Impact of underlying plaque type on strut coverage in the early phase after drug-eluting stent implantation

Plaque burden is associated with minimal intimal coverage following drug-eluting stent implantation in an adult familial hypercholesterolemia swine model

Safety and efficacy of coronary drug-eluting stents (DES) are often preclinically tested using healthy or minimally diseased swine. These generally show significant fibrotic neointima at follow-up, while in patients, incomplete healing is often observed. The aim of this study was to investigate neointima responses to DES in swine with significant coronary atherosclerosis. Adult familial hypercholesterolemic swine (n = 6) received a high fat diet to develop atherosclerosis. Serial OCT was performed before, directly after, and 28 days after DES implantation (n = 14 stents). Lumen, stent and plaque area, uncovered struts, neointima thickness and neointima type were analyzed for each frame and averaged per stent. Histology was performed to show differences in coronary atherosclerosis. A range of plaque size and severity was found, from healthy segments to lipid-rich plaques. Accordingly, neointima responses ranged from uncovered struts, to minimal neointima, to fibrotic neointima. Lower plaque burden resulted in a fibrotic neointima at follow-up, reminiscent of minimally diseased swine coronary models. In contrast, higher plaque burden resulted in minimal neointima and more uncovered struts at follow-up, similarly to patients' responses. The presence of lipid-rich plaques resulted in more uncovered struts, which underscores the importance of advanced disease when performing safety and efficacy testing of DES.

An Implantable Artificial Atherosclerotic Plaque as a Novel Approach for Drug Transport Studies on Drug-Eluting Stents

Atherosclerotic arteries are commonly treated using drug-eluting stents (DES). However, it remains unclear whether and how the properties of atherosclerotic plaque affect drug transport in the arterial wall. A limitation of the currently used atherosclerotic animal models to study arterial drug distribution is the unpredictability of plaque size, composition, and location. In the present study, the aim is to create an artificial atherosclerotic plaque-of reproducible and controllable complexity and implantable at specific locations-to enable systematic studies on transport phenomena of drugs in stented atherosclerosis-mimicking arteries. For this purpose, mixtures of relevant lipids at concentrations mimicking atherosclerotic plaque are incorporated in gelatin/alginate hydrogels. Lipid-free (control) and lipid-rich hydrogels (artificial plaque) are created, mounted on DES and successfully implanted in porcine coronary arteries ex-vivo. Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) is used to measure local drug distribution in the arterial wall behind the prepared hydrogels, showing that the lipid-rich hydrogel significantly hampers drug transport as compared to the lipid-free hydrogel. This observation confirms the importance of studying drug transport phenomena in the presence of lipids and of having an experimental model in which lipids and other plaque constituents can be precisely controlled and systematically studied.

Using Optical Coherence Tomography to Identify Lipid and Its Impact on Interventions and Clinical Events - A Scoping Review

BACKGROUND

Optical coherence tomographic (OCT) imaging has enabled identification of lipid, with increasing interest in how it may affect coronary interventions and clinical outcomes. This review summarizes the available evidence around OCT identification of lipid and its effect on interventions, clinical events, and the natural history of coronary disease.

METHODS AND RESULTS

We conducted a scoping review using the Medline, HealthStar, and Embase databases for articles published between 1996 and 2021. We screened 1,194 articles and identified 51 for inclusion in this study, summarizing the key findings. The literature supports a common OCT definition of lipid as low-signal regions with diffuse borders, validated against histology and other imaging modalities with acceptable intra- and inter-rater reliability. There is evidence that OCT-identified lipid at the site of stent implantation increases the risk of edge dissection, incomplete stent apposition, in-stent tissue protrusion, decreased coronary flow after stenting, side branch occlusion, and post-procedural cardiac biomarker increases. In mostly retrospective studies, lipid indices measured at non-stented sites are associated with plaque progression and the development of recurrent ischemic events.

CONCLUSIONS

There is extensive literature supporting the ability of OCT to identify lipid and demonstrating a substantial impact of lipid on percutaneous coronary intervention outcomes. Future work to prospectively evaluate the effect of the characteristics of lipid-rich plaques on long-term clinical outcomes is needed.

Comparison of 6-month vascular healing response after bioresorbable polymer versus durable polymer drug-eluting stent implantation in patients with acute coronary syndromes: A randomized serial optical coherence tomography study

Objectives

This study was conducted to use optical coherence tomography (OCT) to compare vascular healing between bioresorbable polymer (BP) and durable polymer (DP) everolimus‐eluting stents (EES) in patients with acute coronary syndromes (ACS).

Background

Whether BP‐EES induce better vascular healing compared to contemporary DP‐EES remains controversial, especially for ACS.

Methods

In this prospective, randomized, non‐inferiority trial, we used OCT to compare 6‐month vascular healing in patients with ACS randomized to BP versus DP‐EES: percent strut coverage (primary endpoint, non‐inferiority margin of 2.0%) and neointimal thickness and percent neointimal hyperplasia (NIH) volume. As an exploratory analysis, morphological factors related to the endpoints and the effect of underlying lipidic plaque on stent healing were evaluated.

Results

A total of 104 patients with ACS were randomly assigned to BP‐EES (n = 52) versus DP‐EES (n = 52). Of these, 86 patients (40 BP‐EES and 46 DP‐EES) were included in the final OCT analyses. Six‐month percent strut coverage of BP‐EES (83.6 ± 11.4%) was not non‐inferior compared to those of DP‐EES (81.6 ± 13.9%), difference 2.0% (lower 95% confidence interval‐2.6%), p_{non‐inferiority} = 0.07. There were no differences in neointimal thickness 70.0 ± 33.9 μm versus 67.2 ± 33.9 μm, p = 0.71; and percent NIH volume 7.5 ± 4.7% versus 7.3 ± 5.3%, p = 0.85. By multivariable linear regression analysis, stent type was not associated with percent strut coverage or percent NIH volume; however, percent baseline embedded struts or stent expansion was positively associated with percent NIH volume. Greater NIH volume was observed in lipidic compared with non‐lipidic segments (8.7 ± 5.6% vs. 6.1 ± 5.2%, p = 0.005).

Conclusions

Six‐month strut coverage of BP‐EES was not non‐inferior compared to those of DP‐EES in ACS patients. Good stent apposition and expansion were independently associated with better vascular healing.

Supporting evidence from optical coherence tomography for shortening dual antiplatelet therapy after drug-eluting stents implantation

INTRODUCTION

Dual antiplatelet therapy (DAPT) is required for coronary artery disease treated with drug-eluting stents (DES) implantation. Shortening DAPT duration would be beneficial for patients with high bleeding risk.

AREAS COVERED

Early healing patterns, especially stent strut coverage, assessed by optical coherence tomography (OCT) as a surrogate of neointima have been investigated to make decisions on whether short DAPT would be a safe alternative. This review evaluates the OCT evidence (i.e. neointimal coverage of stent struts within 3 months) for shortening DAPT duration after DES implantation.

EXPERT COMMENTARY

Shortening DAPT (i.e. within 3 months) duration after DES implantation might reduce complications including bleeding without increasing stent thrombosis. However, the optimal duration of DAPT after DES implantation is under discussion. Long-term assessment of short DAPT is required for the decision of the new guidelines regarding the recommended duration of DAPT.

Neointimal coverage after second generation drug-eluting stent implantation has a relationship with pre-existing atherosclerotic lesion characteristics

The relationship between preexisting atherosclerotic lesion characteristics and neointimal thickness after second-generation drug-eluting stent (DES) placement is still unknown. Thus, we evaluated that relationship using optical coherence tomography (OCT).A single-center, retrospective, observational study was conducted. Patients with stable angina or asymptomatic myocardial ischemia who received percutaneous coronary intervention for a de novo lesion using a second-generation DES under frequency domain OCT guidance and underwent follow-up coronary angiography (CAG) and OCT between December 2010 and December 2015 were included. The relationship between the neointimal thickness on the stent strut and the plaque characteristics was retrospectively evaluated using OCT immediately after stent implantation and at the time of follow-up CAG.We analyzed 3459 struts from 20 stents in 15 patients. The mean follow-up period was 264 days. In the follow-up study, no angiographic in-stent restenosis was found. Of the 3459 struts, 3315 (95.8%) were covered with neointima. The median neointimal thicknesses of the stent struts on calcified, fibrous, and lipid-rich lesions were 20 μm (interquartile range [IQR], 10-50 μm), 70 μm (40-140 μm; P < .001), and 90 μm (50-170 μm; P < .001), respectively. These differences were observed regardless of the type of second-generation DES used.Most of the stent struts were covered with neointima. The neointimal thickness after the second-generation DES implantation had a close relationship with the preexisting atherosclerotic lesion characteristics. In this study, we found differences in arterial healing processes due to underlying plaque; therefore, evaluating the lesion characteristics by OCT may predict the risk for future restenosis and thrombosis.