First-in-man study of a thinner-strut sirolimus-eluting bioresorbable scaffold (FUTURE-I): Three-year clinical and imaging outcomes

Long-term outcomes following bioresorbable vascular scaffolds

INTRODUCTION

The higher scaffold thrombosis rates observed with the first-generation bioresorbable scaffolds (BRSs) compared to conventional drug-eluting stents were likely due in part to bioresorbable polymers having insufficient radial strength, necessitating larger strut profiles. Meta-analysis of the long-term outcomes from the first-generation Absorb bioresorbable vascular scaffold (BVS) showed that this period of excess risk ended at 3 years. Therefore, current attention has been focused on improving early outcomes by increasing the scaffold's tensile strength and reducing strut thickness.

AREAS COVERED

This review summaries the lessons learned from the first-generation BRS. It updates the long-term clinical outcomes of trials evaluating the ABSORB BVS and metallic alloy-based BRS. In addition, it reviews the next-generation BRSs manufactured in Asia.

EXPERT OPINION

Critical areas to improve the performance and safety of biodegradable scaffolds include further development in material science, surface modification, delivery systems, and long-term follow-up studies.

Absorbable metal stents for vascular use in pediatric cardiology: progress and outlook

The past five years have yielded impressive advancements in fully absorbable metal stent technology. The desired ultimate ability for such devices to treat a vascular stenosis without long-term device-related complications or impeding future treatment continues to evoke excitement in clinicians and engineers alike. Nowhere is the need for fully absorbable metal stents greater than in patients experiencing vascular anomalies associated with congenital heart disease (CHD). Perhaps not surprisingly, commercially available absorbable metal stents have been implanted in pediatric cardiology patients with conditions ranging from pulmonary artery and vein stenosis to coarctation of the aorta and conduit/shunt reconstructions. Despite frequent short term procedural success, device performance has missed the mark with the commercially available devices not achieving degradation benchmarks for given applications. In this review we first provide a general overview detailing the theory of absorbable metal stents, and then review recent clinical use in CHD patients since the release of current-generation absorbable metal stents around 2019. We also discuss the challenges and our center's experience associated with the use of absorbable metal stents in this pediatric population. Lastly, we present potential directions for future engineering endeavors to mitigate existing challenges.

Senescent endothelial cells' response to the degradation of bioresorbable scaffold induces intimal dysfunction accelerating in-stent restenosis

Atherosclerotic cardiovascular disease is a typical age-related disease accompanied by stiffening arteries. We aimed to elucidate the influence of aged arteries on in-stent restenosis (ISR) after the implantation of bioresorbable scaffolds (BRS). Histology and optical coherence tomography showed increased lumen loss and ISR in the aged abdominal aorta of Sprague-Dawley rats, with apparent scaffold degradation and deformation, which induce lower wall shear stress (WSS). This was also the case at the distal end of BRS, where the scaffolds degraded faster, and significant lumen loss was followed by a lower WSS. In addition, early thrombosis, inflammation, and delayed re-endothelialization were presented in the aged arteries. Degradation of BRS causes more senescent cells in the aged vasculature, increasing endothelial cell dysfunction and the risk of ISR. Thus, profoundly understanding the mechanism between BRS and senescent cells may give a meaningful guide for the age-related scaffold design. STATEMENT OF SIGNIFICANCE: The degradation of bioresorbable scaffolds aggravates senescent endothelial cells and a much lower wall shear stress areas in the aged vasculature, lead to intimal dysfunction and increasing in-stent restenosis risk. Early thrombosis and inflammation, as well as delayed re-endothelialization, are presented in the aged vasculature after bioresorbable scaffolds implantation. Age stratification during the clinical evaluation and senolytics in the design of new bioresorbable scaffolds should be considered, especially for old patients.

Nanoparticles-reinforced poly-l-lactic acid composite materials as bioresorbable scaffold candidates for coronary stents: Insights from mechanical and finite element analysis

Current generation of bioresorbable coronary scaffolds (BRS) posed thrombogenicity and deployment issues owing to its thick struts and overall profile. To this end, we hypothesize that the use of nanocomposite materials is able to provide improved material properties and sufficient radial strength for the intended application even at reduced strut thickness. The nanocomposite formulations of tantalum dioxide (Ta₂O₅), L-lactide functionalized (LA)-Ta₂O₅, hydroxyapatite (HA) and LA-HA with poly-l-lactic acid (PLLA) were evaluated in this study. Results showed that tensile modulus and strength were enhanced with non-functionalized nanofillers up until 15 wt% loading, whereas ductility was compromised. On the other hand, functionalized nanofillers/PLLA exhibited improved nanofiller dispersion which resulted higher tensile modulus, strength, and ductility. Selected nanocomposite formulations were evaluated using finite element analysis (FEA) of a stent with varying strut thickness (80, 100 and 150 μm). FEA data has shown that nanocomposite BRS with thinner struts (80-100 μm) made with 15 wt% LA-Ta₂O₅/PLLA and 10 wt% LA-HA/PLLA have increased radial strength, stiffness and reduced recoil compared to PLLA BRS at 150 μm. The reduced strut thickness can potentially mitigate issues such as scaffold thrombosis and promote re-endothelialisation of the vessel.

Thinner Strut Sirolimus-Eluting BRS Versus EES in Patients With Coronary Artery Disease: FUTURE-II Trial

OBJECTIVES

The aim of the present study was to evaluate the safety and efficacy of thinner strut Firesorb (100/125 μm) sirolimus-eluting bioresorbable scaffolds (BRS) versus cobalt-chromium everolimus-eluting stents (CoCr-EES) in patients with coronary artery disease.

BACKGROUND

First-generation thicker strut BRS were associated with unexpected device-related adverse outcomes at long-term follow-up.

METHODS

Eligible patients with 1 or 2 de novo noncomplex coronary lesions were randomized to the Firesorb BRS group or CoCr-EES group in a 1:1 ratio. The primary endpoint was 1-year angiographic in-segment late loss (LL), powered for noninferiority testing. The key secondary endpoint was the 1-year proportion of covered struts assessed on optical coherence tomography, powered for noninferiority and subsequent superiority testing.

RESULTS

A total of 433 participants from 28 Chinese centers were randomized to the Firesorb BRS group (n = 215) or CoCr-EES group (n = 218). Patient-level 1-year in-segment LL was 0.17 ± 0.27 mm in the Firesorb BRS group and 0.18 ± 0.37 mm in the CoCr-EES group (difference -0.01 mm; 95% confidence interval [CI]: -0.07 to 0.06; p_{noninferiority} < 0.0001) in the intention-to-treat population and was 0.17 ± 0.27 mm in the Firesorb BRS group and 0.19 ± 0.37 mm in the CoCr-EES group (difference -0.005 mm; 95% CI: -0.07 to 0.06; p_{noninferiority} < 0.0001) in the per-protocol set. The proportion of covered struts was 99.3% in the Firesorb BRS group and 98.8% in the CoCr-EES group (difference 0.8%; 95% CI: -0.5% to 2.1%; p_{noninferiority} < 0.0001; p_superiority = 0.21). One-year clinical outcomes were similar between groups.

CONCLUSIONS

The thinner strut Firesorb BRS was noninferior to the CoCr-EES for the primary endpoint of 1-year angiographic in-segment LL and the key secondary endpoint of 1-year proportion of covered struts by optical coherence tomography. (A Trial of Firesorb in Patients With Coronary Artery Disease: FUTURE-II [FUTURE-II]; NCT02890160).

Bioresorbable Scaffolds: Contemporary Status and Future Directions

Percutaneous coronary intervention, which is safe, effective, and timely, has become an important treatment for coronary artery diseases and has been widely used in clinical practice. However, there are still some problems that urgently need to be solved. Permanent vessel caging through metallic implants not only prevents the process of positive vessel remodeling and the restoration of vascular physiology but also makes the future revascularization of target vessels more difficult. Bioresorbable scaffolds (BRSs) have been developed as a potential solution to avoid the above adverse reactions caused by permanent metallic devices. BRSs provide temporary support to the vessel wall in the short term and then gradually degrade over time to restore the natural state of coronary arteries. Nonetheless, long-term follow-up of large-scale trials has drawn considerable attention to the safety of BRSs, and the significantly increased risk of late scaffold thrombosis (ScT) limits its clinical application. In this review, we summarize the current status and clinical experiences of BRSs to understand the application prospects and limitations of these devices. In addition, we focus on ScT after implantation, as it is currently the primary drawback of BRS. We also analyze the causes of ScT and discuss improvements required to overcome this serious drawback and to move the field forward.

In vivo degradation and endothelialization of an iron bioresorbable scaffold

Detection of in vivo biodegradation is critical for development of next-generation medical devices such as bioresorbable stents or scaffolds (BRSs). In particular, it is urgent to establish a nondestructive approach to examine in vivo degradation of a new-generation coronary stent for interventional treatment based on mammal experiments; otherwise it is not available to semi-quantitatively monitor biodegradation in any clinical trial. Herein, we put forward a semi-quantitative approach to measure degradation of a sirolimus-eluting iron bioresorbable scaffold (IBS) based on optical coherence tomography (OCT) images; this approach was confirmed to be consistent with the present weight-loss measurements, which is, however, a destructive approach. The IBS was fabricated by a metal-polymer composite technique with a polylactide coating on an iron stent. The efficacy as a coronary stent of this new bioresorbable scaffold was compared with that of a permanent metal stent with the name of trade mark Xience, which has been widely used in clinic. The endothelial coverage on IBS was found to be greater than on Xience after implantation in a rabbit model; and our well-designed ultrathin stent exhibited less individual variation. We further examined degradation of the IBSs in both minipig coronary artery and rabbit abdominal aorta models. The present result indicated much faster iron degradation of IBS in the rabbit model than in the porcine model. The semi-quantitative approach to detect biodegradation of IBS and the finding of the species difference might be stimulating for fundamental investigation of biodegradable implants and clinical translation of the next-generation coronary stents.

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A semi-quantitative OCT method was suggested to evaluate in vivo biodegradation of an iron based coronary stent IBS in a nondestructive manner.

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The in vivo biodegradation of IBS exhibited dependence on animal species.

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The endothelial coverage on the biodegradable stent IBS was better than on the commercialized nonbiodegradable stent Xience in rabbits.

Three-year outcomes of bioresorbable vascular scaffolds versus second-generation drug-eluting stents: Meta-analysis of randomized trials

BACKGROUND

Bioresorbable vascular scaffolds (BVS) completely resorb within 3 years after placement into the coronary artery. The safety and effectiveness of bioabsorbable scaffolds are of critical importance during this 3-year period.

OBJECTIVE

We performed a meta-analysis to compare the safety and efficacy of BVS and second-generation drug-eluting stents (DES) at 3 years after implantation.

METHODS

Published randomized trials comparing BVS to second-generation DES for the treatment of coronary artery disease were identified within PubMed, EMBASE, Cochrane Library, Web of Science, and relevant Web sites with publication dates through June 2019. The primary efficacy endpoint was target lesion failure. The primary safety endpoint was definite/probable stent/scaffold thrombosis. Secondary outcomes were cardiac death, target vessel myocardial infarction, ischemia-driven target lesion revascularization, and a patient-oriented composite end point.

RESULTS

Six randomized controlled trials, with a total of 5,412 patients (BVS n = 3,177; DES n = 2,235), were included. At 3 years, BVS was associated with higher rates of target lesion failure (OR = 1.33, 95%CI: 1.10-1.60, P = 0.003) and definite/probable stent/scaffold thrombosis (OR = 3.75, 95% CI: 2.22-6.35, P < .00001)compared with DES. The incidence of target vessel myocardial infarction (OR = 1.68, 95% CI: 1.30-2.17, P < .0001), ischemia-driven target lesion revascularization (OR = 1.46, 95% CI: 1.14-1.86, P = .003), and the patient-oriented composite end point(OR = 1.20, 95% CI: 1.04-1.39, P = .01) were higher for those treated with BVS compared with DES. However, there was no significant difference in risk of cardiac death (OR = 0.94, 95%CI: 0.61-1.45, P = .79) between treatment groups.

CONCLUSIONS

At the 3-year follow-up, BVS was inferior to second-generation DES in both safety and efficacy.