Pathologic Etiologies of Late and Very Late Stent Thrombosis following First-Generation Drug-Eluting Stent Placement

The Mechanical and Electrochemical Stability of Trimethysilane Plasma Nanocoatings Deposited onto Cobalt Chromium Cardiovascular Stents

The objective of this study was to evaluate the coating integrity performance and corrosion protection property of trimethylsilane (TMS) plasma nanocoatings that were directly deposited onto cobalt chromium (CoCr) L605 cardiovascular stents. Hydrophilic surfaces were achieved for the TMS plasma nanocoatings that were deposited onto the coronary stents through NH3/O2 (2:1 molar ratio) plasma post-treatment. With a coating thickness of approximately 20-25 nm, the TMS plasma nanocoatings were highly durable and able to resist delamination and cracking from crimping and expansion by a Model CX with a J-Crimp Station. The stent surface that was evaluated by Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) showed no indications of pitting, corrosion, or adsorption products on either the luminal or abluminal surfaces of the stents, in contrast to the uncoated stent surface. The TMS plasma nanocoatings significantly enhanced the stent's corrosion resistance in immersion experiments that followed the ASTM F2129-15 corrosion protocol, evident in the increase of the open circuit potential (OCP) from 0.01 V for the uncoated L605 stent to 0.18 V for the plasma-nanocoated L605 stent, reducing potential cytotoxic metal ion release. Cyclic polarization (CP) curves show that the corrosion rate (density level) observed in plasma-nanocoated L605 stents was approximately half an order of magnitude lower than that of the uncoated stents, indicating improved corrosion protection of the stents. CP curves of the TMS plasma-nanocoated stents with different coating thicknesses show that, in the range of 20-65 nm, the coating thickness does not result in any difference in the corrosion resistance of the stents.

Pro-Healing Nanomatrix-Coated Stent Analysis in an In Vitro Vascular Double-Layer System and in a Rabbit Model

Cardiovascular stent technologies have significantly improved over time. However, their optimal performance remains limited by restenosis, thrombosis, inflammation, and delayed re-endothelialization. Current stent designs primarily target inhibition of neointimal proliferation but do not promote functional arterial healing (pro-healing) in order to restore normal vascular reactivity. The endothelial lining that does develop with current stents appears to have loose intracellular junctions. We have developed a pro-healing nanomatrix coating for stents that enhances healing while limiting neointimal proliferation. This builds on our prior work evaluating the effects of the pro-healing nanomatrix coating on cultures of vascular endothelial cells (ECs), smooth muscle cells (SMCs), monocytes, and platelets. However, when a stent is deployed in an artery, multiple vascular cell types interact, and their interactions affect stent performance. Thus, in our current study, an in vitro vascular double-layer (VDL) system was used to observe stent effects on communication between different vascular cell types. Additionally, we assessed the pro-healing ability and vascular cell interactions after stent deployment in the VDL system and in a rabbit model, evaluating the nanomatrix-coated stent compared to a commercial bare metal stent (BMS) and a drug eluting stent (DES). In vitro results indicated that, in a layered vascular structure, the pro-healing nanomatrix-coated stent could (1) improve endothelialization and endothelial functions, (2) regulate SMC phenotype to reduce SMC proliferation and migration, (3) suppress inflammation through a multifactorial manner, and (4) reduce foam cell formation, extracellular matrix remodeling, and calcification. Consistent with this, in vivo results demonstrated that, compared with commercial BMS and DES, this pro-healing nanomatrix-coated stent enhanced re-endothelialization with negligible restenosis, inflammation, or thrombosis. Thus, these findings indicate the unique pro-healing features of this nanomatrix stent coating with superior efficacy over commercial BMS and DES.

Drug-Eluting, Bioresorbable Cardiovascular Stents─Challenges and Perspectives

Globally, the leading causes of natural death are attributed to coronary heart disease and type 1 and type 2 diabetes. High blood pressure levels, high cholesterol levels, smoking, and poor eating habits lead to the agglomeration of plaque in the arteries, reducing the blood flow. The implantation of devices used to unclog vessels, known as stents, sometimes results in a lack of irrigation due to the excessive proliferation of endothelial tissue within the blood vessels and is known as restenosis. The use of drug-eluting stents (DESs) to deliver antiproliferative drugs has led to the development of different encapsulation techniques. However, due to the potency of the drugs used in the initial stent designs, a chronic inflammatory reaction of the arterial wall known as thrombosis can cause a myocardial infarction (MI). One of the most promising drugs to reduce this risk is everolimus, which can be encapsulated in lipid systems for controlled release directly into the artery. This review aims to discuss the current status of stent design, fabrication, and functionalization. Variables such as the mechanical properties, metals and their alloys, drug encapsulation and controlled elution, and stent degradation are also addressed. Additionally, this review covers the use of polymeric surface coatings on stents and the recent advances in layer-by-layer coating and drug delivery. The advances in nanoencapsulation techniques such as liposomes and micro- and nanoemulsions and their functionalization in bioresorbable, drug-eluting stents are also highlighted.

Optimize PLA/EVA Polymers Blend Compositional Coating for Next Generation Biodegradable Drug-Eluting Stents

In this research work, polymer blends of poly-lactic acid (PLA)/ethylene vinyl acetate (EVA) were prepared as the drug carrier materials for a bi-layer drug-loaded coating film for coronary stents. Different optimum compositions of blends were prepared by using an intense mixer. Then, the blends were hot-pressed and later cold-pressed to prepare for films of different thickness. The changes in weight, surface analysis and biodegradability with increasing time were studied using Scanning electron microscopy (SEM), weight loss and biodegradability tests. The mechanical and thermal properties of drug-loaded films were studied through universal testing machine (UTM) and thermo-gravimetric analysis (TGA). The effects of PLA, EVA and drug contents on in-vitro drug contents were investigated through the Ultraviolet-Visible Spectroscopy (UV-VIS) chemical analysis technique. The results obtained clearly showed that the addition of PLA promoted the unleashing of the drug whereas the addition of EVA nearly did not have the same affect. The mechanical properties of these various films can be tuned by adjusting the contents of blend parts. The factors affecting the unleashing of the drug became a serious matter of concern in evaluating the performance of bio-resorbable drug eluting stents. As a result, today’s chemical blends may be useful drug carrier materials for drug-loaded tube coatings capable delivering purgative drug in an incredibly tunable and regulated manner.

Relationship between atherogenic index of plasma and stent thrombosis in patients with acute coronary syndrome

OBJECTIVE

Stent thrombosis (ST) is an uncommon but serious complication in patients undergoing percutaneous coronary intervention (PCI). This study aimed to investigate the effect of atherogenic index of plasma (AIP) on ST.

METHODS

Among the 10,258 patients who underwent coronary angiography between January 2018 and December 2020, 239 patients who underwent PCI with the diagnosis of acute coronary syndrome (ACS) due to ST were included as the study group (ST group) and 459 patients who underwent percutaneous intervention for ACS and did not have any in-stent lesion as the control group (non-ST group). ST classification was done according to the Academic Research Consortium definition.

RESULTS

The mean age of the patients was 63.3±10.6 years (483 male, 69.2%). The groups were similar in terms of characteristic properties, comorbidities, and the drugs being used (p>0.05 for all). Drug eluting stents were used in 86.5% of the patients. In the ST group, the median time from stent implantation to thrombosis was 285 days. Mean AIP and the ratio of triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) were statistically significantly higher in the ST group than in the controls (p<0.001 and p=0.018, respectively), and a positive correlation was observed between time from stent implantation to thrombosis and AIP and TG/HDL-C (rS=0.229, p=0.010 and rS=0.222, p=0.010, respectively). Multivariate logistic regression analysis revealed that stent length, prior ST elevation myocardial infarction, TG/HDL-C, and AIP were independent predictors of ST.

CONCLUSION

AIP is an easy calculable biomarker, and the performance of AIP to predict ST is better than TG/HDL-C.

Early vascular healing after implantation of the polymer-free biolimus-eluting stent or the ultrathin strut biodegradable polymer sirolimus-eluting stent in patients with ST-segment elevation myocardial infarction

OBJECTIVE

To evaluate the difference in early vascular healing between the ultrathin-strut biodegradable-polymer sirolimus-eluting Orsiro stent (O-SES) and the polymer-free biolimus-A9-eluting BioFreedom stent (BF-BES), assessed with optical coherence tomography (OCT) after primary percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarctions (STEMIs).

METHODS

Eighty patients with STEMI who underwent primary PCI were randomly allocated 1:1 to treatment with BF-BES or O-SES. OCT was acquired after PCI and at 1-month follow-up. The primary endpoint was 1-month OCT-assessed vascular healing index based on the presence of uncovered and malapposed stent struts and intraluminal filling defects where low vascular healing index indicated favorable vascular healing.

RESULTS

At 1-month, the vascular healing index was similar in O-SES 11.5 [interquartile range (IQR) 9.5-17.5], compared to BF-BES 11.5 (IQR 7.1-12.5; P = 0.14). Percentage of uncovered struts [O-SES 31.5% (IQR 20.7-41.9), P = 0.43] vs. BF-BES 27.8% (IQR 19.4-41.9; P = 0.44), and median volume of neointimal hyperplasia [O-SES 4.9 mm3 (IQR 1.4-13.1) vs. BF-BES 7.1 mm3 (IQR 2.8-17.0), P = 0.18] did not differ significantly between the two stent groups. Complete coverage was not observed in any of the stents. The percentages of stents with malapposition did not differ significantly (O-SES 87.1% vs. BF-BES 71.4%, P = 0.14) whereas percentage of malapposed struts [O-SES 3.5% (IQR 0.8-5.5) vs. BF-BES 0.8% (IQR 0.0-1.8), P = 0.003] was lower in the BF-BES group.

CONCLUSION

In patients with STEMI, the drug-coated BF-BES and the thin strut O-SES had similar vascular healing index at 1-month. However, the thin O-SES struts were more often malapposed.

Impact of stent malapposition on intracoronary flow dynamics: An optical coherence tomography-based patient-specific study

Percutaneous coronary intervention with stent implantation has emerged as a popular approach to treat coronary artery stenosis. Stent malapposition (SM), also referred as incomplete stent apposition, could reduce stent tissue coverage and hence increase the risk of late stent thrombosis. The objective of this study was to investigate the impact of SM on intracoronary flow dynamics by combining optical coherence tomography (OCT) image-based model reconstruction and computational analysis. Firstly, a stenosed coronary artery model was reconstructed from OCT and angiography imaging data of a patient. Two structural analyses were carried out to simulate two types of coronary artery stent implantations: a fully-apposed (FA) case and a SM case. Then, based on the two deformed coronary geometries, two computational fluid dynamics (CFD) analyses were performed to evaluate the differences of hemodynamic metrics between the FA and the SM cases, including wall shear stress (WSS), time-averaged WSS (TWSS), oscillatory shear index (OSI), WSS gradient (WSSG), time-averaged WSSG (TWSSG), and relative residence time (RRT). The results indicated that maximum flow velocity was higher in the SM case than that of the FA case, due to the incomplete expansion of the stent and artery. Moreover, the SM case had a lower percentage of areas of adverse WSS (< 0.5 Pa) and RRT (> 10/Pa) but a higher percentage of areas of adverse OSI (> 0.1) and WSSG (> 5000 Pa/m). Specifically, the differences of OSI, WSSG, and RRT between the two cases were relatively small. It was suggested that SM might not be responsible for negative hemodynamic metrics which would further result in stent thrombosis on the basis of the present specific model.

Early Vascular Healing Following Bioresorbable-Polymer Sirolimus-Eluting Stent Placement Compared to That with Durable-Polymer Everolimus-Eluting Stent

A recent thinner strut drug-eluting stent might facilitate early strut coverage after its placement. We aimed to investigate early vascular healing responses after the placement of an ultrathin-strut bioresorbable-polymer sirolimus-eluting stent (BP-SES) compared to those with a durable-polymer everolimus-eluting stent (DP-EES) using optical coherence tomography (OCT) imaging.This study included 40 patients with chronic coronary syndrome (CCS) who underwent OCT-guided percutaneous coronary intervention (PCI). Twenty patients each received either BP-SES or DP-EES implantation. OCT was performed immediately after stent placement (baseline) and at 1-month follow-up.At one month, the percentage of uncovered struts reduced significantly in both the BP-SES (80.9 ± 10.3% to 2.9 ± 1.7%; P < 0.001) and DP-EES (81.9 ± 13.0% to 5.7 ± 1.8%; P < 0.001) groups, and the percentage was lower in the BP-SES group than in the DP-EES group (P < 0.001). In the BP-SES group, the percentage of malapposed struts also decreased significantly at 1 month (4.9 ± 3.7% to 2.6 ± 3.0%; P = 0.025), which was comparable to that of the DP-EES group (2.5 ± 2.2%; P = 0.860). The optimal cut-off value of the distance between the strut and vessel surface immediately after the placement to predict resolved malapposed struts was ≤ 160 μm for BP-SES and ≤ 190 μm for DP-EES.Compared to DP-EES, ultrathin-strut BP-SES demonstrated favorable vascular responses at one month, with a lower rate of uncovered struts and a comparable rate of malapposed struts.

Cardiovascular Stents: A Review of Past, Current, and Emerging Devices

One of the leading causes of morbidity and mortality worldwide is coronary artery disease, a condition characterized by the narrowing of the artery due to plaque deposits. The standard of care for treating this disease is the introduction of a stent at the lesion site. This life-saving tubular device ensures vessel support, keeping the blood-flow path open so that the cardiac muscle receives its vital nutrients and oxygen supply. Several generations of stents have been iteratively developed towards improving patient outcomes and diminishing adverse side effects following the implanting procedure. Moving from bare-metal stents to drug-eluting stents, and recently reaching bioresorbable stents, this research field is under continuous development. To keep up with how stent technology has advanced in the past few decades, this paper reviews the evolution of these devices, focusing on how they can be further optimized towards creating an ideal vascular scaffold.

Impact of Malapposed and Overlapping Stents on Hemodynamics: A 2D Parametric Computational Fluid Dynamics Study

Despite significant progress, malapposed or overlapped stents are a complication that affects daily percutaneous coronary intervention (PCI) procedures. These malapposed stents affect blood flow and create a micro re-circulatory environment. These disturbances are often associated with a change in Wall Shear Stress (WSS), Time-averaged WSS (TAWSS), relative residence time (RRT) and oscillatory character of WSS and disrupt the delicate balance of vascular biology, providing a possible source of thrombosis and restenosis. In this study, 2D axisymmetric parametric computational fluid dynamics (CFD) simulations were performed to systematically analyze the hemodynamic effects of malapposition and stent overlap for two types of stents (drug-eluting stent and a bioresorbable stent). The results of the modeling are mainly analyzed using streamlines, TAWSS, oscillatory shear index (OSI) and RRT. The risks of restenosis and thrombus are evaluated according to commonly accepted thresholds for TAWSS and OSI. The small malapposition distances (MD) cause both low TAWSS and high OSI, which are potential adverse outcomes. The region of low OSI decrease with MD. Overlap configurations produce areas with low WSS and high OSI. The affected lengths are relatively insensitive to the overlap distance. The effects of strut size are even more sensitive and adverse for overlap configurations compared to a well-applied stent.

In vivo evaluation of a pro-healing polydopamine coated stent through an in-stent restenosis rat model

Drug-eluting stents have demonstrated efficiency in in-stent restenosis (ISR) but induced a risk of late acute thrombosis by delaying strut re-endothelialization. Polydopamine (PDA), a biocompatible polymer inspired from adhesive proteins of mussels, has been reported to promote endothelial cell (EC) proliferation while limiting SMC proliferation in vitro, thus suggesting the pro-healing potential. This study aimed at evaluating in vivo the impact of the pro-healing PDA-coated stent on ISR and on the quality of the strut re-endothelialization in a rat model. PDA-coated stents demonstrated a significant reduction in ISR in vivo compared to bare metal stents (ratio neointima/media = 0.48 (±0.26) versus 0.83 (±0.42), p < 0.001). Western blot analyses identified a trend towards an increased activation of p38 MAPK phosphorylation and its anti-proliferative effects on vascular SMC that could explain the results observed in morphological analyses. This bioinspired and biocompatible polydopamine layer could intrinsically limit ISR. In addition, according to its latent reactivity, PDA offers the possibility to immobilize some relevant drugs on the PDA-functionalized stent to provide potential synergistic effects.

Optical Coherence Tomography: Current Applications for the Assessment of Coronary Artery Disease and Guidance of Percutaneous Coronary Interventions

INTRODUCTION

Coronary angiography (CAG) is the standard modality for assessment of coronary stenoses and intraprocedural guidance of percutaneous coronary interventions (PCI). However, the limitations of CAG are well recognized. Intracoronary imaging (ICI) can potentially overcome these limitations. Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) are the main ICI techniques utilized in clinical practice.

AIM

This narrative literature review addresses the current clinical applications of OCT in relation to IVUS and CAG in patients with coronary artery disease (CAD). Items reviewed are: technical implications of OCT and IVUS, lesion characterization and decision-making, stent optimization criteria, post-stenting results, safety in terms of procedural complications, clinical outcomes, and indications.

MAIN FINDINGS

OCT is able to reveal more detail than IVUS due to its higher resolution. However, this higher resolution comes at the cost of a lower penetration depth. Pre-stenting OCT results in procedural change in more than 50% of the cases in terms of stent length and diameter. Post-stenting OCT resulting in stent optimization is reported in at least 27% of the cases. Malapposition and under-expansion are treated with post-dilatations, while edge dissections are treated with additional stent placement. Stent expansion, stent apposition, distal stent edge dissections, and reference lumen areas seem to be the most important stent optimization criteria for both decision-making and for reducing the risk of adverse events during follow-up. Both OCT and IVUS are superior in terms of post-stenting results compared with CAG alone. However, there is no consensus about whether OCT guidance results in better stent expansion than IVUS guidance. OCT, IVUS, and CAG are safe procedures with few reported procedural complications. In general, OCT guidance seems to contribute to favorable clinical outcomes compared with CAG guidance only. However, OCT guidance results in similar clinical outcomes as with IVUS guidance. OCT could be considered for lumen assessment and stent-related morphology in more complex cases in which CAG interpretation remains uncertain. Since OCT and IVUS have distinct characteristics, these techniques are complementary and should be considered carefully for each patient case based on the benefits and limitations of both techniques.

Red Blood Cells and Hemoglobin in Human Atherosclerosis and Related Arterial Diseases

As the main particulate component of the circulating blood, RBCs play major roles in physiological hemodynamics and impact all arterial wall pathologies. RBCs are the main determinant of blood viscosity, defining the frictional forces exerted by the blood on the arterial wall. This function is used in phylogeny and ontogeny of the cardiovascular (CV) system, allowing the acquisition of vasomotricity adapted to local metabolic demands, and systemic arterial pressure after birth. In pathology, RBCs collide with the arterial wall, inducing both local retention of their membranous lipids and local hemolysis, releasing heme-Fe⁺⁺ with a high toxicity for arterial cells: endothelial and smooth muscle cells (SMCs) cardiomyocytes, neurons, etc. Specifically, overloading of cells by Fe⁺⁺ promotes cell death. This local hemolysis is an event associated with early and advanced stages of human atherosclerosis. Similarly, the permanent renewal of mural RBC clotting is the major support of oxidation in abdominal aortic aneurysm. In parallel, calcifications promote intramural hemorrhages, and hemorrhages promote an osteoblastic phenotypic shift of arterial wall cells. Different plasma or tissue systems are able, at least in part, to limit this injury by acting at the different levels of this system.

Impact of strut dimensions and vessel caliber on thrombosis risk of bioresorbable scaffolds using hemodynamic metrics

Bioresorbable scaffolds (BRS) promise to be the treatment of choice for stenosed coronary vessels. But higher thrombosis risk found in current clinical studies limits the expectations. Three hemodynamic metrics are introduced to evaluate the thrombosis risk of coronary stents/scaffolds using transient computational fluid dynamics (CFD). The principal phenomena are platelet activation and effective diffusion (platelet shear number, PSN), convective platelet transport (platelet convection number, PCN) and platelet aggregation (platelet aggregation number, PAN) were taken into consideration. In the present study, two different stent designs (thick-strut vs. thin-strut design) positioned in small- and medium-sized vessels (reference vessel diameter, RVD=2.25 mm vs. 2.70 mm) were analyzed. In both vessel models, the thick-strut design induced higher PSN, PCN and PAN values than the thin-strut design (thick-strut vs. thin-strut: PSN=2.92/2.19 and 0.54/0.30; PCN=3.14/1.15 and 2.08/0.43; PAN: 14.76/8.19 and 20.03/10.18 for RVD=2.25 mm and 2.70 mm). PSN and PCN are increased by the reduction of the vessel size (PSN: RVD=2.25 mm vs. 2.70 mm=5.41 and 7.30; PCN: RVD=2.25 mm vs. 2.70 mm=1.51 and 2.67 for thick-strut and thin-strut designs). The results suggest that bulky stents implanted in small caliber vessels may substantially increase the thrombosis risk. Moreover, sensitivity analyses imply that PSN is mostly influenced by vessel size (lesion-related factor), whereas PCN and PAN sensitively respond to strut-thickness (device-related factor).

Clinical, Angiographic, and Procedural Correlates of Very Late Absorb Scaffold Thrombosis: Multistudy Registry Results

OBJECTIVES

The aim of this study was to identify independent correlates of very late scaffold thrombosis (VLST) from an analysis of consecutively treated patients from 15 multicenter studies.

BACKGROUND

Recent analyses suggest an increased risk for VLST with the Absorb Bioresorbable Vascular Scaffold compared with drug-eluting stents, but insights as to correlates of risk are limited.

METHODS

A total of 55 patients were identified with scaffold thrombosis. They were matched 2:1 with control subjects selected randomly from patients without thrombosis from the same study. Quantitative coronary angiography was available for 96.4% of patients. Multiple logistic and Cox regression analysis were used to identify significant independent outcome correlates from 6 pre-specified characteristics.

RESULTS

Patients had scaffold thrombosis at a median of 20 months (interquartile range: 17 to 27 months). Control subjects were followed for 36 months (interquartile range: 24 to 38 months). For the combined groups, reference vessel diameter (RVD) was 2.84 ± 0.50 mm, scaffold length was 26 ± 16 mm, and post-dilatation was performed in 56%. Univariate correlates of thrombosis were smaller nominal scaffold/RVD ratio (linear p = 0.001; ratio <1.18:1; odds ratio: 7.5; p = 0.002) and larger RVD (linear p = 0.001; >2.72 mm; odds ratio: 3.4; p = 0.001). Post-dilatation at ≥16 atm, post-dilatation balloon/scaffold ratio, final percentage stenosis, and dual antiplatelet therapy were not correlated with VLST. Only scaffold/RVD ratio remained a significant independent correlate of VLST (p = 0.001), as smaller ratio was correlated with RVD (p < 0.001). Post hoc analysis of 8 other potential covariates revealed no other correlates of outcome.

CONCLUSIONS

In the present analysis, the largest to date of its type, relative scaffold undersizing was the strongest determinant of VLST. Given current understanding of "scaffold dismantling," this finding likely has ramifications for all bioresorbable scaffolds.

Neoatherosclerosis after drug-eluting stent implantation: a novel clinical and therapeutic challenge

The recognition that obstructive disease of the epicardial coronary arteries, causing ischaemic heart disease, can be treated with a percutaneous coronary intervention (PCI) has been a major discovery in cardiology in the last 40 years contributing, in particular, to the reduction of mortality associated to acute myocardial infarction (AMI). However, even in the era of drug-eluting stent (DES) implantation, a sizable proportion of patients who undergo PCI may develop late or very late post-implantation complications, that occur in the form of restenosis, neoatherosclerosis, and/or in-stent thrombosis. Such complications are clinically relevant since they can cause AMI and negatively impact on the outcome. The underlying pathophysiological mechanisms are complex but related to inhibition of neointimal proliferation by DES that, on the hand, reduces the rate of in-stent restenosis, but, on the other hand, causes dysfunctional vessel healing, persistent inflammation, platelet activation, and adverse immunological responses. Multiple approaches have been developed or are under evaluation to target DES-related complications including pharmacotherapy, procedure-related imaging methods, novel stent designs, and drug-delivery methods. The aim of this review is to provide an update on the latest preclinical, translational, and clinical pharmacotherapeutic developments in this setting that target novel cellular mechanisms and pathways that might contribute to neoatherosclerosis. Due to the importance of secondary prevention in the reduction of DES-associated complications, this review also provides a short overview of pharmacological agents that are established or currently being investigated in this regard.

In vivo Molecular Imaging of Glutamate Carboxypeptidase II Expression in Re-endothelialisation after Percutaneous Balloon Denudation in a Rat Model

The short- and long-term success of intravascular stents depends on a proper re-endothelialisation after the intervention-induced endothelial denudation. The aim of this study was to evaluate the potential of in vivo molecular imaging of glutamate carboxypeptidase II (GCPII; identical with prostate-specific membrane antigen PSMA) expression as a marker of re-endothelialisation. Fifteen Sprague Dawley rats underwent unilateral balloon angioplasty of the common carotid artery (CCA). Positron emission tomography (PET) using the GCPII-targeting tracer [¹⁸F]DCFPyL was performed after 5-21 days (scan 60-120 min post injection). In two animals, the GCPII inhibitor PMPA (23 mg/kg BW) was added to the tracer solution. After PET, both CCAs were removed, dissected, and immunostained with the GCPII specific antibody YPSMA-1. Difference of GCPII expression between both CCAs was established by PCR analysis. [¹⁸F]DCFPyL uptake was significantly higher in the ipsilateral compared to the contralateral CCA with an ipsi-/contralateral ratio of 1.67 ± 0.39. PMPA blocked tracer binding. The selective expression of GCPII in endothelial cells of the treated CCA was confirmed by immunohistological staining. PCR analysis verified the site-specific GCPII expression. By using a molecular imaging marker of GCPII expression, we provide the first non-invasive in vivo delineation of re-endothelialisation after angioplasty.

Drug-Coated Balloon Versus Drug-Eluting Stent in Primary Percutaneous Coronary Intervention: A Feasibility Study

BACKGROUND

Drug-eluting stents (DES) represent a significant evolution in the treatment of patients with acute myocardial infarction with ST elevation. However, stent-related adverse events have led to an introduction of drug-coated balloons (DCB) applied particularly to bifurcation lesions, in-stent restenosis and small vessel disease. The aim of this study was to determine whether a DCB-only strategy has a similar safety profile and equal angiographic and clinical outcomes to DES implantation in primary percutaneous coronary intervention (pPCI).

MATERIALS AND METHODS

Seventy-five patients with acute myocardial infarction with ST elevation were randomized into DES and DCB groups of 37 and 38 patients, respectively. The study end-points were major adverse cardiac events and late lumen loss during the 6 months following the pPCI.

RESULTS

Reinfarction occurred in 5.4% of patients in the DES and 5.3% of patients in the DCB group after 1 month (risk ratio = 1.03, 95% CI [0.15-6.91], P = 0.98). After 6 months, major adverse cardiac events were reported in 5.4% of patients in the DES group and none in the DCB group (risk ratio = 5.13, 95% CI [0.25-103.42], P = 0.29). Late lumen loss in the DES group was 0.10 ± 0.19mm and -0.09 ± 0.09mm in the DCB group (P < 0.05).

CONCLUSIONS

A DCB-only strategy is safe and feasible in the pPCI setting and showed good clinical and angiographic outcomes in a 6-month follow-up period.

Optical coherence tomography evaluation of intermediate-term healing of different stent types: systemic review and meta-analysis

AIMS

The intermediate-term incidence of strut malapposition (SM) and uncovered struts (US), and the degree of neointimal thickness (NIT) according to stent type have not been characterized.

METHODS AND RESULTS

All studies of >50 patients in which optical coherence tomography was performed between 6 and 12 months after stent implantation were included. The incidences of SM and US were the co-primary end points, while NIT was the secondary end point. A total of 458 citations were initially appraised at the abstract level, and 11 full-text studies (280 652 analysed struts, 921 patients) were assessed. The 6-12 months incidences of SM and US were 5.0 and 7.8%, respectively, and the mean NIT was 206 μm. Biolimus-eluting stents (BES) and bioresorbable vascular scaffolds (BVS) had the highest SM rates (2.7 and 3.8%, respectively), while everolimus-eluting stents (EES) and fast-release zotarolimus-eluting stents (ZES) had the lowest SM rates (0.9 and 0.1%, respectively). BES and sirolimus-eluting stents (SES) had the highest US rates (7.7 and 8.8%, respectively), while bare metal stents (BMS) and ZES had the lowest US rates (0.3 and 0.3%, respectively). BMS had the greatest NIT (340 μm), while SES, EES, and BES had the least NIT.

CONCLUSION

Second-generation drug-eluting stents (DES) have better intermediate-term strut apposition and coverage than first-generation DES, BVS, and BMS. EES demonstrate the overall best combination of healing with suppression of neointimal hyperplasia at 6-12 months. Further studies with clinical correlation are warranted to determine the implications of these findings.

[Drug-coated balloons in the treatment of peripheral artery disease (PAD). History and current level of evidence]

BACKGROUND

Despite initially encouraging technical success after femoropopliteal PTA, restenosis remains the major challenge in patients with peripheral artery disease (PAD). The main cause of restenosis is neointimal hyperplasia which can be suppressed by antiproliferative drugs. Drug-coated balloons (DCB) or drug-eluting stents (DES) are used for the inhibition of restenosis.

OBJECTIVES

The present article gives an overview of DCB development, actual DCB systems for femoro- and infrapopliteal use, displays the outcomes of randomized clinical trials and the discusses the evidence for the DCB treatment in PAD.

METHODS

A systematic literature search was performed in i) medical journals (i. e. MEDLINE), ii) in international registers for clinical studies (i. e. www.clinicaltrials.gov ) and in iii) scientific session abstracts.

RESULTS

The clinical evidence of the PTX-DCB of the first and following generation has been shown in several controlled randomized trials.

CONCLUSIONS

Major advantages of the DCBs lie in leaving no stent scaffold behind, the immediate release of high drug concentrations with a single dosage, their efficacy in areas, where stents have been contra-indicated until now and its use for secondary interventions. As their effect seems to be limited in severely calcified lesions, prior plaque preconditioning or removal could be advantageous. First positive results data supporting this hypothesis do exist.

Peristrut microhemorrhages: a possible cause of in-stent neoatherosclerosis?

BACKGROUND

In-stent neoatherosclerosis is characterized by the delayed appearance of markers of atheroma in the subintima, but the pathophysiology underlying this new disease entity remains unclear.

METHODS AND RESULTS

We collected 20 human coronary artery stents by removal from explanted hearts. The mean duration of stent implantation was 34 months. In all samples, neoatherosclerosis was detected, particularly in peristrut areas. It consisted of foam cells and cholesterol clefts, with or without calcification, associated with neovascularization. Iron and glycophorin-A were present in peristrut areas, as well as autofluorescent ceroids. Moreover, in response to neoatherosclerosis, tertiary lymphoid organs (tissue lymphoid clusters) often developed in the adventitia. Some of these features could be reproduced in an experimental carotid stenting model in rabbits fed a high-cholesterol diet. Foam cells were present in all samples, and peristrut red blood cells (RBCs) were also detected, as shown by iron deposits and Bandeiraea simplicifiola isolectin-B4 staining of RBC membranes. Finally, in silico models were used to evaluate the compliance mismatch between the rigid struts and the distensible arterial wall using finite element analysis. They show that stenting approximately doubles the local von Mises stress in the intimal layer.

CONCLUSIONS

We show here that stent implantation both in human and in rabbit arteries is characterized by local peristrut microhemorrhages and finally by both cholesterol accumulation and oxidation, triggering together in-stent neoatherosclerosis. Our data indicate that these processes are likely initiated by an increased mechanical stress due to the compliance mismatch between the rigid stent and the soft wall.

Optical Coherence Tomography Findings in Bioresorbable Vascular Scaffolds Thrombosis

BACKGROUND

Everolimus-eluting bioresorbable vascular scaffolds have been developed to improve late outcomes after coronary interventions. However, recent registries raised concerns regarding an increased incidence of scaffold thrombosis (ScT). The mechanism of ScT remains unknown.

METHODS AND RESULTS

The present study investigated angiographic and optical coherence tomography findings in patients experiencing ScT. Fifteen ScT (14 patients, 79% male, age 59±10 years) occurred at a median of 16 days (25%-75% interquartile range: 1-263 days) after implantation. Early ScT (<30 days) occurred in 8 cases (53%). Possible causal factors in these patients included insufficient platelet inhibition in 2 cases and procedural factors (scaffold underexpansion, undersizing, or geographical miss) in 4 cases. No obvious cause could be found in 2 early ScT. In late (>1 month) and very late (>1 year) ScT (respectively, 5 and 2 cases), 5 scaffolds showed intimal neovessels or marked peristrut low-intensity areas. Scaffold fractures were additionally found in 2 patients, and scaffold collapse was found in 1 patient with very late ScT. Extensive strut malapposition was the presumed cause for ScT in 1 case. One scaffold did not show any morphological abnormality. Thrombectomy specimens were analyzed in 3 patients and did not demonstrate increased numbers of inflammatory cells.

CONCLUSIONS

The mechanisms of early ScT seem to be similar to metallic stents (mechanical and inadequate antiplatelet therapy). The predominant finding in late and very late ScT is peristrut low-intensity area.

Optical Coherence Tomography Guided Percutaneous Coronary Intervention With Nobori Stent Implantation in Patients With Non-ST-Segment-Elevation Myocardial Infarction (OCTACS) Trial: Difference in Strut Coverage and Dynamic Malapposition Patterns at 6 Months

BACKGROUND

Incomplete strut coverage has been documented an important histopathologic morphometric predictor for later thrombotic events. This study sought to investigate whether optical coherence tomography (OCT)-guided percutaneous coronary intervention with Nobori biolimus-eluting stent implantation in patients with non-ST-segment-elevation myocardial infarction would provide improved strut coverage at 6 months in comparison with angiographic guidance only.

METHODS AND RESULTS

One hundred patients were randomized 1:1 to either OCT-guided or angio-guided Nobori biolimus-eluting stent implantation. Postprocedure OCT was performed in all patients. In the OCT-guided group, prespecified criteria indicating additional intervention were related to (1) stent underexpansion, (2) strut malapposition, (3) edge dissection(s), and (4) residual stenosis at the distal or proximal reference segment(s). A final OCT was performed in case of reintervention. Six-month OCT follow-up was available in 85 patients. Twenty-three (46%) OCT-guided patients had additional postdilation or stenting. The percentage of acutely malapposed struts was substantially lower in the OCT-guided group (3.4% [interquartile range, 0.3-7.6] versus 7.8% [interquartile range, 2.3-19.4]; P<0.01). At 6-month follow-up, the OCT-guided group had a significantly lower proportion of uncovered struts; 4.3% [interquartile range, 1.2-9.8] versus 9.0% [interquartile range, 5.5-14.5], P<0.01. Furthermore, OCT-guided patients had significantly more completely covered stents: 17.5% versus 2.2%, P=0.02. The percentages of malapposed struts and struts being both uncovered and malapposed at follow-up were comparable between groups.

CONCLUSIONS

OCT-guided optimization of Nobori biolimus-eluting stent implantation improves strut coverage at 6-month follow-up in comparison with angiographic guidance alone.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02272283.

Biodegradable-Polymer Biolimus-Eluting Stents versus Durable-Polymer Everolimus-Eluting Stents at One-Year Follow-Up: A Registry-Based Cohort Study

We compared outcomes of percutaneous coronary intervention patients who received biodegradable-polymer biolimus-eluting stents with those who received durable-polymer everolimus-eluting stents. At Tehran Heart Center, we performed a retrospective analysis of the data from January 2007 through December 2011 on 3,270 consecutive patients with coronary artery disease who underwent percutaneous coronary intervention with the biodegradable-polymer biolimus-eluting stent or the durable-polymer everolimus-eluting stent. We excluded patients with histories of coronary artery bypass grafting or percutaneous coronary intervention, acute ST-segment-elevation myocardial infarction, or the implantation of 2 different stent types. Patients were monitored for 12 months. The primary endpoint was a major adverse cardiac event, defined as a composite of death, nonfatal myocardial infarction, and target-vessel and target-lesion revascularization. Durable-polymer everolimus-eluting stents were implanted in 2,648 (81%) and biodegradable-polymer biolimus-eluting stents in 622 (19%) of the study population. There was no significant difference between the 2 groups (2.7% vs 2.7%; P=0.984) in the incidence of major adverse cardiac events. The cumulative adjusted probability of major adverse cardiac events in the biodegradable-polymer biolimus-eluting stent group did not differ from that of such events in the durable-polymer everolimus-eluting stent group (hazard ratio=0.768; 95% confidence interval, 0.421-1.44; P=0.388). We conclude that in our patients the biodegradable-polymer biolimus-eluting stent was as effective and safe, during the 12-month follow-up period, as was the durable-polymer everolimus-eluting stent.

Very very late stent thrombosis: 9.5 years after DES implantation

Very late stent thrombosis (VLST) has been recognized as a class effect of 1st generation drug eluting stents (DES) implantation. Although rare, VLST has been reported between 1 and 4 years after DES implantation. Very very late stent thrombosis (VVLST) occurring more than 5 years after DES implantation is extremely rare. We report the first case of a VVLST from India occurring 3465 days (9.5 years) after DES implantation with a brief discussion on its pathogenesis and prevention.

Computational simulation of platelet interactions in the initiation of stent thrombosis due to stent malapposition

Coronary stenting is one of the most commonly used approaches to open coronary arteries blocked due to atherosclerosis. Stent malapposition can induce thrombosis but the microscopic process is poorly understood. The objective of this study was to determine the platelet-level process by which different extents of stent malapposition affect the initiation of stent thrombosis. We utilized a discrete element model to computationally simulate the transport, adhesion, and activation of thousands of individual platelets and red blood cells during thrombus initiation in stented coronary arteries. Simulated arteries contained a malapposed stent with a specified gap distance (0, 10, 25, 50, or 200 μm) between the struts and endothelium. Platelet-level details of thrombus formation near the proximal-most strut were measured during the simulations. The relationship between gap distance and amount of thrombus in the artery varied depending on different conditions (e.g., amount of dysfunctional endothelium, shear-induced activation of platelets, and thrombogenicity of the strut). Without considering shear-induced platelet activation, the largest gap distance (200 μm) produced no recirculation and less thrombus than the smallest two gap distances (0 and 10 μm) that created recirculation downstream of the strut. However, with the occurrence of shear-induced platelet activation, the largest gap distance produced more thrombus than the two smallest gap distances, but less thrombus than an intermediate gap distance (25 μm). A large gap distance was not necessarily the most thrombogenic, in contrast to implications of some computational fluid dynamics studies. The severity of stent malapposition affected initial stent thrombosis differently depending on various factors related to fluid recirculation, platelet trajectories, shear stress, and endothelial condition.

Comparison of a novel biodegradable polymer sirolimus-eluting stent with a durable polymer everolimus-eluting stent: results of the randomized BIOFLOW-II trial

BACKGROUND

Biodegradable polymers for release of antiproliferative drugs from drug-eluting stents aim to improve vascular healing. We assessed noninferiority of a novel ultrathin strut drug-eluting stent releasing sirolimus from a biodegradable polymer (Orsiro, O-SES) compared with the durable polymer Xience Prime everolimus-eluting stent (X-EES) in terms of the primary end point in-stent late lumen loss at 9 months.

METHODS AND RESULTS

A total of 452 patients were randomly assigned 2:1 to treatment with O-SES (298 patients, 332 lesions) or X-EES (154 patients, 173 lesions) in a multicenter, noninferiority trial. The primary end point was in-stent late loss at 9 months. O-SES was noninferior to X-EES for the primary end point (0.10±0.32 versus 0.11±0.29 mm; difference=0.00063 mm; 95% confidence interval, -0.06 to 0.07; Pnoninferiority<0.0001). Clinical outcome showed similar rates of target-lesion failure at 1 year (O-SES 6.5% versus X-EES 8.0%; hazard ratio=0.82; 95% confidence interval, 0.40-1.68; log-rank test: P=0.58) without cases of stent thrombosis. A subgroup of patients (n=55) underwent serial optical coherence tomography at 9 months, which demonstrated similar neointimal thickness among lesions allocated to O-SES and X-EES (0.10±0.04 mm versus 0.11±0.04 mm; -0.01 [-0.04, -0.01]; P=0.37). Another subgroup of patients (n=56) underwent serial intravascular ultrasound at baseline and 9 months indicating a potential difference in neointimal area at follow-up (O-SES, 0.16±0.33 mm(2) versus X-EES, 0.43±0.56 mm(2); P=0.04).

CONCLUSIONS

Compared with durable polymer X-EES, novel biodegradable polymer-based O-SES was found noninferior for the primary end point in-stent late lumen loss at 9 months. Clinical event rates were comparable without cases of stent thrombosis throughout 1 year of follow-up.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT01356888.

ADAMTS-7 Inhibits Re-endothelialization of Injured Arteries and Promotes Vascular Remodeling Through Cleavage of Thrombospondin-1

Background—

ADAMTS-7, a member of the disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) family, was recently identified to be significantly associated genomewide with coronary artery disease. However, the mechanisms that link ADAMTS-7 and coronary artery disease risk remain elusive. We have previously demonstrated that ADAMTS-7 promotes vascular smooth muscle cell migration and postinjury neointima formation via degradation of a matrix protein cartilage oligomeric matrix protein. Because delayed endothelium repair renders neointima and atherosclerosis plaque formation after vessel injury, we examined whether ADAMTS-7 also inhibits re-endothelialization.

Methods and Results—

Wire injury of the carotid artery and Evans blue staining were performed in Adamts7 –/– and wild-type mice. Adamts-7 deficiency greatly promoted re-endothelialization at 3, 5, and 7 days after injury. Consequently, Adamts-7 deficiency substantially ameliorated neointima formation in mice at days 14 and 28 after injury in comparison with the wild type. In vitro studies further indicated that ADAMTS-7 inhibited both endothelial cell proliferation and migration. Surprisingly, cartilage oligomeric matrix protein deficiency did not affect endothelial cell proliferation/migration and re-endothelialization in mice. In a further examination of other potential vascular substrates of ADAMTS-7, a label-free liquid chromatography-tandem mass spectrometry secretome analysis revealed thrombospondin-1 as a potential ADAMTS-7 target. The subsequent studies showed that ADAMTS-7 was directly associated with thrombospondin-1 by its C terminus and degraded thrombospondin-1 in vivo and in vitro. The inhibitory effect of ADAMTS-7 on postinjury endothelium recovery was circumvented in Tsp1 –/– mice.

Conclusions—

Our study revealed a novel mechanism by which ADAMTS-7 affects neointima formation. Thus, ADAMTS-7 is a promising treatment target for postinjury vascular intima hyperplasia.

Simulation of the microscopic process during initiation of stent thrombosis

OBJECTIVE

Coronary stenting is one of the most commonly used approaches to open coronary arteries blocked due to atherosclerosis. However, stent struts can induce stent thrombosis due to altered hemodynamics and endothelial dysfunction, and the microscopic process is poorly understood. The objective of this study was to determine the microscale processes during the initiation of stent thrombosis.

METHODS

We utilized a discrete element computational model to simulate the transport, collision, adhesion, and activation of thousands of individual platelets and red blood cells in thrombus formation around struts and dysfunctional endothelium.

RESULTS

As strut height increased, the area of endothelium activated by low shear stress increased, which increased the number of platelets in mural thrombi. These thrombi were generally outside regions of recirculation for shorter struts. For the tallest strut, wall shear stress was sufficiently low to activate the entire endothelium. With the entire endothelium activated by injury or denudation, the number of platelets in mural thrombi was largest for the shortest strut. The type of platelet activation (by high shear stress or contact with activated endothelium) did not greatly affect results.

CONCLUSIONS

During the initiation of stent thrombosis, platelets do not necessarily enter recirculation regions or deposit on endothelium near struts, as suggested by previous computational fluid dynamics simulations. Rather, platelets are more likely to deposit on activated endothelium outside recirculation regions and deposit directly on struts. Our study elucidated the effects of different mechanical factors on the roles of platelets and endothelium in stent thrombosis.

Analysis by optical coherence tomography of long-term arterial healing after implantation of different types of stents

BACKGROUND

Although drug-eluting stents have significantly reduced the midterm incidence of target lesion revascularization (TLR), in vivo studies on long-term vessel healing of sirolimus-eluting stents (SESs) and paclitaxel-eluting stents (PESs) are limited. The aim of this study was to compare long-term arterial healing with SESs and PESs.

METHODS

We evaluated 27 SESs (23 patients) and 21 PESs (20 patients) by serial optical coherence tomography at 6 months (midphase) and ≥ 3 years (late phase) after stenting and evaluated the change of neointimal thickness (NIT), the percentages of uncovered and malapposed struts, peristrut low-intensity area (region around stent struts with a homogeneously lower intensity appearance than surrounding tissue), thrombus, and atherogenic neointima.

RESULTS

At follow-up, most SESs showed a progressive increase in the average NIT, whereas PESs showed variable changes. Between midphase and late phase, NIT increased significantly in SESs (midphase, 94.1 ± 49.3; late phase, 130.2 ± 78.7; P = 0.001) but decreased significantly in PESs (midphase, 167.4 ± 122.9; late phase, 136.0 ± 77.7; P = 0.04). The percentages of uncovered struts decreased significantly in SESs; conversely, variable changes were observed in PESs. Peristrut low-intensity area and thrombus formation decreased in SESs but remained largely unchanged in PESs. The prevalence of atherogenic neointima was greater in the late phase than in the midphase in both groups but was similar for both stents.

CONCLUSIONS

Long-term vessel healing was different for SESs and PESs. Progressive vessel healing was consistently observed in SESs, whereas a heterogeneous process of delayed vessel healing was noted for PESs.

An agent-based model of the response to angioplasty and bare-metal stent deployment in an atherosclerotic blood vessel

PURPOSE

While animal models are widely used to investigate the development of restenosis in blood vessels following an intervention, computational models offer another means for investigating this phenomenon. A computational model of the response of a treated vessel would allow investigators to assess the effects of altering certain vessel- and stent-related variables. The authors aimed to develop a novel computational model of restenosis development following an angioplasty and bare-metal stent implantation in an atherosclerotic vessel using agent-based modeling techniques. The presented model is intended to demonstrate the body's response to the intervention and to explore how different vessel geometries or stent arrangements may affect restenosis development.

METHODS

The model was created on a two-dimensional grid space. It utilizes the post-procedural vessel lumen diameter and stent information as its input parameters. The simulation starting point of the model is an atherosclerotic vessel after an angioplasty and stent implantation procedure. The model subsequently generates the final lumen diameter, percent change in lumen cross-sectional area, time to lumen diameter stabilization, and local concentrations of inflammatory cytokines upon simulation completion. Simulation results were directly compared with the results from serial imaging studies and cytokine levels studies in atherosclerotic patients from the relevant literature.

RESULTS

The final lumen diameter results were all within one standard deviation of the mean lumen diameters reported in the comparison studies. The overlapping-stent simulations yielded results that matched published trends. The cytokine levels remained within the range of physiological levels throughout the simulations.

CONCLUSION

We developed a novel computational model that successfully simulated the development of restenosis in a blood vessel following an angioplasty and bare-metal stent deployment based on the characteristics of the vessel cross-section and stent. A further development of this model could ultimately be used as a predictive tool to depict patient outcomes and inform treatment options.

Optical coherence tomography characteristics of in-stent restenosis are different between first and second generation drug eluting stents

Aims

Characterization of neointimal tissue is essential to understand the pathophysiology of in-stent restenosis (ISR) after drug eluting stent (DES) implantation. Using optical coherence tomography (OCT), we compared the morphologic characteristics of ISR between first and second generation DES.

Methods and Results

OCT was performed in 66 DES-ISR, defined as > 50% angiographic diameter stenosis within the stented segment. Patients with ISR of first generation sirolimus-eluting stents (SES), paclitaxel eluting stents (PES) and second generation zotarolimus-eluting stents (ZES), everolimus-eluting stents (EES) and biolimus-eluting stents (BES) were enrolled. Quantitative and qualitative ISR tissue analysis was performed at 1-mm intervals along the entire stent, and categorised as homogeneous, heterogeneous and neo-atherosclerosis. The presence of microvessels and peri-strut low intensity area (PSLIA) was determined in all ISR. Neoatherosclerosis was identified by lipid, calcium and thin-cap fibro-atheroma (TCFA) like lesions. We compared the two DES generations at both early (< 1 year) and late (> 1 year) follow-ups.

In second generation DES a heterogeneous pattern was prevalent both before and after 1 year (57.1% and 58.6% respectively). Neo-atherosclerosis was more common in the early period in first generation DES (19.4% vs 11.7%, p < 0.01), but after one year was more prevalent in second generation DES (7.0% vs 19.3%, p < 0.01). Similar prevalence of TCFAs was observed in both groups in all comparisons.

Conclusions

When ISR restenosis occurs in second generation DES, the current data suggest a different time course and different morphological characteristics from first generation. Future prospective studies should evaluate the relationship between ISR morphology, time course and clinical events.