Serial changes of neointimal tissue after everolimus-eluting stent implantation in porcine coronary artery: an optical coherence tomography analysis

A novel polymer-free everolimus-eluting stent with a nitrogen-doped titanium dioxide film inhibits restenosis and thrombosis in a swine coronary model

BACKGROUND

Short-term outcomes regarding the safety and efficacy of a polymer-free everolimus-eluting stent (EES) with a nitrogen-doped titanium dioxide (N-TiO₂) film in a swine coronary model have been reported. However, the long-term results of the use of this type of stent have not yet been evaluated or compared to those of other polymer-free coronary stents. Therefore, this study aimed to determine the mid- to long-term safety and efficacy of a polymer-free EES with an N-TiO₂ film in a swine coronary model.

METHODS

Polymer-free EES with N-TiO₂ films (n = 30) and polymer-free sirolimus-eluting stents (SES; n = 30) were implanted in 30 pigs. Quantitative coronary analysis and optical coherence tomography were conducted immediately and at 1 (quantitative coronary analysis only), 3, and 6 months after stenting. Histopathologic examinations were performed at 1, 3, and 6 months after stenting.

RESULTS

The polymer-free EES group had a lower percentage of neointimal growth than the polymer-free SES group at 3 months (22.5% ± 11.4% vs. 32.1% ± 12.3%; p < 0.001). The polymer-free EES group had a lower fibrin score than the polymer-free SES group at 1 month (1.9 ± 0.45 vs. 2.5 ± 0.54; p = 0.001). The re-endothelialization rates were similar between groups. The polymer-free EES group had a lower percentage of the area of stenosis than the polymer-free SES group throughout the follow-up period.

CONCLUSIONS

The novel polymer-free EES with an N-TiO₂ film has superior safety and efficacy than the polymer-free SES at the 6-month follow-up in a swine model.

Balloons and Stents and Scaffolds: Preclinical Evaluation of Interventional Devices for Occlusive Arterial Disease

Atherosclerosis places a significant burden on humankind; it is the leading cause of mortality globally, and for those living with atherosclerosis, it can significantly impact quality of life. Fortunately, treatment advances have effectively reduced the morbidity and mortality related to atherosclerosis, with one such modality being percutaneous intervention (PCI) to open occluded arteries. Over the 40-year history of PCI, preclinical models have played a critical role in demonstrating proof of concept, characterizing the in vivo behavior (pharmacokinetics, degradation) and providing a reasonable assurance of biologic safety of interventional devices before entering into clinical trials. Further, preclinical models may provide insight into the potential efficacy of these devices with the appropriate study design and end points. While several species have been used in the evaluation of interventional devices, the porcine model has been the principal model used in the evaluation of safety of devices for both coronary and endovascular treatments. This article reviews the fundamentals of permanent stents, transient scaffolds, and drug-coated balloons and the models, objectives, and methods used in their preclinical evaluation.

An optical coherence tomography study of neointimal morphology and strut coverage at different time intervals from implantation of biodegradable polymer-coated sirolimus-eluting stents

OBJECTIVES

The aim of the study was to capture the evolution of neointima after implantation of a biodegradable polymer-coated, sirolimus-eluting, cobalt-chromium coronary stent system (BP-DES).

BACKGROUND

Optical coherence tomography (OCT) suggests that in-stent neointimal morphology influences clinical outcomes after DES implantation.

METHODS

Sixty patients treated with single BP-DES implantation were examined by quantitative coronary angiography (QCA) and OCT at 3, 6, and 12-month follow-up.

RESULTS

Median late lumen loss by QCA (mm) was 0.04 (IQR 0, 0.08), 0.17 (IQR 0, 0.32), and 0.14 (IQR 0.07, 0.31) at 3, 6, and 12-month follow-up respectively (P = 0.03). OCT cross-section multilevel analysis showed uncovered struts in 3.90%, 1.78%, and 0.02% of struts respectively (P = 0.03). The corresponding malapposition rates were 0.12%, 0.04%, and 0%. Lipid-rich neointima was observed only at 12-month follow-up in one restenotic lesion (0.77% cross-sections) that was accountable for the only target vessel revascularization. The homogeneous pattern was prevalent at all three time points, but its incidence displayed an upward trend (3 months: 59%; 6 months: 71%; 12 months: 88%) despite no difference in neointimal volume between 6 and 12 months. Conversely, a trend could be observed of decreasing incidence of heterogeneous pattern as the follow-up length increased.

CONCLUSIONS

In this study of a single-type BP-DES, the majority of stent struts were covered within 3 months from implantation. While the quantitative neointimal accumulation plateaued at 6 months with no further significant increase beyond 6 months, the neointima continued to evolve qualitatively and mature along with better strut coverage between 6 and 12 months after implantation.