the stent completely breaks down into water and carbon dioxide through the tricarboxylic acid cycle. Part C illustrates the degradation mechanisms of a Tyrocore BVS, which exhibits accelerated deterioration and experiences mechanical loss within approximately one year. Moreover, the iodinated diphenol, which is a metabolic intermediary, enables the scaffold to be detected and visualized during imaging examinations. AMS, absorbable metal stent; $I_2$DAT, iodinated tyrosine analog; PLLA, poly L-lactic acid; BVS, bioresorbable vascular stent.

Fig. 2.

Risk factors to consider before and following implantation of bioresorbable stents. Before implantation surgery, the critical factors are choosing suitable stents and ensuring proper lesion management. Following surgery, the most crucial aspect is DAPT. However, there is currently a debate regarding the optimal duration of this therapy and whether routine testing of the CYP2C19 gene should be conducted to determine the appropriate use of antiplatelet medications. DAPT, dual anti-platelet therapy.

Fig. 3.

Summary of 1-year pooled results from a meta-analysis of five clinical studies. BRS, bioresorbable scaffold; CI, confidence interval; CD-TLR, clinical-driven target lesion revascularization; PP, proportion.