Performance Of Bioresorbable Vascular Scaffold Research Articles

Employing Synchrotron X-ray Scattering and Microscopy to Explore Microstructural Mysteries in Bioresorbable Vascular Scaffolds

Crystal structure and morphology dictate the mechanical, thermal, and degradation properties of poly l-lactide (PLLA), the structural polymer of the first clinically approved bioresorbable vascular scaffolds (BVS). New experimental methods are developed to reveal the underlying mechanisms governing structure formation during the crimping step of the BVS manufacturing process. Our research specifically examines the “U-bends” – the region where the curvature is highest and stress is maximised during crimping, which can potentially lead to failure of the device with dramatic consequences on patient life. A custom-made crimping rig operated at a synchrotron beamline enabled collection of wide- and small-angle X-ray scattering (WAXS/SAXS) to probe local variations of the polymer morphology as a function of position in the crest of multiple U-bends with 5 μm resolution in situ after crimping and expansion. Additionally, polarised light microscopy (PLM) images of these deformed U-bends revealed areas with varying stress distribution developed during crimping and expansion. These variations were dependant on the initial biaxial stretching processing step. The integrated X-ray scattering-microscopy approach offered a comprehensive work-flow for uncovering the intricate relationship between processing conditions and the corresponding spatially-resolved semicrystalline morphology of a BVS. Statement of SignificanceThis research introduces a new method for gaining critical insights into the structural changes that occur during the manufacturing process of bioresorbable vascular scaffolds (BVS). The crimping and expansion of poly l-lactide (PLLA) – the structural material of BVS – are sequential manufacturing steps characterised by highly non-linear deformations at temperature conditions that remain unexplored.By utilising synchrotron X-ray scattering techniques alongside polarised light microscopy, we have developed new experimental methods to uncover the mechanisms governing structure formation during processing. This innovative approach not only deepens our understanding of the relationship between processing conditions and polymer morphology but also establishes the foundation for real-time observation methods during crimping and expansion. By improving the design and performance of BVS, this study has the potential to advance cardiovascular treatments and improve patient safety, making it highly relevant and impactful to both scientific research and clinical applications.

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 SignificanceBioresorbable 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.

Angiographic and Midterm Outcomes of Bioresorbable Vascular Scaffold for Coronary Bifurcation Lesions

Data on the angiographic and clinical performance of bioresorbable vascular scaffolds (BVS) for bifurcation lesions treatment are still limited. Data were examined of 107 patients with at least 1 coronary bifurcation lesion involving a side branch ≥2mm. Angiographic and clinical outcomes were collected. Optical coherence tomography analysis was performed in a subgroup of patients. Between July 2009 and December 2015, 423 patients underwent PCI with Absorb BVS. A total of 110 lesions were identified as bifurcations, of which 24.5% were classified as true bifurcation lesions. Lesion complexity B2/C was 68.1%. Ninety-five out of 110 lesions were treated by provisional stenting technique while 2 stenting strategy was the final approach in 15 lesions. Procedural success of main branch was 100% whereas side-branch impairment at the end of the procedure was 4.5%. The mean follow-up was 21 months with one-third of the patients followed up for at least 2 years. The overall target lesion failure and scaffold/stent thrombosis rate at 1 year was 7.8% and 3.9%, respectively. In conclusion the results of the present analysis suggest the BVS implanted in bifurcations lesions are associated with procedural safety and angiographic success as well as acceptable target lesion failure rate at 1 year.

Clinical outcomes of bioresorbable vascular scaffold to treat all-comer patients. Are patients with acute coronary syndrome better candidates for bioresorbable vascular scaffold?

Scaffold thromboses (ST) and adverse events and have been associated with bioresorbable vascular scaffolds (BVS) at long-term, but their mechanism remains unclear. We sought to evaluate patient and lesion characteristics associated with mid- to long-term outcomes in patients treated with BVS. This is an observational single-center, single-arm, retrospective study evaluating the performance of BVS in an all-comer population, including complex lesions (chronic total occlusions, long lesions), small vessels, and acute coronary syndromes (ACS). From May 2013 to June 2015, we included 482 patients (580 lesions) that were treated with BVS implantation including 71.2% treated for ACS in the present analysis. Mean follow-up period was 816.2 ± 242.6 days. The primary endpoint was device oriented cardiac events (DOCE), defined as a composite of target-lesion revascularization (TLR), ST, target vessel myocardial infarction (TVMI) and cardiac death. Using Kaplan-Meier methods, the DOCE and ST rates at 36 months were 9.4% and 2.3%, respectively. No ST occurred between 2 and 3 years and ST occurred after 3 years, in one patient. Using multivariate analysis, ACS was the only significant predictor of lower rates of DOCE (p = 0.04, HR: 0.47, 95% CI: 0.23-0.96). In this large all-comers real-world cohort, lesions treated with BVS had non-negligible rates of DOCE and ST, in line with previous published randomized trials. The occurrence of very late event was very low after 24 months. ACS patients had lower rates of DOCE.

Impact of postdilatation on performance of bioresorbable vascular scaffolds in patients with acute coronary syndrome compared with everolimus-eluting stents: A propensity score-matched analysis from a multicenter "real-world" registry.

Safety and efficacy of bioresorbable vascular scaffolds (BRS) and the role of postdilatation on outcome in acute coronary syndrome (ACS) patients compared with those of everolimus-eluting stents (EES) remain unknown. The aim of the study is to compare the safety and efficacy of BRS with EES in ACS and to investigate the role of BRS postdilatation. Consecutive ACS patients undergoing BRS implantation in 8 centers were com-pared with those with EES before and after propensity score matching. Major adverse cardiac event (MACE), myocardial infarction, and target lesion revascularization (TLR) were the primary endpoint. Sensitivity analysis was performed according to postdilatation after BRS implantation. We enrolled 303 BRS and 748 EES patients; 215 from each group were com-pared after matching, and 117 (55.2%) BRS patients were treated with postdilatation. After a median follow-up of 24.0 months, MACE rates were higher in BRS patients than in EES patients (9.3% vs. 4.7%, p < 0.001), mainly driven by TLR (6.1% vs. 1.9%, p < 0.001). Stent thrombosis increased in the BRS group (2.8% vs. 0.9%, p = 0.01). How-ever, after sensitivity analysis, MACE rates in BRS patients with postdilatation were signifi-cantly lower than in those without, comparable to EES patients (6.0% vs. 12.6% vs. 4.7%, p < 0.001). The same trend was observed for TLR (3.4% vs. 8.4% vs. 1.9%, p < 0.001). Stent thrombosis rates were higher in both the BRS groups than in EES patients (2.6% vs. 3.2% vs. 0.9%, p = 0.045). Postdilatation appears effective when using BRS in ACS patients. MACE rates are comparable to those of EES, although scaffold thrombosis is not negligible. Randomized prospective studies are required for further investigation.

Clinical Comparison With Short-Term Follow-Up of Bioresorbable Vascular Scaffold Versus Everolimus-Eluting Stent in Primary Percutaneous Coronary Interventions

Objective of this study was to assess the clinical performance of bioresorbable vascular scaffold (BVS) compared to everolimus-eluting stent (EES) in subjects with ST-segment elevation myocardial infarction (STEMI). We included all consecutive patients with STEMI who underwent percutaneous coronary intervention (PCI) with BVS implantation in centers participating to the Italian ABSORB Prospective Registry (BVS-RAI) and PCI with EES in the same centers during the same period. The 2 groups were compared. The primary end point was patient-oriented composite end point (POCE) including cardiac death, myocardial infarction, and target lesion revascularization (TLR) at the longest available follow-up. BVS or EES thrombosis at follow-up was also evaluated. Of the 563 patients with STEMI included, 122 received BVS and 441 EES. Procedural success was obtained in 549 (97.5%) cases without significant differences between the 2 groups (BVS 99.3% vs EES 97.0%, p= 0.2). At a median of 220-day (interquartile range 178 to 369) follow-up, no significant differences were observed in terms of POCE (BVS 4.9% vs EES 7.0%, p= 0.4); death (BVS 0.8%, EES 2.0%, p= 0.4), MI (BVS 4.1%, EES 2.0%, p= 0.2), TLR (BVS 4.1%, EES 4.5%, p= 0.8), device thrombosis (BVS 2.5%, EES 1.4%, p= 0.4). All TLR cases were successfully managed with re-PCI in both groups. A propensity matching of the study populations showed no significant differences regarding POCE at the longest available follow-up (odds ratio 0.53, 0.1 to 4.3). In conclusion, in this direct prospective comparison, BVS was associated with similar clinical results compared to EES in the STEMI setting. Larger and adequately powered randomized trials are needed to fully assess the potential clinical benefit of BVS versus the current standard of care in patients with STEMI.

Feasibility of second-generation bioresorbable vascular scaffold implantation in complex anatomical and clinical scenarios.

BackgroundBioresorbable vascular scaffolds (BVS) have become an emerging tool to treat coronary artery disease. However, the current use of BVS is still widely restricted to stable patients and non-complex lesions. In real-world practice patients are far more complex than those with simple type A lesions and the extended use of BVS to complex lesions and high-risk patients needs to be evaluated. Therefore, we sought to investigate the feasibility and performance of BVS in a broad spectrum of patients.Methods106 patients underwent in total 193 BVS implantations. We assessed the device-related (cardiac death, target vessel myocardial infarction, ischemia-driven target lesion revascularization) and patient-related (all-cause death, any reinfarction and any revascularization) composite outcomes.Results90 % of patients (n = 95) had at least one of the following characteristics: >65 years (35 %), ACS (42 %), tortuous vessels (13 %), calcified (17 %) or thrombotic lesions (12 %), lesions defined as AHA type B2/C (42 %), bifurcations (16 %), chronic total occlusions (9 %) or restenosis (14 %). There was no evidence of significant edge dissection, huge thrombus load or incidence of scaffold dislodgement or scaffold disruption in optical coherence tomography pullbacks. Out of 10,157 struts evaluated within 1,117 cross-sections, 302 were classified as malapposed (2.9 %). During a mean follow-up of 147 ± 119 days the rate of device-related events was 2.0 %, whereas patient-related composite events occurred in 6.1 %.ConclusionsOur results strongly suggest that BVS implantation is feasible in a wide spectrum of patients and complex anatomy of coronary lesions. Long-term outcome of BVS should be further investigated in unrestricted settings in randomized controlled trials.Electronic supplementary materialThe online version of this article (doi:10.1007/s00392-014-0757-4) contains supplementary material, which is available to authorized users.