Bioresorbable Scaffolds for the Management of Coronary Bifurcation Lesions

Corroded iron stent increases fibrin deposition and promotes endothelialization after stenting

Poststent restenosis is caused by insufficient endothelialization and is one of the most serious clinical complications of stenting. We observed a rapid endothelialization rate and increased fibrin deposition on the surfaces of the corroded iron stents. Thus, we hypothesized that corroded iron stents would promote endothelialization by increasing fibrin deposition on rough surfaces. To verify this hypothesis, we conducted an arteriovenous shunt experiment to analyze fibrin deposition in the corroded iron stents. We implanted a corroded iron stent in both the carotid and iliac artery bifurcations to elucidate the effects of fibrin deposition on endothelialization. Co-culture experiments were conducted under dynamic flow conditions to explore the relationship between fibrin deposition and rapid endothelialization. Our findings indicate that, from the generation of corrosion pits, the surface of the corroded iron stent was rough, and numerous fibrils were deposited in the corroded iron stent. Fibrin deposition in corroded iron stents facilitates endothelial cell adhesion and proliferation, which, in turn, promotes endothelialization after stenting. Our study is the first to elucidate the role of iron stent corrosion in endothelialization, pointing to a new direction for preventing clinical complications caused by insufficient endothelialization.

Impact of directional coronary atherectomy followed by drug-coated balloon strategy to avoid the complex stenting for bifurcation lesions

Although the simple single stenting rather than complex double stenting is recommended on percutaneous coronary intervention (PCI) for bifurcation lesions, double stenting cannot always be avoided. We investigated the impact of directional coronary atherectomy (DCA), followed by drug-coated balloon (DCB) treatment to reduce the number of stents and avoid complex stenting in PCI for bifurcation lesions and short-term patency. DCA treatment without stents was attempted for 27 bifurcation lesions in 25 patients, of those, 26 bifurcation lesions in 24 patients were successfully treated and 3-month follow-up angiography and optical coherence tomography (OCT) were performed. Sixteen lesions (59.3%) were related to left main trunk distal bifurcations, and 7 (25.9%) were true bifurcation lesions. Among the true bifurcation lesions, 4 lesions (57.1%) needed 1 stent, and the other 3 lesions (42.9%) needed no stents. Among the non-true bifurcation lesions, 1 lesion (5.0%) needed bailout stent and other lesions (95.0%) needed no stents. According to DCA followed by DCB treatment, the angiographic mean diameter stenosis improved from 65.5 ± 15.0% to 7.8 ± 9.8%, and the mean plaque area in intravascular ultrasound improved from 80.4 ± 10.5% to 39.0 ± 11.5%, respectively. Angiographic and OCT late lumen loss values were 0.2 ± 0.6 mm and 1.4 ± 1.9 mm, respectively. No patient had in-hospital major adverse cardiac events (MACE) and 3-month MACE. In conclusion, compared with standard provisional side branch stenting strategy, DCA followed by DCB treatment might reduce the number of stents, avoid complex stenting for major bifurcation lesions and provide good short-term outcomes.

Clinical presentation does not affect acute mechanical performance of the Novolimus-eluting bioresorbable vascular scaffold as assessed by optical coherence tomography

Introduction

Initial trials of bioresorbable vascular scaffolds (BVS) have mostly excluded patients presenting with acute coronary syndrome (ACS). However, these patients might benefit from a BVS platform, in particular as they are often younger and have been less frequently treated than patients with chronic disease.

Aim

To compare the acute performance of a Novolimus eluting BVS in ACS and non-ACS patients using optical coherence tomography (OCT) in patients presenting with acute or chronic coronary syndrome.

Material and methods

The final OCT pullback of 79 patients (34 with ACS, 45 non-ACS) was analysed at 1-mm intervals. The following indices were calculated: mean and minimal area, residual area stenosis, incomplete strut apposition, tissue prolapse, eccentricity index, symmetry index, strut fracture, and edge dissection.

Results

OCT showed a minimum lumen area (non-ACS vs. ACS) of 6.2 ±2.1 vs. 5.6 ±1.5 mm² (p = 0.21). Mean residual area stenosis was 14.5% vs. 19.5% (p = 0.39). The mean eccentricity index did not differ significantly (0.78 ±0.13 vs. 0.78 ±0.06; p = 0.42). There was a non-significant tendency for more fractures in the non-ACS group (22.2% vs. 5.9%; p = 0.07). Prolapse area was comparable (4.4 ±7.4 mm² vs. 5.2 ±10.9 mm²; p = 0.62).

Conclusions

This is the first study to investigate the acute mechanical performance of a Novolimus-eluting BVS in patients with different clinical presentations using OCT. We found that clinical presentation did not determine acute mechanical performance as assessed by the final OCT pullback. There was evidence of more mechanical complications in terms of fractures and a higher percentage of incomplete strut apposition in the group of patients with chronic coronary syndrome.

A Novel Biodegradable Multilayered Bioengineered Vascular Construct with a Curved Structure and Multi-Branches

Constructing tissue engineered vascular grafts (TEVG) is of great significance for cardiovascular research. However, most of the fabrication techniques are unable to construct TEVG with a bifurcated and curved structure. This paper presents multilayered biodegradable TEVGs with a curved structure and multi-branches. The technique combined 3D printed molds and casting hydrogel and sacrificial material to create vessel-mimicking constructs with customizable structural parameters. Compared with other fabrication methods, the proposed technique can create more native-like 3D geometries. The diameter and wall thickness of the fabricated constructs can be independently controlled, providing a feasible approach for TEVG construction. Enzymatically-crosslinked gelatin was used as the material of the constructs. The mechanical properties and thermostability of the constructs were evaluated. Fluid-structure interaction simulations were conducted to examine the displacement of the construct’s wall when blood flows through it. Human umbilical vein endothelial cells (HUVECs) were seeded on the inner channel of the constructs and cultured for 72 h. The cell morphology was assessed. The results showed that the proposed technique had good application potentials, and will hopefully provide a novel technological approach for constructing integrated vasculature for tissue engineering.

Characteristics and outcome of patients with complex coronary lesions treated with bioresorbable scaffolds: three-year follow-up in a cohort of consecutive patients

AIMS

The safety of bioresorbable scaffolds (BRS) has recently been challenged. However, it is unclear whether outcomes depend on the complexity of the lesion or on the technique used to implant the device. The aim of this study was to report on the outcomes after BRS implantation in complex lesions.

METHODS AND RESULTS

This investigator-initiated, single-centre, single-arm observational study recruited 657 consecutive patients (79% male, 66.7% acute coronary syndrome, age 63±12 years). Three hundred and twenty-two lesions (42.3%) in 297 (45.2%) patients with type B2 or C lesions were classified as the "complex lesions group". Post-procedural residual stenosis was slightly but significantly greater in the complex lesions group (15.7±11.3% vs. 13.5±10.2%, p=0.0109). The median follow-up was 1,076 (762-1,206) days without difference between groups. The Kaplan-Meier rates of early scaffold thrombosis (3.5% vs. 1.1%, p=0.0478, HR 3.03 [1.06-8.70]) and scaffold restenosis (9.9% vs. 9.1%, p=0.0262, HR 2.34 [1.11-4.94]) were higher in patients with complex lesions than in those with simple lesions. Late/very late thrombosis, death, repeat myocardial infarction, or repeat coronary interventions were not different. In patients in whom strict guidelines for implantation were applied, the incidence of thrombosis was reduced by 76% in complex lesions and by 92% in simple ones, such that there were no differences between groups (2.3% vs. 0.5%, p=0.3899). In contrast, the incidence of scaffold restenosis was reduced by 59% and 89%, and a difference between groups persisted (7.0% vs. 1.6%, p=0.0235).

CONCLUSIONS

BRS implantation in complex lesions is, as expected, associated with higher incidence of events as compared to simple ones. The technique used at the time of the implantation, however, reduces the incidence of adverse outcomes.

Branch ostial optimization treatment and optimized provisional t-stenting with polymeric bioresorbable scaffolds: Ex-vivo morphologic and hemodynamic examination

The optimal side-branch (SB) ostium treatment after provisional side-branch scaffolding remains a subject of debate in bioresorbable vascular scaffold (BVS) era. In this study, we evaluated a novel optimized provisional T-stenting technique (OPT) and assessed its feasibility by comparison with T and small protrusion technique (TAP).Two provisional SB scaffolding techniques (OPT, n = 5; TAP, n = 5) were performed using polymeric BVS in a bifurcated phantom. The sequential intermediate snuggling balloon dilation, also called ostial optimal technique, was added to OPT but not TAP to dilate the side-branch ostium while the final snuggling balloon dilation applied for both procedures. Microcomputed tomography (microCT) and optical coherence tomography (OCT) were performed to assess morphology, and computational fluid dynamics (CFD) was performed to assess hemodynamics in the scaffolded bifurcations. Compared with TAP in microCT analysis, OPT created shorter neo-carina length than TAP (0.34 ± 0.10 mm vs 1.02 ± 0.26 mm, P < .01), longer valgus struts length (2.49 ± 0.27 mm vs 1.78 ± 0.33 mm, P < .01) with larger MB ostial area (9.46 ± 0.04 mm vs 8.34 ± 0.09 mm, P < .01). OCT found that OPT significantly decreased the struts mal-apposition (13.20 ± 0.16% vs 1.94 ± 0.54%, P < .01). CFD revealed that OPT generated more favorable flow pattern than TAP, as indicated by less percent (4.68 ± 1.40% vs 8.88 ± 1.21%, P < .01) of low wall shear stress (<0.4 Pa) along the lateral walls.By using BVSs for bifurcation intervention, the sequential intermediate snuggling balloon dilation is feasible for optimizing ostial SB and facilitating subsequent SB scaffolding. Results show OPT is better than TAP for bifurcated morphology and hemodynamics in this ex-vivo study.

Hybrid Percutaneous Coronary Intervention With Bioresorbable Vascular Scaffolds in Combination With Drug-Eluting Stents or Drug-Coated Balloons for Complex Coronary Lesions

Bioresorbable vascular scaffolds (BVS) have become an attractive option in the percutaneous coronary intervention field due to the potential advantages associated with the complete resorption process that occurs within a few years. However, current-generation BVS have several limitations including thicker struts, reduced radial strength, and limited expansion capability when compared with drug-eluting stents (DES). As a result, complex coronary disease often contains BVS-inappropriate/unfavorable segments. This does not necessarily mean that BVS use must be completely avoided, and minimizing the length of permanent metallic caging may still be advantageous. Operators should fully understand the limitations of current BVS, and when to consider a hybrid strategy of BVS in combination with DES or drug-coated balloons.

Contemporary Approach to Coronary Bifurcation Lesion Treatment

Coronary bifurcations are frequent and account for approximately 20% of all percutaneous coronary interventions. Nonetheless, they remain one of the most challenging lesion subsets in interventional cardiology in terms of a lower procedural success rate and increased rates of long-term adverse cardiac events. Provisional side branch stenting should be the default approach in the majority of cases and we propose easily applicable and reproducible stepwise techniques associated with low risk of failure and complications.

Long-term in vivo corrosion behavior, biocompatibility and bioresorption mechanism of a bioresorbable nitrided iron scaffold

Pure iron as a potential bioresorbable material for bioresorbable coronary scaffold has major disadvantages of slow corrosion and bioresorption. However, so far, there are neither quantitative data of long-term in vivo corrosion nor direct experimental evidence for bioresorption of pure iron and its alloys, which are fundamental and vital for developing novel Fe-based alloys overcoming the intrinsic drawbacks of pure iron. This work systemically investigated scaffold performance, long-term in vivo corrosion behavior and biocompatibility of a nitrided iron coronary scaffold and explored its bioresorption mechanism. It was found that the 70μm Fe-based scaffold was superior to a state of the art Co-Cr alloy stent (Xience Prime™) in terms of crossing profile, recoil and radial strength. Mass loss was 76.0±8.5wt% for the nitrided iron scaffold and 44.2±11.4wt% for the pure iron scaffold after 36months implantation in rabbit abdominal aorta (p<0.05). The Fe-based scaffold showed good long-term biocompatibility in both rabbit and porcine model. Its insoluble corrosion products were demonstrated biosafe and could be cleared away by macrophages from in situ to adventitia to be indiscernible by Micro Computed Tomography and probably finally enter the lymphatics and travel to lymph nodes after 53months implantion in porcine coronary artery. The results indicate that the nitrided iron scaffold with further improvements shall be promising for coronary application.

STATEMENT OF SIGNIFICANCE

Pure iron as a potential bioresorbable material has major disadvantages of slow corrosion and bioresorption. However, so far, there are neither quantitative data of long-term in vivo corrosion nor direct experimental evidence for bioresorption of pure iron and its alloys. Only this work systemically investigated long-term in vivo corrosion behavior and biocompatibility of a nitrided iron coronary scaffold up to 53months after implantation and explored its bioresorption mechanism. These are fundamental and vital for developing novel Fe-based alloys overcoming the intrinsic drawbacks of pure iron. Novel testing and section-preparing methods were also provided in this work to facilitate future research and development of novel Fe-based alloy scaffolds.

A hybrid strategy with bioresorbable vascular scaffolds and drug eluting stents for treating complex coronary lesions

BACKGROUND

Due to the inherent limitations of current generation BVSs, complex coronary artery disease often contains BVS unsuitable segments. Our aim was to assess the feasibility of a hybrid approach using bioresorbable vascular scaffolds (BVSs) and drug-eluting stents (DESs) for the treatment of complex coronary artery lesions not suitable for a scaffolding only approach.

METHODS

A retrospective multicenter cohort analysis was performed on patients with complex de novo or in-stent restenosis lesions treated with a hybrid BVS (Absorb BVS, Abbott Vascular, Santa Clara, CA) and DES strategy. The primary endpoint was target lesion failure (TLF) defined as a composite of cardiac death, target-vessel myocardial infarction (MI) and target lesion revascularization (TLR).

RESULTS

A total of 98 patients (105 lesions) were treated with the hybrid strategy. Isolated long lesions in which either proximal or distal reference vessel diameters were not suitable for BVS were an indication in 36.2% (n=38) of cases. In contrast, 28% (n=29) of lesions treated with the hybrid strategy were bifurcations in which the side branch was predominantly treated with DES (n=28). DES bailout after BVS implantation was an indication in 21.9% (n=23 lesions). The rates of type B2/C and long lesions (>28mm) were 95.2% and 74.3% respectively. The mean total BVS and DES lengths implanted were 37.5±24.1mm and 25.0±14.7mm respectively. The rate of TLF in the overall cohort of patients (median follow-up 405days [interquartile range 189-658]) was 11.4% at 1-year. This was primarily driven by TLR (9.5%), with rates of cardiac death and target vessel MI of 2.1% and 1.4% respectively. No cases of definite or probable BVS/DES thrombosis occurred.

CONCLUSION

In conclusion, the use of a hybrid BVS/DES strategy was feasible and associated with acceptable outcomes at 1-year, considering the length and complexity of lesions treated. Further, larger studies with longer follow-up are needed to confirm our findings.