Serial In Vivo Intravascular Ultrasound-Based Echogenicity Changes of Everolimus-Eluting Bioresorbable Vascular Scaffold During the First 12 Months After Implantation

A systematic review and meta-analysis of bioresorbable vascular scaffolds for below-the-knee arterial disease

INTRODUCTION

Different types of bioresorbable vascular scaffolds (BVSs) have been developed and used in below-the-knee (BTK) arterial diseases. This is the first study reviewing and analyzing the literature on BVS treatment for BTK arterial disease.

EVIDENCE ACQUISITION

MEDLINE, Embase, and Cochrane were searched for studies published until October 21, 2019. The search, study selection, quality assessment, and data extraction were performed by 2 authors independently. Articles that studied the treatment of BTK arterial disease by using BVSs were eligible. Exclusion criteria were studies with a variant design (e.g. case reports <5 patients), non-BTK indications for BVS use, and nonhuman studies. Primary endpoint was 12-month primary patency. Secondary endpoints were 12-month freedom from clinically driven target lesion revascularization (CD-TLR), limb salvage, survival, and amputation-free survival (AFS). Study quality was assessed by the Methodological Index for Non-randomized Studies score.

EVIDENCE SYNTHESIS

Five studies representing 155 patients with 160 treated limbs met the inclusion criteria. Pooled 12-month primary patency per limb was 90% (143/160; 95% confidence interval [CI]: 0.84-0.95), freedom from CD-TLR 96% (124/130; 95% CI: 0.91-0.99), limb salvage rate 97% (156/160; 95% CI: 0.94-1.00), survival rate 90% (112/125; 95% CI: 0.82-0.96), and AFS rate 89% (110/125; 95% CI: 0.81-0.94). Subgroup analyses of included Absorb BVS studies showed similar results. All studies were assessed as moderate quality.

CONCLUSIONS

This meta-analysis of case series showed good 12-month patency and clinical results with BVSs for BTK arterial disease, even in patients with multimorbidity and short but complex lesions. These results encourage a revival of this scaffold.

Arterial Remodeling After Bioresorbable Scaffolds and Metallic Stents

BACKGROUND

Although previous observational studies have documented late luminal enlargement and expansive remodeling following implantation of a bioresorbable vascular scaffold (BVS), no comparison with metallic stents has been conducted in a randomized fashion.

OBJECTIVES

This study sought to compare vessel remodeling patterns after either Absorb BVS or Xience metallic drug-eluting stent (DES) implantation (Abbott Vascular, Santa Clara, California) and determine the independent predictors of remodeling.

METHODS

In the ABSORB II randomized trial, 383 lesions (n = 359) were investigated by intravenous ultrasound both post-procedure and at 3-year follow-up. According to vessel and lumen area changes over 3 years, we categorized 9 patterns of vessel remodeling that were beyond the reproducibility of lumen and vessel area measurements.

RESULTS

The relative change in mean vessel area was significantly greater with the BVS compared to the DES (6.7 ± 12.6% vs. 2.9 ± 11.5%; p = 0.003); the relative change in mean lumen area was significantly different between the 2 arms (1.4 ± 19.1% vs. -1.9 ± 10.5%, respectively; p = 0.031). Multivariate analysis indicated that use of the BVS, female sex, balloon-artery ratio >1.25, expansion index ≥0.8, previous percutaneous coronary intervention, and higher level of low-density lipoprotein cholesterol were independent predictors of expansive remodeling. Furthermore, in the BVS arm, necrotic core pre-procedure was an independent determinant of expansive remodeling.

CONCLUSIONS

Expansive vessel wall remodeling was more frequent and intense with the BVS than the metallic DES and could be determined by patient baseline characteristics and periprocedural factors. The clinical effect of the observed lumen and vessel remodeling must be investigated in further large clinical studies to optimize the clinical outcome of patients and lesions treated by bioresorbable scaffolds. (ABSORB II Randomized Controlled Trial; NCT01425281).

Pseudogenes regulate parental gene expression via ceRNA network

The concept of competitive endogenous RNA (ceRNA) was first proposed by Salmena and colleagues. Evidence suggests that pseudogene RNAs can act as a 'sponge' through competitive binding of common miRNA, releasing or attenuating repression through sequestering miRNAs away from parental mRNA. In theory, ceRNAs refer to all transcripts such as mRNA, tRNA, rRNA, long non-coding RNA, pseudogene RNA and circular RNA, because all of them may become the targets of miRNA depending on spatiotemporal situation. As binding of miRNA to the target RNA is not 100% complementary, it is possible that one miRNA can bind to multiple target RNAs and vice versa. All RNAs crosstalk through competitively binding to miRNAvia miRNA response elements (MREs) contained within the RNA sequences, thus forming a complex regulatory network. The ratio of a subset of miRNAs to the corresponding number of MREs determines repression strength on a given mRNA translation or stability. An increase in pseudogene RNA level can sequester miRNA and release repression on the parental gene, leading to an increase in parental gene expression. A massive number of transcripts constitute a complicated network that regulates each other through this proposed mechanism, though some regulatory significance may be mild or even undetectable. It is possible that the regulation of gene and pseudogene expression occurring in this manor involves all RNAs bearing common MREs. In this review, we will primarily discuss how pseudogene transcripts regulate expression of parental genes via ceRNA network and biological significance of regulation.

Bioresorbable scaffold - A magic bullet for the treatment of coronary artery disease?

Today, drug-eluting metal stents are considered the gold standard for interventional treatment of coronary artery disease. While providing inhibition of neointimal hyperplasia, drug-eluting metal stents have many limitations such as the risk of late and very late stent thrombosis, restriction of vascular vasomotion and chronic local inflammatory reaction due to permanent implantation of a 'metallic cage', recognized as a foreign body. Bioresorbable scaffold stents (BRS) are a new solution, which is trying to overcome the limitation of the 'metallic cage'. This structure provides short-term scaffolding of the vessel and then disappears, leaving nothing behind. The purpose of this review is to present the theoretical rationale for the use of BRS and to outline the clinical outcomes associated with their use in terms of data obtained from RCTs, clinical trials, registries and real life use. We have also tried to answer all questions on this intervention based on available data, with a focus on ABSORB BVS (Abbott Vascular, Santa Clara, USA). We consider that this new technology can be the "magic bullet" to treat coronary artery disease.

A 12-month angiographic and optical coherence tomography follow-up after bioresorbable vascular scaffold implantation in patients with ST-segment elevation myocardial infarction

OBJECTIVES

The aim of the study was to evaluate the healing process at 12 months after ABSORB™ bioresorbable vascular scaffold (BVS) implantation in patients with ST-segment elevation myocardial infarction (STEMI).

BACKGROUND

There is currently no data on long-term BVS performance in the acute thrombotic setting. The underlying altered plaque pathomorphology may impact the neointima healing pattern, potentially making it different to that observed in stable coronary artery disease (CAD).

METHODS

We have performed an angiographic and optical coherence tomography (OCT) 12-month follow-up of 19 STEMI patients who were treated with a BVS implantation (23 scaffolds). An independent core laboratory performed a paired analysis of the corresponding frames at baseline and follow-up.

RESULTS

At 12 months, the OCT follow-up showed a decrease in the mean lumen area (8.29 ± 1.53 mm(2) vs. 6.82 ± 1.57 mm(2) , P < 0.001), but no significant change in the mean scaffold area (8.49 ± 1.53 mm(2) vs. 8.90 ± 1.51 mm(2) ). Significant decreases in malapposed strut ratio (4.9 ± 8.65% vs. 0.4 ± 1.55%, P < 0.001) and malapposition area (0.29 ± 0.60 mm(2) 0.08 ± 0.32 mm(2) , P = 0.002) were observed. A nonhomogenous proliferation of neointima was revealed with a symmetry index of 0.15 (0.08-0.27), a mean neointima thickness of 203 μm (183-249) and mean neointima area of 2.07 ± 0.51 mm(2) . The quantitative coronary angiography showed late lumen loss of 0.08 ± 0.23 mm and no significant change in the minimal lumen diameter (P = 0.11). There were no major adverse cardiovascular events (MACE), except for one nontarget vessel revascularization.

CONCLUSIONS

The OCT revealed a favorable healing pattern after BVS implantation in a STEMI population.

Echogenicity as a surrogate for bioresorbable everolimus-eluting scaffold degradation: analysis at 1-, 3-, 6-, 12- 18, 24-, 30-, 36- and 42-month follow-up in a porcine model

The objective of the study is to validate intravascular quantitative echogenicity as a surrogate for molecular weight assessment of poly-l-lactide-acid (PLLA) bioresorbable scaffold (Absorb BVS, Abbott Vascular, Santa Clara, California). We analyzed at 9 time points (from 1- to 42-month follow-up) a population of 40 pigs that received 97 Absorb scaffolds. The treated regions were analyzed by echogenicity using adventitia as reference, and were categorized as more (hyperechogenic or upperechogenic) or less bright (hypoechogenic) than the reference. The volumes of echogenicity categories were correlated with the measurements of molecular weight (Mw) by gel permeation chromatography. Scaffold struts appeared as high echogenic structures. The quantification of grey level intensity in the scaffold-vessel compartment had strong correlation with the scaffold Mw: hyperechogenicity (correlation coefficient = 0.75; P < 0.01), upperechogenicity (correlation coefficient = 0.63; P < 0.01) and hyper + upperechogenicity (correlation coefficient = 0.78; P < 0.01). In the linear regression, the R² for high echogenicity and Mw was 0.57 for the combination of hyper and upper echogenicity. IVUS high intensity grey level quantification is correlated to Absorb BVS residual molecular weight and can be used as a surrogate for the monitoring of the degradation of semi-crystalline polymers scaffolds.

Early outcome after implantation of Absorb bioresorbable drug-eluting scaffolds in patients with acute coronary syndromes

AIMS

The safety of BVS implantation in patients with a high risk for early thrombotic complications has not been studied. We report on the outcomes of patients with acute coronary syndromes (ACS) treated with bioresorbable, everolimus-eluting, vascular scaffolds (BVS).

METHODS AND RESULTS

150 consecutive patients with ACS (194 lesions) treated with BVS between May 2012 and July 2013 were compared with a control group composed of 103 consecutive patients (129 lesions) who underwent everolimus drug-eluting stent (DES) implantation in the same time period. The incidence of major adverse cardiac events (MACE: death, non-fatal myocardial infarction, or reintervention) before discharge, at one month and six months was evaluated. Clinical characteristics and presentation were similar between groups. Procedural characteristics were also similar between groups, except for the use of glycoprotein IIb/IIIa inhibitors (p<0.01). Procedural success was obtained in all but two patients in the BVS group. In-hospital, 30-day and six-month MACE rates were similar between both groups (all p>0.5), with most complications occurring during the first ten days. Definite or probable in-stent/scaffold thrombosis occurred in two BVS patients and one DES patient during the index admission and it occurred in another patient in each group in the first month after BVS/DES implantation. In multivariate analysis, BVS utilisation did not influence the incidence of MACE (p>0.9).

CONCLUSIONS

BVS implantation for patients with ACS is safe, with outcomes comparable with those of drug-eluting metal stents.

Application of ultrasound on monitoring the evolution of the collagen fiber reinforced nHAC/CS composites in vivo

To date, fiber reinforce scaffolds have been largely applied to repair hard and soft tissues. Meanwhile, monitoring the scaffolds for long periods in vivo is recognized as a crucial issue before its wide use. As a consequence, there is a growing need for noninvasive and convenient methods to analyze the implantation remolding process in situ and in real time. In this paper, diagnostic medical ultrasound was used to monitor the in vivo bone formation and degradation process of the novel mineralized collagen fiber reinforced composite which is synthesized by chitosan (CS), nanohydroxyapatite (nHA), and collagen fiber (Col). To observe the impact of cells on bone remodeling process, the scaffolds were planted into the back of the SD rats with and without rat bone mesenchymal stem cells (rBMSCs). Systematic data of scaffolds in vivo was extracted from ultrasound images. Significant consistency between the data from the ultrasound and DXA could be observed (P < 0.05). This indicated that ultrasound may serve as a feasible alternative for noninvasive monitoring the evolution of scaffolds in situ during cell growth.

A nontoxic additive to introduce x-ray contrast into poly(lactic acid). Implications for transient medical implants such as bioresorbable coronary vascular scaffolds

Bioresorbable coronary vascular scaffolds are about to revolutionize the landscape of interventional cardiology. These scaffolds, consisting of a poly(L-lactic acid) interior and a poly(D,L-lactic acid) surface coating, offer a genuine alternative for metallic coronary stents. Perhaps the only remaining drawback is that monitoring during implantation is limited to two X-ray contrast points. Here, a new approach to make the biodegradable scaffolds entirely radiopaque is explored. A new contrast agent is designed and synthesized. This compound is miscible with poly(D,L-lactic acid) matrix, and nontoxic to multiple cell types. Blends of poly(D,L-lactic acid) and the contrast agent are found to be hemocompatible, noncytotoxic, and radiopaque. The data show that it is possible to manufacture fully radiopaque bioresorbable coronary vascular scaffolds. Whole-stent X-ray visibility helps interventionalists ensure that the scaffold deploys completely. This important advantage may translate into improved safety, accuracy, and clinical performance of cardiac stents.

Serial observation of drug-eluting absorbable metal scaffold: multi-imaging modality assessment

BACKGROUND

The drug-eluting absorbable metal scaffold has demonstrated feasibility, safety, and promising clinical and angiographic outcomes at 12 months in human coronary arteries. This study aimed to evaluate the degradation rate and long-term vascular responses to drug-eluting absorbable metal scaffold.

METHODS AND RESULTS

BIOSOLVE-I was a multicenter, single-arm, first-in-man trial assessing the safety and performance of drug-eluting absorbable metal scaffold in 46 patients with coronary artery disease. Patients who underwent serial invasive imaging, such as quantitative coronary angiography, intravascular ultrasound, and optical coherence tomography, at 6 and 12 months were included in this study. From postimplantation to follow-up, arterial curvature and angulation were significantly increased by the degradation process. The greatest increase was seen from postimplantation to 6 months. The systolic-diastolic changes of the curvature and angulation gradually improved throughout the follow-up period. At the site of implantation, vasoconstriction (-10% mean reduction) was observed during the acetylcholine test at 6 months. The average percent hyperechogenicity of the scaffolded segments showed a continuous decrease over time, with the most pronounced changes within the first 6 months (from 22.1±7.0% to 15.8±3.7%; P<0.001). Struts discernible on optical coherence tomography at 6 and 12 months showed full neointimal coverage, with stabilization of the mean scaffold area from 6 to 12 months. Furthermore, the mean neointimal area (1.55±0.51 versus 1.58±0.34 mm(2); P=0.794) remained unchanged from 6 to 12 months.

CONCLUSIONS

This serial analysis of drug-eluting absorbable metal scaffold confirmed the safety and efficacy of this new device, with vasomotion restoration and continued degradation over time demonstrated by multi-invasive imaging modalities.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01168830.

Endothelial-dependent vasomotion in a coronary segment treated by ABSORB everolimus-eluting bioresorbable vascular scaffold system is related to plaque composition at the time of bioresorption of the polymer: indirect finding of vascular reparative therapy?

AIMS

To analyse the vasoreactivity of a coronary segment, previously scaffolded by the ABSORB bioresorbable vascular scaffold (BVS) device, in relationship to its intravascular ultrasound-virtual histology (IVUS-VH) composition and reduction in greyscale echogenicity of the struts. Coronary segments, transiently scaffolded by a polymeric device, may in the long-term recover a normal vasomotor tone. Recovery of a normal endothelial-dependent vasomotion may be enabled by scaffold bioresorption, composition of the underlying tissue, or a combination of both mechanisms.

METHODS AND RESULTS

All patients from the ABSORB Cohort A and B trials, who underwent a vasomotion test and IVUS-VH investigation at 12 and 24 months, were included. Acetylcholine (Ach) and nitroglycerin were used to test either the endothelial-dependent or -independent vasomotion of the treated segment. Changes in polymeric strut echogenicity-a surrogate for bioresorption-IVUS-VH composition of the tissue underneath the scaffold and their relationship with the pharmacologically induced vasomotion were all evaluated. Overall, 26 patients underwent the vasomotion test (18 at 12 and 8 at 24 months). Vasodilatory response to Ach was quantitatively associated with larger reductions over time in polymeric strut echogenicity (y= -0.159x- 6.85; r= -0.781, P< 0.001). Scaffolded segments with vasoconstriction to Ach had larger vessel areas (14.37 ± 2.50 vs. 11.85 ± 2.54 mm(2), P= 0.030), larger plaque burden (57.31 ± 5.96 vs. 49.09 ± 9.10%, P= 0.018), and larger necrotic core (NC) areas [1.39 (+1.14, +1.74) vs. 0.78 mm(2) (+0.20, +0.98), P= 0.006] compared with those with vasodilation.

CONCLUSION

Vasodilatory response to Ach, in coronary segments scaffolded by the ABSORB BVS device, is associated with a reduction in echogenicity of the scaffold over time, and a low amount of NC. In particular, the latter finding resembles the behaviour of a native coronary artery not caged by an intracoronary device.

Everolimus-eluting ABSORB bioresorbable vascular scaffold: present and future perspectives

Everolimus-eluting ABSORB bioresorbable vascular scaffolds represent a novel approach that provides transient vessel support with drug-delivery capability without the long-term limitations of the metallic drug-eluting stents (DESs). The technology has the potential to overcome many of the safety concerns associated with metallic DESs and possibly even convey further clinical benefit. In particular the scaffold is designed for providing a short-term lumen support (up to 6-12 months) and for thereafter being completely bioresorbed, eliminating the permanent caging typical of the metallic DES. The first clinical studies testing this device in a small number of patients have shown very promising results with good clinical outcome up to 5 years' follow-up, highlighting important morphological and functional modifications at the scaffolded segment level, such as late lumen enlargement and recuperation of a normal vasoreactivity. A randomized trial, comparing ABSORB with the Xience Prime stent, will evaluate the efficacy and safety of this device in a wide population.