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.

The unpredictable resorption of bioresorbable scaffolds-A tale of two ABSORBs

Bioresorbable stents represent a revolutionary treatment for coronary artery disease. Such a device offers the prospect for complete naturalization of artery lumen after strut resorption and restoration of vasomotion while curtailing the duration of dual anti-platelet therapy. The prototype bioresorbable scaffold (BRS-ABSORB GT1) demonstrated good feasibility and safety in the initial studies compared to metallic drug eluting stent but later fell out of favor due to multiple report of stent thrombosis and target lesion failure. Unpredictable resorption of struts turned out to be one of the "Achilles heel" of the BRS and stent strut were still visible in vessel on optical coherence tomography (OCT) at 3 years. We report a case of differential resorption of two ABSORB BRS implanted simultaneously in the same patient by the same operator. Follow up coronary angiogram revealed only minimal plaques on right coronary artery (RCA) and left anterior descending artery (LAD). The BRS were identified on cine-angiogram by their radio-opaque markers at both ends. The OCT run in LAD artery revealed "ghost remnants" of BRS struts in LAD, whereas the RCA BRS had completely healed with minimal "ghost" struts. The ghost remnants of BRS resembled the original "Check box" appearance on OCT during the index implantation.

Two-Year Outcomes for Patients with Non-ST-Elevation Acute Coronary Syndrome Treated with Magmaris and Absorb Bioresorbable Scaffolds in Large-Vessel Lesions

BACKGROUND

The acute coronary syndrome (ACS) continues to be a fundamental indication for revascularization by percutaneous coronary intervention (PCI). Drug-eluting stent (DES) implantation remains a part of contemporary practice but permanent caging of the vascular structure with the metallic stent structure may increase the rate of device-related adverse clinical events. As an alternative to classic metallic DESs, the bioresorbable scaffolds (BRSs) have emerged as a temporary vascular support technology. We evaluated the mid-term outcomes of two generations of bioresorbable scaffolds-Absorb (Abbott-Vascular, Chicago, IL, USA) and Magmaris (Biotronik, Germany)-in patients with non-ST-elevation ACS.

METHODS

The study cohort consisted of 193 subjects after Magmaris implantation and 160 patients following Absorb implantation in large-vessel lesions.

RESULTS

At 2 years, a significantly lower rate of a primary outcome (cardiac death, myocardial infarction, stent thrombosis) was observed with Magmaris (5.2% vs. 15%; p = 0.002). In addition, we observed a significantly lower rate of MI in the target vessel (2.6% vs. 9.4%; p = 0.009) and a lower rate of scaffold thrombosis (0% vs. 3.7%; p = 0.008). The TLF rate between the two groups was not significantly different.

CONCLUSION

Magmaris demonstrated a good safety profile and more favorable clinical outcomes when compared to Absorb in patients with non-ST-elevation ACS.

Long-Term Outcomes After Implantation of Magnesium-Based Bioresorbable Scaffolds—Insights From an All-Comer Registry

Background

The magnesium-based sirolimus-eluting bioresorbable scaffold (Mg-BRS) Magmaris™ showed promising clinical outcomes, including low rates of both the target lesion failure (TLF) and scaffold thrombosis (ScT), in selected study patients. However, insights regarding long-term outcomes (>2 years) in all-comer populations remain scarce.

Methods

We analyzed data from a single-center registry, including patients with acute coronary syndrome (ACS) and chronic coronary syndrome (CCS), who had undergone percutaneous coronary intervention (PCI) using the Mg-BRS. The primary outcome comprised the device-oriented composite endpoint (DoCE) representing a hierarchical composite of cardiac death, ScT, target vessel myocardial infarction (TV-MI), and clinically driven target lesion revascularization (TLR) up to 5 years.

Results

In total, 84 patients [mean age 62 ± 11 years and 63 (75%) men] were treated with the Mg-BRS devices between June 2016 and March 2017. Overall, 101 lesions had successfully been treated with the Mg-BRS devices using 1.2 ± 0.4 devices per lesion. Pre- and postdilatation using dedicated devices had been performed in 101 (100%) and 98 (97%) of all the cases, respectively. After a median follow-up time of 62 (61–64) months, 14 (18%) patients had experienced DoCEs, whereas ScT was encountered in 4 (4.9%) patients [early ScTs (<30 days) in three cases and two fatal cases]. In 4 (29%) of DoCE cases, optical coherence tomography confirmed the Mg-BRS collapse and uncontrolled dismantling.

Conclusion

In contradiction to earlier studies, we encountered a relatively high rate of DoCEs in an all-comer cohort treated with the Mg-BRS. We even observed scaffold collapse and uncontrolled dismantling. This implicates that this metal-based BRS requires further investigation and may only be used in highly selected cases.

Optical coherence tomography versus angiography guided magnesium bioresorbable scaffold implantation in NSTEMI patients

BACKGROUND

The purpose of a bioresorbable scaffold (BRS) is to provide radial support during coronary healing. In this study, coronary artery healing after optical coherence tomography (OCT)- versus angiography-guided magnesium BRS (MBRS) implantation in patients with non-ST-segment-elevation myocardial infarction (NSTEMI) is compared.

METHODS

75 patients were randomized 1:1 to OCT- or angiography-guided implantation of a MBRS with protocolled pre- and post-dilation. In the OCT-guided group, prespecified criteria indicating additional intervention were (1) scaffold under-expansion, (2) strut malapposition, (3) edge dissection, and (4) residual stenosis at distal or proximal reference segments. The primary endpoint was OCT-derived healing stage at 6 months.

RESULTS

At 6 months, there was no difference in average healing stage between OCT- and angiography-guided intervention (4.6 [interquartile range (IQR): 4.5-4.7] versus 4.5 [IQR: 4.3-4.7]; p = 0.54). The MBRSs were completely resolved in 77.0% [IQR: 68.5-85.5] versus 76.5% [IQR: 67.9-85.5]; (p = 0.97). Minimal lumen area (MLA) was reduced at 6 months in both the OCT- (32.3%; p < 0.01) and the angiography-guided group (21.3%; p < 0.01), however OCT-guided implantation was associated with a greater reduction of total lumen volume (-27.1 ± 32.5 mm³ versus -5.0 ± 32.9 mm³; p < 0.01) and MLA (-2.3 ± 1.6 mm² vs. -1.4 ± 1.4 mm²; p = 0.02).

CONCLUSIONS

In NSTEMI patients, OCT-guidance with protocolled pre- and post-dilation of MBRS implantation showed similar healing pattern at 6 months compared to angiography-guidance alone.

CLINICAL TRIAL REGISTRATION

The Coronary Artery Healing Process after Optical Coherence Tomography Guided Percutaneous Coronary Intervention with Magmaris Bioresorbable Scaffold in Patients with Non-ST-Segment-Elevation Myocardial Infarction: (HONEST) trial is registered with ClinicalTrials.gov, NCT03016624.

First-in-Man trial of a drug-free bioresorbable stent designed to minimize the duration of coronary artery scaffolding

For the last two decades, various degradable stents have been proposed to treat coronary artery diseases and replace metallic stents to avoid residual foreign material after healing. To date, the right balance between suitable scaffolding and loss of radial strength soon after endothelium restoration is still an unmet need. The present article reports on the First-in-Man trial of a drug-free bioresorbable stent based on a lactic acid stereocopolymer composed of 98% l-lactyl units selected to release stress shielding earlier than in the case of homopoly(l-lactic acid). Thirty patients with single de novo coronary lesions were included in the trial. The fate of scaffolds was monitored by clinical and imaging follow-ups to assess rate of adverse events, acute recoil, late luminal loss, and late lumen recovery. There was no death, no myocardial infarction, and no stent thrombosis observed over the 36 months trial. Dismantling occurred about 3 months after implantation. Bioresorption was almost completed at 2 years. The late lumen loss observed at the end of the first year was partly compensated one year later by enlarging remodeling. At one year, a neointimal hyperplasia slightly greater than for drug-eluting metallic and bioresorbable stents was shown using optical coherence tomography. The excess of hyperplasia was discussed relative to struts thickness, absence of anti-proliferative drug, and release of degradation by-products.

Current perspectives on bioresorbable scaffolds in coronary intervention and other fields

Introduction: The first-generation bioresorbable scaffolds (BRSs) had a large strut profile to compensate for the insufficient radial strength of bioresorbable polymer materials, resulting in higher scaffold thrombosis rates than conventional drug-eluting stents. To improve the clinical safety and efficacy, the new generation BRSs have been improved by optimal structure design, post-processing of bioresorbable polymer materials, or altering bioresorbable metallic alloys.Areas covered: This review summarizes the lessons learned from the first-generation BRS, updates the clinical outcomes of trials evaluating ABSORB bioresorbable vascular scaffold at long-term and bioresorbable metallic alloy-based devices, and examines recent outcomes of BRS treated in STEMI patients. This review also provides an overview of the current clinical data of seven BRSs manufactured in Asia, and of the BRSs extended application in other clinical arenas.Expert opinion: Drawbacks of the first-generation BRSs need to be addressed by the next generation of these stents with novel materials and technologies. Clinical research, including randomized controlled trials, are required to further evaluate BRSs application in coronary artery disease. The encouraging results of BRSs innovation applied in the peripheral arteries and gastrointestinal tracts support other potential clinical applications of BRS technology.

Coronary Artery Healing Process after Bioresorbable Scaffold in Patients with Non-ST-Segment Elevation Myocardial Infarction: Rationale, Design, and Methodology of the HONEST Study

BACKGROUND

Bioresorbable scaffolds (BRSs) is a relatively new approach in treating coronary artery stenosis. The initial results of the first commercially available scaffolds consisting of a backbone of poly-L-lactide raised safety concerns related to delayed resorption and healing. The magnesium alloy-based scaffold degrades via bio-corrosion within months, whereas it often takes several years for polymer scaffolds to degrade. The aim of the study was to assess the healing stage by optical coherence tomography (OCT) after 6 months in patients with non-ST-segment elevation myocardial infarct (NSTEMI) randomized to OCT or angiography-guided percutaneous coronary intervention with implantation of a magnesium sirolimus-eluting Magmaris scaffold (Magmaris; Biotronik, Bülach, Switzerland).

METHODS

We analyzed the healing process by comparing OCT at baseline and after 6 months. Five stages of healing were defined with stage 1 being the least healed and stage 5 demonstrating complete resorption and healing with no visible scaffold/remnant. The primary end point is a calculated healing score that is based on 5 subtypes of healing stage: (1) malapposed, (2) uncovered with no detection of smooth surface tissue on top of struts or remnants, (3) covered protruding, (4) covered embedded, and (5) complete healing with a smooth neointimal surface and no sign of struts or visible remnants assessed by OCT 6 months after the index procedure.

RESULTS

The impact of OCT-guided compared to angiography-guided scaffold implantation will be illuminated.

CONCLUSION

The present study will provide new information on midterm healing properties of the magnesium BRS in patients with NSTEMI.

Inflammation as a determinant of healing response after coronary stent implantation

Cardiovascular disease remains the leading cause of death and morbidity worldwide. Inflammation plays an important role in the development of atherosclerosis and is associated with adverse clinical outcomes in patients after percutaneous coronary interventions. Data on stent elements that lead to excessive inflammatory response, proper identification of high-risk patients, prevention and treatment targeting residual inflammatory risk are limited. This review aims to present the role of inflammation in the context of evolving stent technologies and appraise the potential imaging modalities in detection of inflammatory response and anti-inflammatory therapies.

The 2010s in clinical drug-eluting stent and bioresorbable scaffold research: a Dutch perspective

Dutch researchers were among the first to perform clinical studies in bare metal coronary stents, the use of which was initially limited by a high incidence of in-stent restenosis. This problem was greatly solved by the introduction of drug-eluting stents (DES). Nevertheless, enthusiasm about first-generation DES was subdued by discussions about a higher risk of very-late stent thrombosis and mortality, which stimulated the development, refinement, and rapid adoption of new DES with more biocompatible durable polymer coatings, biodegradable polymer coatings, or no coating at all. In terms of clinical DES research, the 2010s were characterised by numerous large-scale randomised trials in all-comers and patients with minimal exclusion criteria. Bioresorbable scaffolds (BRS) were developed and investigated. The Igaki-Tamai scaffold without drug elution was clinically tested in the Netherlands in 1999, followed by an everolimus-eluting BRS (Absorb) which showed favourable imaging and clinical results. Afterwards, multiple clinical trials comparing Absorb and its metallic counterpart were performed, revealing an increased rate of scaffold thrombosis during follow-up. Based on these studies, the commercialisation of the device was subsequently halted. Novel technologies are being developed to overcome shortcomings of first-generation BRS. In this narrative review, we look back on numerous devices and on the DES and BRS trials reported by Dutch researchers.

Sustained Safety and Performance of the Second-Generation Sirolimus-Eluting Absorbable Metal Scaffold: Pooled Outcomes of the BIOSOLVE-II and -III Trials at 3 Years

BACKGROUND/PURPOSE

To avoid long-term effects associated with permanent implants, bioresorbable vascular scaffolds were developed, as they provide transient vessel support and disappear thereafter. The aim of the BIOSOLVE-II and -III studies was to assess the safety and performance of a magnesium-based sirolimus-eluting scaffold; we report the clinical outcomes at 3 years, 2 years after scaffold resorption.

METHODS/MATERIALS

BIOSOLVE-II and BIOSOLVE-III are international, prospective multi-center studies, including 184 patients with 189 de novo lesions and stable or unstable angina, or documented silent ischemia. Acute myocardial infarction, 3-vessel coronary artery disease, and heavily calcified lesions were excluded. Antiplatelet therapy was recommended for 6 months.

RESULTS

Patients were 65.5 ± 10.8 years old, and lesions were 12.1 ± 4.5 mm long and located in vessels with a diameter of 2.7 ± 0.4 mm. More than half of the lesions (56.5%) were type B2/C lesions. At 2 years, 92.5% (160/173) of patients were symptom-free and 91.5% (151/165) at 3 years; all the other patients had stable angina. At 3 years, target lesion failure occurred in 11 patients (6.3%), consisting of 4 cardiac deaths (2.3%), one target-vessel myocardial infarction (0.6%), and 6 clinically driven target lesion revascularizations (3.4%). There was no definite or probable scaffold thrombosis.

CONCLUSION

In a low-risk patient population, treatment with a sirolimus-eluting magnesium bioresorbable scaffold can be considered safe, in particular with no definite or probable scaffold thrombosis.

ANNOTATED TABLE OF CONTENTS

BIOSOLVE-II and -III are prospective, international, multi-center studies including 184 patients with de novo lesions. At 3 years, target lesion failure was 6.3%, consisting of 4 cardiac deaths (2.3%), one target-vessel myocardial infarction (0.6%), and 6 clinically driven target lesion revascularizations (3.4%). There was no definite or probable scaffold thrombosis.