Possible mechanical causes of scaffold thrombosis: insights from case reports with intracoronary imaging

Very late Magmaris scaffold restenosis: a 6-year serial optical coherence tomography case report

Background

Bioresorbable scaffolds (BRS) have been proposed as an alternative to drug-eluting stents (DES), offering radial support during the early phases of healing, while potentially reducing the risk of long-term complications. A magnesium-based BRS (MgBRS) has shown promising results after implantation. However, there is a lack of knowledge regarding the long-term outcomes.

Case summary

A 62-year-old man with hypertension, dyslipidaemia, family history of ischaemic heart disease, and previous myocardial infarction, presented with non-ST-elevation myocardial infarction (NSTEMI). Six years prior, he also had a NSTEMI and a mid-left anterior descending artery (LAD) lesion was treated with a 3.0/25 mm MgBRS. Post-implantation optical coherence tomography (OCT) revealed proximal edge dissection, and a second MgBRS 3.0/15 mm was implanted. Optical coherence tomography of the scaffold-treated segment was performed after 6 and 12 months with no sign of restenosis. The current angiogram showed a restenosis in the previously MgBRS-treated segment in LAD. Optical coherence tomography showed a plaque rupture in a thin cap fibro-atheroma and scaffold remnants. The lesion was pre-dilated and stented with a 3.0/20 mm DES and post-dilated with a 3.5 mm non-compliant balloon.

Discussion

Most cases of late scaffold failure showed acquired mal-apposition, which also can be related to the degrading process, or uncovered struts, none of which were seen in our case at 6 or 12 months. This case represents an insight into the vascular healing and potential mechanisms for failure of the MgBRS, with serial OCT recording at implantation, and after 6 months, 12 months, and 6 years.

The Absorb GT1 Bioresorbable Vascular Scaffold System - 5-Year Post-Market Surveillance Study in Japan

BACKGROUND

The 1-year clinical outcomes of the Absorb GT1 Japan post-market surveillance (PMS) suggested that an appropriate intracoronary imaging-guided bioresorbable vascular scaffold (BVS) implantation technique may reduce the risk of target lesion failure (TLF) and scaffold thrombosis (ST) associated with the Absorb GT1 BVS. The long-term outcomes through 5 years are now available.Methods and Results: This study enrolled 135 consecutive patients (n=139 lesions) with ischemic heart disease in whom percutaneous coronary intervention (PCI) with the Absorb GT1 BVS was attempted. Adequate lesion preparation, imaging-guided appropriate sizing, and high-pressure post-dilatation using a non-compliant balloon were strongly encouraged. All patients had at least 1 Absorb GT1 successfully implanted at the index procedure. Intracoronary imaging was performed in all patients (optical coherence tomography: 127/139 [91.4%] lesions) and adherence to the implantation technique recommendations was excellent: predilatation, 100% (139/139) lesions; post-dilatation, 98.6% (137/139) lesions; mean (±SD) post-dilatation pressure, 18.8±3.5 atm. At 5 years, the follow-up rate was 87.4% (118/135). No definite/probable ST was reported through 5 years. The cumulative TLF rate was 5.1% (6/118), including 2 cardiac deaths, 1 target vessel-attributable myocardial infarction, and 3 ischemia-driven target lesion revascularizations.

CONCLUSIONS

Appropriate intracoronary imaging-guided BVS implantation, including the proactive use of pre- and post-balloon dilatation during implantation may be beneficial, reducing the risk of TLF and ST through 5 years.

Safety and efficacy of a novel 3D-printed bioresorbable sirolimus-eluting scaffold in a porcine model

Background

The effect of 3D-printed bioresorbable vascular scaffolds (BRS) in coronary heart disease has not been clarified.

Aims

We aimed to compare the safety and efficacy of 3D-printed BRS with that of metallic sirolimus-eluting stents (SES).

Methods

Thirty-two BRS and 32 SES were implanted into 64 porcine coronary arteries. Quantitative coronary angiography (QCA) and optical coherence tomography (OCT) were performed at 14, 28, 97, and 189 days post-implantation. Scanning electron microscopy (SEM) and histopathological analyses were performed at each assessment.

Results

All stents/scaffolds were successfully implanted. All animals survived for the duration of the study. QCA showed the two devices had a similar stent/scaffold-to-artery ratio and acute percent recoil. OCT showed the lumen area (LA) and scaffold/stent area (SA) of the BRS were significantly smaller than those of the SES at 14 and 28 days post-implantation (14-day LA: BRS vs SES 4.52±0.41 mm2 vs 5.69±1.11 mm2; p=0.03; 14-day SA: BRS vs SES 4.99±0.45 mm2 vs 6.11±1.06 mm2; p=0.03; 28-day LA: BRS vs SES 2.93±1.03 mm2 vs 4.82±0.74 mm2; p=0.003; 28-day SA: BRS vs SES 3.86±0.98 mm2 vs 5.75±0.71 mm2; p=0.03). Both the LA and SA of the BRS increased over time and were similar to those of the SES at the 97-day and 189-day assessments. SEM and histomorphological analyses showed no significant between-group differences in endothelialisation at each assessment.

Conclusions

The novel 3D-printed BRS showed safety and efficacy similar to that of SES in a porcine model. The BRS also showed a long-term positive remodelling effect.

5-Year Outcomes After Bioresorbable Coronary Scaffolds Implanted With Improved Technique

BACKGROUND

Bioresorbable vascular scaffolds (BVS) were designed to improve late event-free survival compared with metallic drug-eluting stents. However, initial trials demonstrated worse early outcomes with BVS, in part due to suboptimal technique. In the large-scale, blinded ABSORB IV trial, polymeric everolimus-eluting BVS implanted with improved technique demonstrated noninferior 1-year outcomes compared with cobalt chromium everolimus-eluting stents (CoCr-EES).

OBJECTIVES

This study sought to evaluate the long-term outcomes from the ABSORB IV trial.

METHODS

We randomized 2,604 patients at 147 sites with stable or acute coronary syndromes to BVS with improved technique vs CoCr-EES. Patients, clinical assessors, and event adjudicators were blinded to randomization. Five-year follow-up was completed.

RESULTS

Target lesion failure at 5 years occurred in 216 (17.5%) patients assigned to BVS and 180 (14.5%) patients assigned to CoCr-EES (P = 0.03). Device thrombosis within 5 years occurred in 21 (1.7%) BVS and 13 (1.1%) CoCr-EES patients (P = 0.15). Event rates were slightly greater with BVS than CoCr-EES through 3-year follow-up and were similar between 3 and 5 years. Angina, also centrally adjudicated, recurred within 5 years in 659 patients (cumulative rate 53.0%) assigned to BVS and 674 (53.3%) patients assigned to CoCr-EES (P = 0.63).

CONCLUSIONS

In this large-scale, blinded randomized trial, despite the improved implantation technique, the absolute 5-year rate of target lesion failure was 3% greater after BVS compared with CoCr-EES. The risk period for increased events was limited to 3 years, the time point of complete scaffold bioresorption; event rates were similar thereafter. Angina recurrence after intervention was frequent during 5-year follow-up but was comparable with both devices.(Absorb IV Randomized Controlled Trial; NCT02173379).

Preclinical evaluation of the degradation kinetics of third-generation resorbable magnesium scaffolds

BACKGROUND

The novel sirolimus-eluting resorbable scaffold DREAMS 3G was designed as a third-generation development of its predecessor, the Magmaris scaffold.

AIMS

This preclinical study aimed to examine the qualitative and temporal course of the degradation of the DREAMS 3G relative to the Magmaris scaffold.

METHODS

Forty-nine DREAMS 3G and 24 Magmaris scaffolds were implanted into 48 mini swine for degradation kinetics analysis. Another DREAMS 3G was implanted into one mini swine for crystallinity analysis of the degradation end product after 730 days. Degradation kinetics were determined at 28, 90, 120, 180, and 365 days.

RESULTS

Discontinuity density in DREAMS 3G was significantly lower than that in Magmaris scaffolds for the follow-up timepoints of 90 and 120 days. Planimetric analysis indicated 99.6% backbone degradation for DREAMS 3G at 12 months. Compared to the Magmaris scaffold, individual strut degradation in DREAMS 3G showed less variability and the remaining backbone core was more homogeneous. The degradation end product of DREAMS 3G manifested as calcium phosphate with a minor share of aluminium phosphate.

CONCLUSIONS

DREAMS 3G showed almost complete degradation after one year, with amorphous calcium and aluminium phosphate as the end products of degradation. Despite its thinner struts, scaffold discontinuity was significantly lower in the DREAMS 3G than in the Magmaris scaffold, likely providing a longer scaffolding time.

Safety and Efficacy of Everolimus-Eluting Bioresorbable Vascular Scaffold Versus Second-Generation Drug-Eluting Stents in Real-World Practice

BACKGROUND

The risk of device thrombosis and device-oriented clinical outcomes with bioresorbable vascular scaffold (BVS) was reported to be significantly higher than with contemporary drug-eluting stents (DESs). However, optimal device implantation may improve clinical outcomes in patients receiving BVS. The current study evaluated mid-term safety and efficacy of Absorb BVS with meticulous device optimization under intravascular imaging guidance.

METHODS

The SMART-REWARD and PERSPECTIVE-PCI registries in Korea prospectively enrolled 390 patients with BVS and 675 patients with DES, respectively. The primary endpoint was target vessel failure (TVF) at 2 years and the secondary major endpoint was patient-oriented composite outcome (POCO) at 2 years.

RESULTS

Patient-level pooled analysis evaluated 1,003 patients (377 patients with BVS and 626 patients with DES). Mean scaffold diameter per lesion was 3.24 ± 0.30 mm in BVS group. Most BVSs were implanted with pre-dilatation (90.9%), intravascular imaging guidance (74.9%), and post-dilatation (73.1%) at proximal to mid segment (81.9%) in target vessel. Patients treated with BVS showed comparable risks of 2-year TVF (2.9% vs. 3.7%, adjusted hazard ratio [HR], 1.283, 95% confidence interval [CI], 0.487-3.378, P = 0.615) and 2-year POCO (4.5% vs. 5.9%, adjusted HR, 1.413, 95% CI, 0.663-3.012, P = 0.370) than those with DES. The rate of 2-year definite or probable device thrombosis (0.3% vs. 0.5%, P = 0.424) was also similar. The sensitivity analyses consistently showed comparable risk of TVF and POCO between the 2 groups.

CONCLUSION

With meticulous device optimization under imaging guidance and avoidance of implantation in small vessels, BVS showed comparable risks of 2-year TVF and device thrombosis with DES.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02601404, NCT04265443.

Challenges of the newer generation of resorbable magnesium scaffolds: Lessons from failure mechanisms of the past generation

Bioresorbable scaffolds (BRS) were developed to overcome the obstacles of metallic stents, mostly related to sustained presence of metallic foreign body in the coronary vessel. Following earlier success of single-arm BRS studies, randomized controlled trials of Absorb bioresorbable vascular scaffold (Abbott Vascular, Santa Clara, CA, USA) showed poor long-term clinical outcomes, particularly in terms of scaffold thrombosis. BRS made from magnesium alloy provide a promising alternative in terms of radial force, strut thickness and, potentially lower thrombogenicity. A recent clinical study demonstrated that magnesium-based BRS seems to be promising with regards to the risk of scaffold thrombosis. In this review, our aim is to describe the issues that prevented Absorb BVS from achieving favorable outcomes, provide current status of existing BRS technologies and the challenges that newer generation BRSs need to overcome, and the results of clinical studies for commercially available magnesium-based BRS, which remain the only BRS actively studied in clinical practice.

Structural and Functional Evaluation of Coronary Arteries Treated With ABSORB Bioresorbable Vascular Scaffold at 5-Year Follow-Up

Although complete bioresorbable vascular scaffold (BVS) resorption has been demonstrated at 5-year follow-up, whether corresponding vasomotor function restoration occurs remains unknown. The objective was to simultaneously assess the structural healing response along with vasomotor responses at 5-year follow-up of BVS implantation. We studied consecutive patients treated with ABSORB-BVS at 5-year follow-up (n = 31), who were recruited from a multicenter registry and were contacted to undergo a research protocol-driven repeat coronary angiogram involving intracoronary optical coherence tomography (OCT) and invasive coronary endothelial function testing. Epicardial endothelium-dependent vasomotion was defined as any vasodilatation after intracoronary acetylcholine (ACh), whereas endothelium-independent vasomotion was defined as any vasodilatation after intracoronary nitroglycerine (NTG), using quantitative coronary angiography. The mean implantation time point was 60.5 ± 4.6 months. OCT imaging demonstrated complete scaffold resorption in all patients. New coronary lesions (stenosis >50%) were found in 5 patients (16.1%), 3 of them underwent ad hoc percutaneous revascularization (9.7%). Intracoronary ACh (27 patients) and NTG testing (30 patients) was performed. Quantitative coronary angiography analysis demonstrated vasoconstriction after ACh administration and lack of response to NTG in BVS segments (mean lumen diameter = 2.00 ± 0.61 mm at baseline vs 1.74 ± 0.70 mm post-ACh, p <0.001; 2.05 ± 0.54 mm at baseline vs 2.03 ± 0.50 mm post-NTG, p = 0.69). OCT lumen analysis demonstrated similar vasoconstrictive responses to ACh (mean lumen area = 5.31 ± 2.26 mm² at baseline vs 5.12 ± 2.55 mm² post-ACh, p = 0.007) but had a vasodilatory response to NTG (5.96 ± 2.35 mm² at baseline vs 6.17 ± 2.55 mm² post-NTG, p<0.001). In conclusion, complete ABSORB-BVS resorption was demonstrated at 5-year follow-up. However, this healing response was associated with endothelium-dependent vasomotor dysfunction within the BVS segment.

Outcomes of the two generations of bioresorbable scaffolds (Magmaris vs. Absorb) in acute coronary syndrome in routine clinical practice

BACKGROUND

Acute coronary syndrome (ACS) as a clinical manifestation of coronary artery disease (CAD) remains a significant cause of mortality and morbidity, as reported worldwide annually. The second generation of drug-eluting stents (DES) is a gold standard in percutaneous interventions in ACS patients however, permanent caging of the vessel with metallic DES has some drawbacks. Bioresorbable vascular scaffolds (BRS) were designed as a temporal vessel-supporting technology allowing for anatomical and functional restoration. Nevertheless, following the initial encouraging reports, numerous concerns about the safety of BRS occurred.

METHODS

In this study, a 1-year performance of 193 patients with magnesium BRS - Magmaris (Biotronik, Berlin, Germany) was evaluated in comparison to 160 patients with polymer BRS - Absorb (Abbott-Vascular, Chicago, USA) in the non-ST-segment elevation-ACS setting.

RESULTS

The Magmaris, when compared to Absorb showed a significantly lower rate of primary endpoint (death from cardiac causes, myocardial infarction, stent thrombosis) as well as target lesion failure in 30-day and 1 year follow-up. In the Absorb group, a significantly higher rate of stent thrombosis was observed.

CONCLUSIONS

Data from the present study suggests encouraging safety a profile and more favorable clinical outcomes of Magnesium BRS in comparison to the polymer Absorb - BRS.

Effects of aggressive predilatation, sizing, and postdilatation strategy for coronary bioresorbable vascular scaffolds implantation

BACKGROUND

The results of the recent Amsterdam Investigator-Initiated Absorb Strategy All-Comers trial showed that the predilatation, sizing, and postdilatation (PSP) technique did not lower the long-term rates of scaffold thrombosis and adverse events. We evaluated the impact of aggressive PSP bioresorbable vascular scaffold (BRS) implantation on the short- and long-term clinical outcomes.

METHODS

From June 2014 to December 2016, 150 patients with BRS implantation were enrolled and received successful percutaneous coronary intervention (PCI), of whom 104 received aggressive PSP technique (high-pressure predilatation and lesion preparation in addition to the traditional PSP technique). Short- and long-term outcomes were compared.

RESULTS

All patients underwent successful PCI and BRS implantation with final Thrombolysis in Myocardial Infarction grade 3 flow. The baseline and procedure characteristics were similar in both groups. Debulking techniques were used in 13 (8.7%) patients. Intracoronary imaging modalities were used in 73 (48.7%) patients. After BRS implantation, no adverse events were observed within 30 days in both groups. During the mean follow-up period of 2.98 ± 0.77 years, 12 (8.0%) patients experienced major adverse cardiovascular events (MACEs), including one cardiovascular death (0.6%), three nonfatal myocardial infarction (2.0 %), and 11 target-vessel revascularization (7.3 %). Multivariate Cox regression analysis showed that aggressive PSP remained an independent protective factor for MACEs. Moreover, the use of intracoronary imaging and rotablation atherectomy was associated with better clinical outcomes.

CONCLUSION

Lesion preparation by aggressive PSP in BRS implantation was associated with better long-term clinical outcomes.

Long-term clinical outcomes of everolimus-eluting bioresorbable scaffolds versus everolimus-eluting stents: final five-year results of the AIDA randomised clinical trial

BACKGROUND

Absorb bioresorbable vascular scaffold (BVS)-related events have been reported between 1 and 3 years - the period of active scaffold bioresorption. Data on the performance of the Absorb BVS in daily clinical practice beyond this time point are scarce.

AIMS

This report aimed to provide the final five-year clinical follow-up of the Absorb BVS in comparison with the XIENCE everolimus-eluting stent (EES). In addition, we evaluated the effect of prolonged dual antiplatelet therapy (DAPT) administration on events in the scaffold group.

METHODS

AIDA was a multicentre, investigator-initiated, non-inferiority trial, in which 1,845 unselected patients with coronary artery disease were randomly assigned to either the Absorb BVS (n=924) or the XIENCE EES (n=921). Target vessel failure (TVF), a composite of cardiac death, target vessel myocardial infarction or target vessel revascularisation, was the primary endpoint. Scaffold thrombosis cases were matched with controls and tested for the effect of prolonged DAPT.

RESULTS

Up to five-year follow-up, there was no difference in TVF between the Absorb BVS (17.7%) and the XIENCE EES (16.1%) (hazard ratio [HR] 1.31, 95% confidence interval [CI]: 0.90-1.41; p=0.302). Definite or probable device thrombosis (DT) occurred in 43 patients (4.8%) in the scaffold group compared to 13 patients (1.5%) in the stent group (HR 3.32, 95% CI: 1.78-6.17; p<0.001). DT between 3 and 4 years occurred six times in the Absorb arm versus three times in the XIENCE arm. Between 4 and 5 years, the incidence was three versus two, respectively. Of those three DT in the scaffold group, two occurred in XIENCE EES-treated lesions. The odds ratio of scaffold thrombosis in patients on DAPT compared to off DAPT throughout five-year follow-up was 0.36 (95% CI: 0.15-0.86).

CONCLUSIONS

The excess risk of the Absorb BVS on late adverse events, in particular device thrombosis, in routine PCI continues up to 4 years and seems to plateau afterwards. Clinical Trial Registration ClinicalTrials.gov: NCT01858077.

Amphiphilic Core Cross-Linked Star Polymers for the Delivery of Hydrophilic Drugs from Hydrophobic Matrices

The delivery of hydrophilic drugs from hydrophobic polymers is a long-standing challenge in the biomaterials field due to the limited solubility of the therapeutic agent within the polymer matrix. In this work, we develop a drug delivery mechanism that enables the impregnation and subsequent elution of hydrophilic drugs from a hydrophobic polymer material. This was achieved by synthesizing core cross-linked star polymer amphiphiles with hydrophilic cores and hydrophobic coronas. While significant work has been done to create nanocarriers for hydrophilic drugs, this work is distinct from previous work in that it designs amphiphilic and core cross-linked particles for controlled release from hydrophobic matrices. Ultraviolet-mediated atom transfer radical polymerization was used to synthesize the poly(ethylene glycol) (PEG)-based hydrophilic cores of the star polymers, and hydrophobic coronas of poly(caprolactone) (PCL) were then built onto the stars using ring-opening polymerization. We illustrated the cytocompatibility of PCL loaded with these star polymers through human endothelial cell adhesion and proliferation for up to 7 days, with star loadings of up to 40 wt %. We demonstrated successful loading of the hydrophilic drug heparin into the star polymer core, achieving a loading efficiency and content of 50 and 5%, respectively. Finally, the heparin-loaded star polymers were incorporated into a PCL matrix and sustained release of heparin was illustrated for over 40 days. These results support the use of core cross-linked star polymer amphiphiles for the delivery of hydrophilic drugs from hydrophobic polymer matrices. These materials were developed for application as drug-eluting and biodegradable coronary artery stents, but this flexible drug delivery platform could have impact in a broad range of medical applications.

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.

Multimodal Loading Environment Predicts Bioresorbable Vascular Scaffolds' Durability

Bioresorbable vascular scaffolds were considered the fourth generation of endovascular implants deemed to revolutionize cardiovascular interventions. Yet, unexpected high risk of scaffold thrombosis and post-procedural myocardial infractions quenched the early enthusiasm and highlighted the gap between benchtop predictions and clinical observations. To better understand scaffold behavior in the mechanical environment of vessels, animal, and benchtop tests with multimodal loading environment were conducted using industrial standard scaffolds. Finite element analysis was also performed to study the relationship among structural failure, scaffold design, and load types. We identified that applying the combination of bending, axial compression, and torsion better reflects incidence observed in-vivo, far more than tranditional single mode loads. Predication of fracture locations is also more accurate when at least bending and axial compression are applied during benchtop tests (>60% fractures at connected peak). These structural failures may be initiated by implantation-induced microstructural damages and worsened by cyclic loads from the beating heart. Ignoring the multi-modal loading environment in benchtop fatigue tests and computational platforms can lead to undetected potential design defects, calling for redefining consensus evaluation strategies for scaffold performance. With the robust evaluation strategy presented herein, which exploits the results of in-vivo, in-vitro and in-silico investigations, we may be able to compare alternative designs of prototypes at the early stages of device development and optimize the performance of endovascular implants according to patients-specific vessel dynamics and lesion configurations in the future.

Randomized Comparison Between Everolimus-Eluting Bioresorbable Scaffold and Metallic Stent: Multimodality Imaging Through 3 Years

OBJECTIVES

The aim of this study was to investigate the vascular responses and fates of the scaffold after bioresorbable vascular scaffold (BVS) implantation using multimodality imaging.

BACKGROUND

Serial comprehensive image assessments after BVS implantation in the context of a randomized trial have not yet been reported.

METHODS

In the ABSORB Japan trial, 400 patients were randomized to a BVS (n = 266) or a cobalt-chromium everolimus-eluting stent (n = 134). Through 3 years, patients underwent serial angiography and intravascular ultrasound or optical coherence tomography (OCT).

RESULTS

Luminal dimension at 3 years was consistently smaller with the BVS than with the cobalt-chromium everolimus-eluting stent (mean angiographic minimal luminal diameter 2.04 ± 0.63 mm vs. 2.40 ± 0.56 mm, mean difference -0.37 mm [95% confidence interval: -0.50 to -0.24 mm]; p < 0.001), mainly because of smaller device area (6.13 ± 2.03 mm² vs. 7.15 ± 2.16 mm², mean difference -1.04 mm² [95% confidence interval: -1.66 to -0.42 mm²]; p < 0.001), and larger neointimal area (2.10 ± 0.61 mm² vs. 1.86 ± 0.64 mm², mean difference 0.24 mm² [95% confidence interval: 0.06 to 0.43 mm²]; p = 0.01) by OCT. BVS-treated vessels did not show previously reported favorable vessel responses, such as positive vessel remodeling, late luminal enlargement, and restoration of vasomotion, although the OCT-based healing score was on average zero (interquartile range: 0.00 to 0.00). At 3 years, intraluminal scaffold dismantling (ISD) was observed in 14% of BVS. On serial OCT, ISD was observed in 6 lesions at 2 years, where the struts had been fully apposed at post-procedure, while ISD was observed in 12 lesions at 3 years, where 8 lesions were free from ISD on 2-year OCT. In 5 cases of very late scaffold thrombosis, strut discontinuities were detected in all 4 cases with available OCT immediately before reintervention.

CONCLUSIONS

In this multimodality serial imaging study, luminal dimension at 3 years was smaller with the BVS than with the cobalt-chromium everolimus-eluting stent. ISD, suspected to be one of the mechanisms of very late BVS thrombosis, was observed in a substantial proportion of cases at 3 years, which developed between post-procedure and 2 years and even beyond 2 years. (AVJ-301 Clinical Trial: A Clinical Evaluation of AVJ-301 [Absorb™ BVS] in Japanese Population [ABSORB JAPAN]; NCT01844284).

Outcomes after complete dissolution of everolimus-eluting bioresorbable scaffolds implanted during routine practice

INTRODUCTION AND OBJECTIVES

Long-term outcomes of unselected patients treated with bioresorbable vascular scaffold (BVS) implantation are lacking, especially for the period after complete dissolution of the BVS. This study sought to evaluate 5-year outcomes in patients treated with BVS in routine practice.

METHODS

Consecutive patients who underwent implantation of everolimus-eluting BVS during routine clinical practice at 2 high-volume centres in Germany were studied. The patients were followed-up for up to 5 years. The primary endpoints of interest were the composite of death, myocardial infarction and target lesion revascularization, as well as definite scaffold thrombosis.

RESULTS

A total of 419 patients (mean age 66.6 ± 10.9 years; 31.5% had diabetes) were included, of whom 38.9% presented with an acute coronary syndrome. Of the 527 lesions treated, 49.0% were classified as complex and 13.1% were bifurcation lesions. At 5 years, the composite clinical endpoint occurred in 33.1% of patients and definite scaffold thrombosis occurred in 4.7%. Most definite scaffold thrombosis occurred within 2 years after BVS implantation.

CONCLUSIONS

In patients treated with BVS implantation in routine clinical practice the rates of adverse clinical events at 5 years were high, including a considerable incidence of scaffold thrombosis.

Mid-term outcomes of bioresorbable vascular scaffolds vs second-generation drug-eluting stents in patients with acute coronary syndromes: A systematic review and meta-analysis

BACKGROUND

Everolimus-eluting bioresorbable vascular scaffolds (BVS), which have the characteristics of scaffold absorption and vascular function recovery, are the latest innovation in the treatment of coronary artery disease. This new concept has become a hot topic in the field of interventional cardiology. Data regarding mid-term clinical outcomes of BVS in acute coronary syndromes are currently scarce. The aim of this systematic review and meta-analysis is to compare mid-term outcome data for BVS and second-generation drug-eluting stents (DES) in the treatment of acute coronary syndromes.

METHODS

We searched PubMed, Embase, the Cochrane Library, Web of Science, and relevant web sites for studies with a follow-up of ≥ 1 years that studied percutaneous coronary interventions with BVS vs second-generation DES in acute coronary syndromes. A meta-analysis was performed with the software RevMan following the standards of the Cochrane Handbook for Systematic Reviews of Interventions 5.1.0.

RESULTS

Five studies, 2 randomized controlled trials, and 3 observational studies, with a total of 1758 patients (BVS n = 917; DES n = 841) and a median follow-up duration of 24 months, were included. BVS, when compared with DES, resulted in higher rates of target lesion revascularization (TLR) (OR, 2.20; 95% CI, 1.12-3.64; P = .02) and stent/scaffold thrombosis (ST/ScT) (OR = 2.35, 95% CI: 1.13-4.89, P = .02). When TLR due to device thrombosis were excluded, the difference in risk estimates between the 2 groups was no longer significant (OR: 1.67, 95% CI: 0.73-3.82, P = .22). The risk for all-cause death (OR = 1.32 95% CI: 0.61-2.88, P = .48), cardiac death (OR = 1.29, 95% CI: 0.58-2.86 P = .52), target vessel myocardial infarction (OR = 1.50, 95% CI: 0.86-2.61, P = .15), and target lesion failure (OR = 1.34, 95% CI: 0.76-2.35, P = .31) did not differ between BVS and DES groups.

CONCLUSION

At mid-term follow-up, BVS had a higher risk of TLR and ST/ScT than the second-generation DES in patients with acute coronary syndromes. ST/ScT was the key factor indicating the decreased safety and effectiveness of BVS relative to DES.

Fully bioresorbable vascular scaffolds: lessons learned and future directions

Fully bioresorbable scaffolds (BRS) were designed to overcome the limitations of metallic drug-eluting stents, which permanently cage the vessel wall, thereby preventing normal coronary vasomotion, preclude bypass grafting and can provoke long-term foreign-body responses. Although multiple scaffolds have been or are in development, the Absorb Bioresorbable Vascular Scaffold (BVS; Abbott Vascular) was the first FDA-approved device and was widely expected to fulfil the dream of interventional cardiologists of a transient scaffold that would disappear 'when the job was done' and would not hamper further treatment options. Although early, small studies and even large, randomized trials showed beneficial outcomes up to 1 year of follow-up, longer-term results have been disappointing, with increased rates of device thrombosis and target-lesion revascularization. The Absorb BVS device was withdrawn from the market because of low demand. In this Review, we summarize the preclinical and clinical data available for BRS to understand how the vascular biological reactions to these devices differ from biological reactions to metallic drug-eluting stents and how these responses translate into clinical outcomes. We also discuss next-generation BRS and outline modifications that are needed to improve the long-term outcomes with these devices so that they eventually become a viable option for patients with symptomatic obstructive coronary artery disease.

Optical Coherence Tomography for Coronary Bioresorbable Vascular Scaffold Implantation: A Randomized Controlled Trial

BACKGROUND

We investigated whether optical coherence tomography (OCT) guidance would reduce nonoptimal bioresorbable vascular scaffold (BVS) deployment.

METHODS

This was a randomized controlled trial. Patients who required percutaneous coronary intervention for ischemic heart disease were recruited from 2 centers in Korea. The enrolled patients were randomly assigned to receive either OCT-guided BVS (Absorb; Abbott Vascular) implantation or angiography-guided BVS implantation using an optimized technique. The primary outcome was nonoptimal deployment, which was a composite outcome of the following parameters assessed by OCT: a minimal scaffold area <5 mm², residual area stenosis >20%, incomplete apposition of the scaffold struts >5%, major edge dissection, or scaffold disruption. The secondary outcome was a procedural complication defined by the occurrence of no reflow, coronary perforation, or flow-limiting dissection.

RESULTS

Between September 2016 and January 2018, 88 patients (90 lesions) were assigned to OCT guidance, while 88 patients (89 lesions) were assigned to angiography guidance. The recruitment was prematurely terminated in March 2018 because the manufacturer stopped supplying BVS. Postprocedural OCT data were available for 88 lesions with OCT guidance and for 88 lesions with angiography guidance. There was nonoptimal BVS deployment postprocedurally in 35.2% of patients in the OCT-guidance group and in 38.6% in the angiography-guidance group (absolute difference, -3.7% [95% CI, -19.0% to 11.6%]; P=0.64). There were no procedural complications in either group.

CONCLUSIONS

OCT-guided BVS implantation did not reduce the incidence of nonoptimal deployment compared to that of angiography-guided BVS implantation (using optimized techniques).

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT02894697.

Medium-Term Bioresorbable Scaffold Outcomes Utilising Data From an Australian Clinical Quality Registry

BACKGROUND

Bioresorbable scaffolds (BRS) are a novel technology in coronary intervention. However, recent trials demonstrate higher rates of device failure compared to contemporary drug-eluting stents. This study sought to utilise a clinical quality registry to assess the medium-term safety of the Abbott Absorb BRS (Abbott Vascular, Santa Clara, CA, USA), in an Australian context.

METHODS

A prospective, observational study of 192 BRS percutaneous coronary interventions (PCI) compared to 31,773 non-BRS PCIs entered in the Victorian Cardiac Outcomes Registry from 2013 to 2017. The main outcome measure was patient-oriented composite endpoint (POCE) events comprising all-cause mortality, any myocardial infarction (MI), and any revascularisation.

RESULTS

Bioresorbable scaffolds patients (mean age 61.6±10.5 years, 79% male) were younger, had less comorbidity, less prior PCI, fewer ST elevation myocardial infarction (STEMI) presentations, lower rates of multi-lesion disease and more adjuvant devices compared to non-BRS PCI (all p<0.01). All-cause mortality was 2.1%, myocardial infarction (MI) 2.1%, scaffold thrombosis 3.1% and any revascularisation 14.1% (mean follow-up 27.4±8.9 months). POCE events occurred in 11.5% at 1 year and 16.9% at 2 years, comparable to pooled-trial data. Multivariate predictors of POCE were >1 scaffold used (odds ratio [OR] 4.6, 95% confidence interval [CI] 1.9-11.4, p<0.01) and scaffold diameter ≤2.5 mm (OR 3.3, 95% CI 1.4-7.6, p=0.02). Over 95% guideline adherence was achieved in six of eight patient selection criteria and four of six device deployment criteria.

CONCLUSION

In an Australian setting, BRS were used in non-complex patients. Most guidelines for use were adhered to and outcomes were comparable to pooled trial data. Clinical quality registries are effective in assessing novel treatments and technologies when potential safety concerns develop.

Mechanical properties of the drug-eluting bioresorbable magnesium scaffold compared with polymeric scaffolds and a permanent metallic drug-eluting stent

Objectives

To compare on the bench the physical and mechanical properties of Magmaris, a magnesium bioresorbable scaffold (BRS), with Absorb and DESolve polymeric BRS and a permanent metallic stent.

Background

Understanding the mechanical and physical properties of BRS is crucial for appropriate implantation and postdilatation.

Methods

Testing was performed in fluid at 37°C and in silicone bifurcation phantoms with a 30° angle between main branch (MB) and side branch.

Results

The 3.0‐mm Magmaris BRS did not fracture after MB postdilatation up to 4.4 mm in contrast to the Absorb where the safe postdilatation diameter was 3.7 mm. For dilatation through stent cells, there were no Magmaris fractures with 3.0‐mm noncompliant (NC) balloons inflated to nominal pressure. Mini‐kissing balloon postdilatation with two 3.0‐mm NC balloons up to 17 atm was without fracture except for an outlier. Longitudinal and radial strengths were similar for Magmaris and Absorb BRS. The crossing profile for the Magmaris was larger than other devices. Recoil 120 min after deployment was the greatest for Magmaris but 120 min after 3.5 mm postdilatation all devices had similar diameters.

Conclusions

The Magmaris BRS was more resistant to strut fracture than Absorb. It had a larger crossing profile than other devices and similar radial and longitudinal strengths to Absorb. While recoil after deployment was greater with Magmaris, 120 min after 3.5 mm postdilatation all devices had similar diameters.

A manufacturing and annealing protocol to develop a cold-sprayed Fe-316L stainless steel biodegradable stenting material

Biodegradable stents show promise to revolutionize coronary artery disease treatment. Its successful implementation in the global market remains limited due to the constraints of current generation biodegradable materials. Cold gas dynamic spraying (CGDS) has been proposed as a manufacturing approach to fabricate a metallic biodegradable amalgamate for stent application. Iron and 316L stainless steel powders are combined in a 4:1 ratio to create a novel biomaterial through cold spray. Cold spray processing however, produces a coating in a work hardened state, with limited ductility, which is a critical mechanical property in stent design. To this end, the influence of annealing temperature on the mechanical and corrosion performances of the proposed Fe-316L amalgamate is investigated. It was found that annealing at 1300 °C yielded a complex material microstructure, with an ultimate tensile strength of approximately 280 MPa and ductility of 23%. The static corrosion rate determined at this annealing temperature was equal to 0.22 mg cm^-2 day^-1, with multiple corrosion species identified within the degradation layers. Precipitates were observed throughout the microstructure, which appeared to accelerate the overall corrosion behaviour. It was shown that cold-sprayed Fe-316L has significant potential to be implemented in a clinical setting. STATEMENT OF SIGNIFICANCE: Biodegradable stents have potential to significantly improve treatment of coronary artery disease by decreasing or potentially eliminating late-term complications, including stent fracture and in-stent restenosis. Current generation polymer biodegradable stents have led to poorer patient outcomes in comparison to drug-eluting stents, however, and it is evident that metallic biomaterials are required, which have increased strength. To this end, a novel iron and stainless steel 316L biomaterial is proposed, fabricated through cold-gas dynamic spraying. This study analyses the effect of annealing on the Fe-316L biomaterial through corrosion, mechanical, and microstructural investigations. The quantitative data presented in this work suggests that Fe-316L, in its annealed condition, has the mechanical and corrosion properties necessary for biodegradable stent application.

Very Late Scaffold Thrombosis after Everolimus-Eluting Bioresorbable Scaffold Implantation in Patients with Unremarkable Interim Surveillance Angiography

PURPOSE

Everolimus-eluting bioresorbable scaffolds (BRS) demonstrated an increased risk of very late scaffold thrombosis (VLScT) in comparison with conventional drug-eluting stents. However, characterization of VLScT cases remains scant and the role of interim angiographic surveillance in identifying patients at risk of VLScT is unclear. We therefore set out to identify angiographic predictors of VLScT in our present case series.

METHODS

We analyzed a series of consecutive patients with VLScT presenting to two centers in Munich, Germany. Of interest, all patients had undergone interim planned surveillance angiography. Angiographic films were collected and reviewed and quantitative coronary angiography analysis was done at a core laboratory. Optical coherence tomography (OCT) images at presentation with VLScT were analyzed in patients with available data.

RESULTS

Nine patients presented with 10 VLScT events. Mean age was 62.6 years. Surveillance angiography (between 159 and 476 days) were unremarkable in all cases. Time from index intervention to VLScT ranged from 393 to 1494 days. Nine of 10 events occurred after discontinuation of dual antiplatelet therapy. Four patients underwent OCT. The dominant finding at the time of VLScT was scaffold discontinuity.

CONCLUSIONS

In a series of patients with VLScT after treatment with BRS, routine interim surveillance angiography was available in all patients and failed to identify features predictive of subsequent adverse events.

A novel braided biodegradable stent for use in congenital heart disease: Short-term results in porcine iliac artery

To evaluate the properties and efficacy of a novel braided biodegradable stent (BBS) consisting of poly (p-dioxanone) (PPDO) and polycaprolactone (PCL) for usage in children with congenital cardiovascular diseases. PCL/PPDO composite filaments were fabricated by coating PCL layers onto PPDO filaments, which were fused with PPDO monofilaments to form the BBS. Physical properties of BBSs including elastic recovery rate, deformation rate, and mechanical characteristics with adjunctive post-dilation were evaluated by radial force-tests. Ten BBS stents and 10 metallic wall stents (WS) as controls were implanted into the common carotid arteries of 10 pigs and angiography as well as histological examinations were performed 4 and 8 weeks after implantation. An 8 mm BBS with adjunctive post-dilation had the best morphological retention and dimension stability being similar to an 8 mm WS. Luminal gain percentages of BBS and WS immediately, 4 weeks and 8 weeks after implantation were 20.44 ± 2.82% and 27.08 ± 0.88%, 12.34 ± 0.18% and 17.32 ± 8.24%, as well as -1.76 ± 2.45% and - 0.98 ± 3.23%. Luminal areas, internal elastic laminas, neointimal areas, neointimal thicknesses, and area stenosis were not significantly different at 4 weeks and 8 weeks after implantation. Injury and inflammation were similar in both groups and no malposition, thrombosis or dissection occurred. BBS with adjunctive post-dilation showed good physical properties and mechanical stability noninferior to WS. In vivo evaluations showed that a BBS with post-ballooning had similar short-term outcomes as a WS. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1667-1677, 2019.

Intracoronary Optical Coherence Tomography 2018: Current Status and Future Directions

The advent of intravascular imaging has been a significant advancement in visualization of coronary arteries, particularly with optical coherence tomography (OCT) that allows for high-resolution imaging of intraluminal and transmural coronary structures. Accumulating data support a clinical role for OCT in a multitude of clinical scenarios, including assessing the natural history of atherosclerosis and modulating effects of therapies, mechanisms of acute coronary syndromes, mechanistic insights into the effects of novel interventional devices, and optimization of percutaneous coronary intervention. In this state-of-the-art review, we provide an overview of the published data on the clinical utility of OCT, highlighting the areas that need further investigation and the current barriers for further adoption of OCT in interventional cardiology practice.

In vitro mechanical behavior and in vivo healing response of a novel thin-strut ultrahigh molecular weight poly-l-lactic acid sirolimus-eluting bioresorbable coronary scaffold in normal swine

BACKGROUND

New generation bioresorbable scaffolds (BRS) promise to improve the outcomes of current generation BRS technologies by decreasing wall thickness while maintaining structural strength. This study aimed to compare the biomechanical behavior and vascular healing profile of a novel thin-walled (98 μm) sirolimus-eluting ultrahigh molecular weight BRS (Magnitude, Amaranth Medical) to the Absorb everolimus-eluting bioresorbable vascular scaffold (Abbott Vascular).

METHODS AND RESULTS

In vitro biomechanical testing showed lower number of fractures on accelerated cycle testing over time (at 21K cycles = 20.0 [19.0-21.0] in Absorb versus 0.0 [0.0-1.0] in Magnitude-BRS). Either Magnitude (n = 43) or Absorb (n = 22) was implanted in 65 coronary segments of 22 swine. Scaffold strut's coverage was evaluated using serial optical coherence tomography (OCT) analysis. At 14 days, Magnitude-BRS demonstrated a higher percentage of embedded struts (97.7% [95.3, 100.0] compared to Absorb (57.2% [48.0, 76.0], p = 0.003) and lower percentage of uncovered struts (0.0% [0.0, 0.0] versus Absorb 5.5% [2.6, 7.7], p = 0.02). Also, it showed a lower percent late recoil (-1.02% [-4.11, 3.21] versus 4.42% [-1.10, 8.74], p = 0.04) at 28 days. Histopathology revealed comparable neointimal proliferation and vascular healing responses between two devices up to 180 days.

CONCLUSION

A new generation thin walled (98-μm) Magnitude-BRS displayed a promising biomechanical behavior and strut healing profile compared to Absorb at the experimental level. This new generation BRS platform has the potential to improve the clinical outcomes shown by the current generation BRS.

Routine use of optical coherence tomography in bioresorbable vascular scaffold implantation: insights on technique optimization and long-term outcomes

BACKGROUND

Data from prior studies have shown increased risk of adverse outcomes with bioresorbable vascular scaffolds (BVS) compared with drug-eluting stents.

OBJECTIVE

The objective of this study was to study the long-term outcomes with routine use of optical coherence tomography (OCT) for optimization of BVS implantation.

PATIENTS AND METHODS

Clinical, procedural, and outcome data were collected for all patients who received ABSORB BVS between February 2014 and March 2016 in our tertiary center (n=86). Preimplantation and postimplantation OCT was performed in all cases. Outcomes of interest included acute device success and long-term clinical outcomes including cardiac mortality, target vessel myocardial infarction, ischemia-driven target lesion revascularization, and scaffold thrombosis.

RESULTS

A total of 86 patients were included (106 lesions, 115 BVS implanted). Mean age was 59.5±10.9 years, with 66% men. Mean lesion length was 25.2±15.6 mm and mean reference vessel diameter was 3.42±0.45 mm. Type B2/C accounted for 40% of the lesions. All scaffold implantations followed the predilation, proper sizing, and postdilation strategy. Of the 115 scaffolds analyzed, 11 (9.5%) required further intervention based on prespecified OCT endpoints. On multivariate regression analysis, complex coronary lesion (type B2/C) was the single independent predictor of OCT use in scaffold optimization (odds ratio=6.3, 95% confidence interval: 1.3-7.8, P=0.02). At a mean follow-up duration of 31±7.1 months, no cases of cardiac mortality, target vessel myocardial infarction, ischemia-driven target lesion revascularization, or scaffold thrombosis were reported.

CONCLUSION

Operators may consider OCT use for optimization of BVS implantation particularly in patients with complex coronary lesions.

Clinical results of bioresorbable drug-eluting scaffolds in short and long coronary artery lesions using the PSP technique

BACKGROUND

Data on bioresorbable vascular scaffolds (BVS) for the treatment of long lesions are limited. We studied the use of BVS-Absorb in routine clinical practice and compared the outcome of long lesions with short lesions. Implantation of drug-eluting scaffolds without PSP-technique (predilation, proper sizing and postdilation) is associated with an increased thrombotic risk. We compared the long-term outcome up to 36 months of patients with short (< 20 mm) and long (≥20 mm) coronary artery lesions after implantation of bioresorbable vascular scaffolds (BVS) via PSP-technique.

METHODS

Three hundred twenty-six patients with 424 lesions were enrolled in this prospective study and underwent percutaneous coronary intervention with the Absorb BVS. Clinical follow-up was scheduled after 12, 24 and 36 months. In all lesions the PSP-technique was used. The device oriented composite endpoint (DOCE) was defined as cardiac death, myocardial infarction (MI) not clearly related to a non-target vessel and target lesion revascularization (TLR).

RESULTS

Kaplan-Meier estimates for DOCE after 12 months were 2.63% for short lesions and 8.09% for long lesions (p = 0.0131), 5.51% vs. 11.35% (p = 0.0503) after 24 months and 8.00% vs. 18.00% (p = 0.0264) after 36 months of clinical follow-up. Kaplan-Meier estimates for TLR after 12 months were 1.46% for short and 7.69% for long lesions (p = 0.0012), 2.06% vs. 8.75% after 24 months (p = 0.0027) and 4.96% vs. 9.59% after 36 months of follow-up (p = 0.0109). Scaffold thrombosis rates were low.

CONCLUSIONS

In long lesions compared to short ones the bioresorbable scaffold Absorb implanted with the proper PSP technique Absorb has significant higher rates of DOCE.

THE LEVEL OF EVIDENCE

Is 3 (non-random sample).

Early and long-term outcomes of bioresorbable vascular scaffolds in the treatment of patients with coronary artery disease in real-world clinical practice - insights from the ZABRZE-BVS registry

Introduction

Randomized trials have proven the feasibility and safety of the bioresorbable vascular scaffold (BVS) in selected populations of patients. Data concerning the results of BVS in “real-world” registries with an appropriate sample size are limited.

Aim

Assessment of early- and long-term outcomes of patients undergoing bioresorbable scaffold implantation in an all-comers population of the ZABRZE-BVS registry.

Material and methods

The ZABRZE-BVS registry is a prospective registry including consecutive patients treated in the period 2013–2016 with the intention to implant a BVS (ABSORB, Abbott Vascular, Santa Clara, California). The primary endpoint was occurrence of the 12- and 24-month device-oriented composite endpoint (DoCE) defined as cardiac death, target-vessel myocardial infarction (TV-MI) or target lesion revascularization (TLR). The secondary endpoint includes occurrence of patient-oriented composite endpoint (PoCE) at 12 and 24 months, device (lesion basis) and procedural success (patient basis).

Results

A total of 456 patients during 467 procedures received 588 scaffolds in 563 lesions. Of note, 25.4% of patients presented with diabetes mellitus and 62.3% had an acute coronary syndrome. In QCA analysis, 78.7% of patients had type B2/C lesions, minimal lumen diameter was 0.78 ±0.54 mm, whereas post-procedural acute lumen gain was 1.61 ±0.61 mm. Median follow-up was 781 days. The cumulative rate of DoCE was 6.7% at 12 months and 12.2% at 24 months. Rates of 12- and 24-month PoCE were 12.4% and 20.1%, respectively. The percentage of device success was 98.7%, while the procedural success rate was 96.9%.

Conclusions

The Absorb BVS was successfully and safely implanted in an unselected group of patients. Scaffold thrombosis developed predominantly in patients with acute coronary syndrome (ACS).

"The Unpredictable ABSORB" - Very Late Stent Thrombosis of Bioresorbable Vascular Scaffold

Bioresorbable vascular scaffolds represent the next revolution in stent technology. They serve the dual purpose of antiproliferative drug delivery to vascular lumen like a drug-eluting stents (DES) as well as phased strut resorption over time leading to virtual elimination of stent thrombosis. The ABSORB GT-1 stent was the prototype bioresrbable vascular scaffold with maximum clinical experience and initial promising results. However, reports of stent thrombosis emerged with ABSORB too. Although the use of intracoronary imaging and proper implantation technique has the potential to reduce stent thrombosis rates, the device has been withdrawn from the market for now. We report a case of late stent thrombosis with ABSORB which was managed with DES-supported intracoronary imaging.

Effect of working environment and procedural strategies on mechanical performance of bioresorbable vascular scaffolds

Polymeric bioresorbable scaffolds (BRS), at their early stages of invention, were considered as a promising revolution in interventional cardiology. However, they failed dramatically compared to metal stents showing substantially higher incidence of device failure and clinical events, especially thrombosis. One problem is that use of paradigms inherited from metal stents ignores dependency of polymer material properties on working environment and manufacturing/deployment steps. Unlike metals, polymeric material characterization experiments cannot be considered identical under dry and submerged conditions at varying rates of operation. We demonstrated different material behaviors associated with variable testing environment and parameters. We, then, have employed extracted material models, which are verified by computational methods, to assess the performance of a full-scale BRS in different working condition and under varying procedural strategies. Our results confirm the accepted notion that slower rate of crimping and inflation can potentially reduce stress concentrations and thus reduce localized damages. However, we reveal that using a universal set of material properties derived from a benchtop experiment conducted regardless of working environment and procedural variability may lead to a significant error in estimation of stress-induced damages and overestimation of benefits procedural updates might offer. We conclude that, for polymeric devices, microstructural damages and localized loss of structural integrity should complement former macroscopic performance-assessment measures (fracture and recoil). Though, to precisely capture localized stress concentration and microstructural damages, context-related testing environment and clinically-relevant procedural scenarios should be devised in preliminary experiments of polymeric resorbable devices to enhance their efficacy and avoid unpredicted clinical events. STATEMENT OF SIGNIFICANCE: Bioresorbable scaffolds (BRS) with the hope to become the next cardiovascular interventional revolution failed in comparison to metal stents. When BRS were characterized using methods for metal stents, designers were misled to seek problem sources at erroneous timeframe and use inefficient indicators, and thus no signal of concern emerged. We demonstrated fundamental flaws associated with applying a universal set of material properties to study device performances in different phases of manufacturing/implantation, and these may be responsible for failure in predicting performance in first-generation BRS. We introduced new criterion for the assessment of structural integrity and device efficacy in next-generation BRS, and indeed all devices using polymeric materials which evolve with the environment they reside in.

Long-term follow-up of BVS from a prospective multicenter registry: Impact of a dedicated implantation technique on clinical outcomes

OBJECTIVES

The aim of this study was to evaluate the impact of a consistent and dedicated implantation strategy on long-term outcomes after implantation of bioresorbable vascular scaffold (BVS) in a real-world cohort of patients with a high prevalence of complex lesions.

BACKGROUND

Bioresorbable vascular scaffolds may result in a reduced incidence of late and very-late scaffold thrombosis (ScT) after the complete reabsorption of the scaffold, but this hypothesis is hampered by data from RCTs that showed a higher than expected incidence of late events. However, these studies did not adopt a dedicated implantation technique, that proved to be fundamental in reducing the incidence of adverse events.

METHODS

573 consecutive patients (912 lesions) treated with bioresorbable scaffolds between May 2012 and December 2014 were enrolled in 3 high-volume centers that used a dedicated implantation strategy from the beginning. Primary endpoints were target-lesion failure (TLF) and definite and probable ScT. Secondary endpoints included myocardial infarction, target-lesion and target-vessel revascularization.

RESULTS

The registry enrolled a high complexity subset of lesions (69.4% of type B2 or C lesions; 10.3% of severe calcific lesions; 26.1% of bifurcations). Predilatation was performed in almost all cases (99.2%); intracoronary imaging was liberally adopted (37.3%). Mean scaffold length was 42.9 ± 27.4 mm per patient, and post-dilation with a 1:1 high-pressure (22 ± 3.5 atm) balloon was performed in 99.9% of lesions. Median follow-up (available for 98.6% of patients) was 981 days (IQR 802-1133). Overall incidence of ScT was reassuringly low: three thrombotic events occurred during the first year (0.5%), while only one event ensued in the second year of follow-up, and ScT rate remained stable thereafter up to the fourth year (0.7%). Cumulative TLF rates at 1, 2, 3 and 4 years were 3.0%, 6.0%, 7.8% and 12.2%.

CONCLUSIONS

These long-term results from a complex "real-world" population appear to be reassuring as regards to the incidence of ScT and TLF when BVS are implanted by experienced operators with a dedicated implantation technique.

Blinded outcomes and angina assessment of coronary bioresorbable scaffolds: 30-day and 1-year results from the ABSORB IV randomised trial

BACKGROUND

Previous studies showed more adverse events with coronary bioresorbable vascular scaffolds (BVS) than with metallic drug-eluting stents (DES), although in one randomised trial angina was reduced with BVS. However, these early studies were unmasked, lesions smaller than intended for the scaffold were frequently enrolled, implantation technique was suboptimal, and patients with myocardial infarction, in whom BVS might be well suited, were excluded.

METHODS

In the active-controlled, blinded, multicentre, randomised ABSORB IV trial, patients with stable coronary artery disease or acute coronary syndromes aged 18 years or older were recruited from 147 hospitals in five countries (the USA, Germany, Australia, Singapore, and Canada). Enrolled patients were randomly assigned (1:1) to receive polymeric everolimus-eluting BVS (Absorb; Abbott Vascular, Santa Clara, CA, USA) with optimised implantation technique or cobalt-chromium everolimus-eluting stents (EES; Xience; Abbott Vascular, Santa Clara, CA, USA). Randomisation was stratified by diabetic status, whether patients would have been eligible for enrolment in the previous ABSORB III trial, and site. Patients and clinical assessors were masked to randomisation. The primary endpoint was target lesion failure (cardiac death, target vessel myocardial infarction, or ischaemia-driven target lesion revascularisation) at 30 days, tested for non-inferiority with a 2·9% margin for the risk difference. Analysis was by intention to treat. The trial is registered with ClinicalTrials.gov, number NCT02173379, and is closed to accrual.

FINDINGS

Between Aug 15, 2014, and March 31, 2017, we screened 18 722 patients for eligibility, 2604 of whom were enrolled. 1296 patients were assigned to BVS, and 1308 patients were assigned to EES. Follow-up data at 30 days and 1 year, respectively, were available for 1288 and 1254 patients with BVS and for 1303 and 1272 patients with EES. Biomarker-positive acute coronary syndromes were present in 622 (24%) of 2602 patients, and, by angiographic core laboratory analysis, 78 (3%) of 2893 of lesions were in very small vessels. Target lesion failure at 30 days occurred in 64 (5·0%) patients assigned to BVS and 48 (3·7%) patients assigned to EES (difference 1·3%, upper 97·5% confidence limit 2·89; one-sided p_{non-inferiority}=0·0244). Target lesion failure at 1 year occurred in 98 (7·8%) patients assigned to BVS and 82 (6·4%) patients assigned to EES (difference 1·4%, upper 97·5% confidence limit 3·4; one-sided p_{non-inferiority}=0·0006). Angina, adjudicated by a central events committee at 1 year, occurred in 270 (20·3%) patients assigned to BVS and 274 (20·5%) patients assigned to EES (difference -0·3%, 95% CI -3·4% to 2·9%; one-sided p_{non-inferiority}=0·0008; two-sided p_superiority=0·8603). Device thrombosis within 1 year occurred in nine (0·7%) patients assigned to BVS and four (0·3%) patients assigned to EES (p=0·1586).

INTERPRETATION

Polymeric BVS implanted with optimised technique in an expanded patient population resulted in non-inferior 30-day and 1-year rates of target lesion failure and angina compared with metallic DES.

FUNDING

Abbott Vascular.

Relation between bioresorbable scaffold sizing using QCA-Dmax and long-term clinical outcomes in 1,232 patients from three study cohorts (ABSORB Cohort B, ABSORB EXTEND, and ABSORB II)

AIMS

This study sought to investigate the long-term clinical outcomes related to scaffold sizing based on quantitative coronary angiography.

METHODS AND RESULTS

A total of 1,248 patients who received Absorb bioresorbable scaffolds in the ABSORB Cohort B, ABSORB EXTEND, and ABSORB II trials were included in the analysis. The incidence of MACE (a composite of cardiac death, any myocardial infarction [MI], and ischaemia-driven target lesion revascularisation [ID-TLR]) was analysed according to the Dmax subclassification of oversized scaffold group versus non-oversized (any undersize) scaffold group. At three years, event rates were similar in both groups in MACE (9.4% vs. 9.8%, p=0.847), target vessel MI (5.2% vs. 4.8%, p=0.795), and ID-TLR (4.8% vs. 5.8%, p=0.445). Landmark analysis after one year showed that the non-oversized scaffold group had higher rates of MACE (3.2% vs. 6.9%, log-rank p=0.004), target vessel MI (0.7% vs. 2.7%, log-rank p=0.007), and ID-TLR (2.5% vs. 4.7%, log-rank p=0.041).

CONCLUSIONS

Implantation of an undersized scaffold was associated with a higher risk of MACE between one and three years, while in the previous report an oversized scaffold was associated with a higher risk of MACE up to one year. This implies different mechanisms for early and late events after scaffold implantation.

Different behaviors of bioresorbable vascular scaffold in different types of calcified lesion: Insights from intravascular imaging

A 55-year-old male underwent percutaneous coronary intervention (PCI) for left anterior descending artery chronic total occlusion. After lesion preparation with non-compliant (NC) balloon, two bioresorbable vascular scaffolds (2.5/28 mm, 3.0/28 mm, Absorb BVS, Abbott Vascular, Santa Clara, CA, USA) were implanted followed by 1:1 sized NC balloon post-dilatation at 20 atm. Final intravascular ultrasound (IVUS) showed acceptable BVS expansion in diffusely calcified lesions. Twenty-one months' follow-up coronary angiography revealed severe restenosis with reocclusion at the distal edge of the distal BVS. After recanalization with a 1.0 mm balloon, optical coherence tomography (OCT) was performed. Quantitative analysis comparing OCT and IVUS at the index procedure demonstrated that minimum scaffold area at follow-up became significantly smaller and with higher eccentricity, suggesting severe recoil at the lesions with thick calcium spot, whereas these changes were not observed at the lesion with relatively thin calcification. The lesions were successfully revascularized with drug-eluting stents and final OCT showed symmetric expansion of metallic stents. Our case demonstrates that different types of calcification can have an impact on BVS expansion and recoil. In calcified lesions, an optimal implantation technique is mandatory to achieve the best possible results, and characterization of calcified lesions with intravascular imaging may be helpful to decide PCI strategy with BVS. <Learning objective: Calcified lesions represent a challenging lesion subset for bioresorbable vascular scaffold (BVS) because of less radial strength of the latter. Quantitative analysis with intravascular imaging demonstrated that different types of calcification can have an impact on BVS expansion and recoil. In calcified lesions, an optimal implantation technique is mandatory to achieve the best possible results, and characterization of calcified lesions with intravascular imaging may be helpful to decide percutaneous coronary intervention strategy with BVS.>.

Three-year clinical outcomes of patients treated with everolimus-eluting bioresorbable vascular scaffolds: Final results of the ABSORB EXTEND trial

BACKGROUND

There is still limited data on the very long term clinical outcomes after ABSORB BRS in daily practice. We sought to evaluate the 3 year-performance of the Absorb bioresorbable vascular scaffolds for the treatment of low/moderate complexity patients enrolled in the ABSORB EXTEND trial.

METHODS

ABSORB EXTEND is a prospective, single-arm, open-label clinical study in which 812 patients were enrolled at 56 sites. This study allowed the treatment of lesions ≤28 mm in length and reference vessel diameter of 2.0-3.8 mm (as assessed by on-line QCA). To determine the independent predictors of MACE, a multivariable logistic regression model was built using a stepwise (forward/backward) procedure.

RESULTS

Average population age was 61 years and 26.5% had diabetes. Most patients had single target lesion (92.4%). Adequate scaffold deployment (PSP) was achieved in 14.2% of the cases. At three years, the composite endpoints of MACE and ischemia-driven target vessel failure were 9.2% and 10.6%, respectively. The cumulative rate of ARC definite/probable thrombosis was 2.2%, with 1.2% of the cases occurring after the 1st year. Independent predictors of MACE were hypertension and the need for "bail out" stent.

CONCLUSION

At three-year follow-up, the use of ABSORB in low/moderate complex PCI was associated with low and acceptable rates of major adverse clinical events, despite the infrequent use of the recommended contemporary scaffold deployment technique. However, scaffold thrombosis rate was higher than reported with current generation of metallic DES. The study is registered on clinicaltrials.gov (unique identifier NCT01023789).