Direct comparison of bioabsorbable and biodurable polymer everolimus-eluting stent in neointimal stent coverage and in-stent thrombus using high-resolution angioscope

Background/Introduction Although second-generation drug eluting stent (DES) employing biodurable polymer drastically shortened the duration of dual antiplatelet therapy (DAPT), previous reports raised concerns that switching from DAPT to single antiplatelet therapy increased rates of subsequent stent thrombosis with time. Third-generation DES employing bioabsorbable polymer has been introduced so as not to hinder the healing process of the vessel wall, however, at present, both DES with bioabsorbable polymer and those with biodurable polymer are used in parallel. It means there is no conclusive evidence regarding pros and cons of these two types of polymers. Purpose This study aims to clarify how bioabsorbable polymer and biodurable polymer act on the human coronary artery by observing neointimal stent coverage (NIC) and in-stent thrombus by comparing the third-generation DES with bioabsorbable-polymer cobalt-platinum everolimus-eluting stent (BP CoPt-EES), and the second-generation DES with biodurable-polymer cobalt-chromium everolimus-eluting stent (DP CoCr-EES). Methods This is a multicenter observational study including 11 hospitals. We investigated 70 stents (BP CoPt-EES: 40, DP CoCr-EES: 30) of 60 cases, who underwent stent implantation followed by simultaneous observation by coronary angiography, IVUS and angioscopy within 6 to 12 months. For angioscopy, we used a recently available, high-resolution angioscope with a pixel count of 9,000 which realized both stent coverage analysis and planar thrombus detection precisely. Neointimal stent coverage was graded from G0: non coverage to G3: full coverage, and heterogeneity value of neointima was measured as the difference between maximum and minimum NIC grade. Results A strong relationship was observed between NIC grade and in-stent thrombus in all stents (p=0.0011), and between the heterogeneity value and stent thrombus (p=0.012). There was no statistical difference in NIC grade between BP CoPt-EES vs. DP CoCr-EES; grade 0: 0 (0.0%) vs. 2 (6.7%), grade 1: 13 (32.5%) vs. 11 (36.7%), grade 2: 6 (15.0%) vs. 6 (20.0%), grade 3: 21 (52.5%) vs. 11 (36.7%), p=0.17) and neither in the heterogeneity value of neointima (p=0.49). The ratio of stent thrombus did not reach statistical difference; 16 (40.0%) in BP CoPt-EES vs. 17 (56.7%) in DP CoCr-EES (p=0.23). Conclusion The existence of stent thrombus was associated with the neointimal stent coverage. There was no significant difference both in neointimal stent coverage and stent thrombus between bioabsorbable polymer cobalt-platinum EES and biodurable polymer cobalt-chromium EES after 6 to 12 months following stent deployment. FUNDunding Acknowledgement Type of funding sources: Private company. Main funding source(s): Boston Scientific JapanOvalis ltd

Mechanical characterization of hydrolysis effects on the stiffness of bioabsorbable polymeric filaments: An experimental and modeling approach based on a simple constitutive damage model

This manuscript presents an experimental and modeling approach in order to characterize the stiffness loss of bioabsorbable polymer filaments due to hydrolysis. In this regard, bioabsorbable suture yarns (poly(lactic-co-glycolic) acid—PLGA) were chosen as a representative material for the present investigation. The observed mechanical response was characterized by means of a thermodynamically consistent constitutive variational framework. Usually, two different damage variables are assumed to take place in this class of materials: a hydrolytic damage (long-term degradation) and a strain-driven damage (short-term degradation). This work concerns the proposition of a constitutive model that only considers the hydrolytic damage, in which a specific strain energy and a proper dissipation damage potential were tailored to model the tested material. A nonlinear curve fitting procedure based on Particle Swarm Optimization was performed to identify the constitutive parameters. A set of numerical simulations demonstrates the effectiveness of the proposed constitutive model to predict damage-induced creep and damage-induced stress relaxation, behaviors that can be used as design criteria in absorbable implants. The main achieved results show that the proposed constitutive approach leads to a simple but effective model capable to drive the first steps in the design of absorbable biomedical devices. The present variational framework can be extended to study the constitutive response of other bioabsorbable polymers, accounting for viscous and/or plastic behaviors.

Comparative Safety of Bioabsorbable Polymer Everolimus-Eluting, Durable Polymer Everolimus-Eluting, and Durable Polymer Zotarolimus-Eluting Stents in Contemporary Clinical Practice

Background: Uncertainty exists over whether stents commonly used for percutaneous coronary intervention have comparable short- and long-term safety. The objective of this study was to determine the outcomes of patients treated with bioabsorbable polymer everolimus-eluting (BP-EES; Synergy, Boston Scientific), durable polymer everolimus-eluting (DP-EES; XIENCE, Abbott Vascular), or durable polymer zotarolimus-eluting (DP-ZES; Resolute, Medtronic) stents in routine clinical practice. Methods: All percutaneous coronary intervention cases from 48 hospitals performed after the introduction of the BP-EES stent in 2015 until the first quarter of 2018 were included. Propensity-matched multivariable analysis was used to adjust for differences in baseline characteristics and procedural variables. After matching, we performed pair-wise comparisons between DP-EES and BP-EES, DP-EES and DP-ZES, and BP-EES and DP-ZES for in-hospital postpercutaneous coronary intervention outcomes. We also evaluated 2-year postdischarge mortality in a subset of patients who could be matched to Medicare data. Results: During the study period, 53 724 percutaneous coronary intervention cases were performed. A total of 59% of patients were treated with DP-EES stents, 14% with BP-EES stents, and 27% with DP-ZES stents. Although baseline characteristics of patients differed between stent types, these differences were attenuated after matching. In the matched cohort, there was no difference in in-hospital mortality, stent thrombosis, or postprocedural stroke (a falsification end point) between BP-EES, DP-EES, and DP-ZES. After matching, there was no difference in 2-year postdischarge mortality (DP-EES versus BP-EES hazard ratio 0.91, P =0.50; DP-EES versus DP-ZES hazard ratio 1.03, P =0.77; BP-EES versus DP-ZES hazard ratio 1.20, P =0.29). Conclusions: Our data suggest similar risk-adjusted in-hospital outcomes among drug-eluting stent platforms commonly used in clinical practice. The absence of a difference in 2-year mortality between BP-EES, DP-EES, and DP-ZES suggests that stent choice decisions could be made based on other factors, including durability, availability, and cost.