The STENTYS self-apposing stent technology in coronary artery disease: literature review and future directions

Finite element analysis of the mechanical performance of self-expanding endovascular stents made with new nickel-free superelastic β-titanium alloys

New Ni-free superelastic β-titanium alloys from the Ti-Zr-Nb-Sn system have been designed in this study to replace the NiTi alloy currently used for self-expanding endovascular stents. The simulation results, carried out by finite element analysis (FEA) on two β-type Ti-Zr-Nb-Sn alloys using a commonly used superelastic constitutive model, were in good agreement with the experimental uniaxial tension data. An ad-hoc self-expanding coronary stent was specifically designed for the present study. To assess the mechanical performance of the endovascular stents, a FEA framework of the stent deployed in the arterial system was established, and a simply cyclic bending loading was proposed. Six comparative simulations of three superelastic materials (including NiTi for comparison) and two arterial configurations were successfully conducted. The mechanical behaviours of the stents were analysed through stress localization, the increase in artery diameter, contact results, and distributions of mean and alternating strain. The simulation results show that the Ti-22Zr-11Nb-2Sn (at. %) alloy composition for the stent produces the largest contact area (9.92 mm2) and radial contact force (49.5 mN) on the inner surface of the plaque and a higher increase in the stenotic artery diameter (70 %) after three vascular bending cycles. Furthermore, the Ti-22Zr-11Nb-2Sn stent exhibited sufficient crimping capacity and reliable mechanical performance during deployment and cyclic bending, which could make it a suitable choice for self-expanding coronary stents. In this work, the implementation of finite element analysis has thus made it possible to propose a solid basis for the mechanical evaluation of these stents fabricated in new Ni-free superelastic β-Ti alloys.

STENTYS coronary system: current status and future direction

Stentys self-apposing stent was designed to face complex lesions in the precincts of percutaneous coronary interventions. Nitinol platform and disconnectable struts were designed to provide a complete apposition on the vessel wall in challenging lesions such as significant tapering, primary angioplasty in ST segment elevation myocardial infarction and bifurcation. Stentys X-position S is a sirolimus eluting stent with a novel delivery system aiming to improve positioning. Clinical trials showed good results in terms of procedural success rate, clinical outcome and short-term strut apposition. Nevertheless, Stentys stent did not show superiority over the conventional balloon-expandable stents in the clinical outcomes. Authors underlined the importance of a learning curve and an adequate training period to get familiar with the device's features. Future trials in an all-comer population using the novel X-Position S stent will confirm the preliminary findings and strengthen evidence in clinical practice.

Focus on STENTYS® Xposition S Self-Apposing® stent: a review of available literature

Percutaneous coronary interventions are the primary revascularization strategy for the vast majority of patients with coronary artery disease. Nevertheless, challenging settings still limit optimal results, especially in case of significant tapering, bifurcations or primary angioplasty in ST-segment elevation myocardial infarction. Stentys^® Self-Apposing^® stent was designed to improve strut apposition to the vessel wall and to adapt to difficult targets. The Xposition S is a sirolimus-eluting stent with a novel delivery system, to improve accurate positioning. Several studies compared the device with traditional balloon-expandable stents, showing better results in terms of malapposition reduction and a noninferiority in relation to procedural outcomes. Available data show good clinical results, but a direct comparison with balloon-expandable stents from large randomized trials is still lacking. Thus, the Stentys Xposition S can be an alternative to traditional stents in dedicated scenarios, but strong evidence from large randomized trials is needed to derive stronger recommendations.

Testing bioresorbable stent feasibility in a rat aneurysm model

Background

Advances in stent-assisted coiling have incrementally expanded endovascular treatment options for complex cerebral aneurysms. After successful coil consolidation and aneurysm occlusion, endovascular scaffolds are no longer needed. Thus, bioresorbable stents that disappear after aneurysm healing could avoid future risks of in-stent thrombosis and the need for lifelong antiplatelet therapy.

Objective

To assess the applicability and compatibility of a bioresorbable magnesium- alloy stent (brMAS) for assisted coiling.

Methods

Saccular sidewall aneurysms were created in 84 male Wistar rats and treated with brMAS alone, brMAS + aspirin, or brMAS + coils + aspirin. Control groups included no treatment (natural course), solely aspirin treatment, or conventional cobalt–chromium stent + coils + aspirin treatment. After 1 and 4 weeks, aneurysm specimens were harvested and macroscopically, histologically, and molecularly examined for healing, parent artery perfusion status, and inflammatory reactions. Stent degradation was monitored for up to 6 months with micro-computed and optical coherence tomography.

Results

Aneurysms treated with brMAS showed advanced healing, neointima formation, and subsequent stent degradation. Additional administration of aspirin sustained aneurysm healing while reducing stent-induced intraluminal and periadventitial inflammatory responses. No negative interaction was detected between platinum coils and brMAS. Progressive brMAS degradation was confirmed.

Conclusions

brMAS induced appropriate healing in this sidewall aneurysm model. The concept of using bioresorbable materials to promote complete aneurysm healing and subsequent stent degradation seems promising. These results should encourage further device refinements and clinical evaluation of this treatment strategy for cerebrovascular aneurysms.