Duration of Dual Anti-Platelet Therapy Post-Percutaneous Intervention: Is There A Correct Amount of Time?

Molecular Ultrasound Imaging of αvβ3-Integrin Expression in Carotid Arteries of Pigs After Vessel Injury

OBJECTIVES

Interventions such as balloon angioplasty can cause vascular injury leading to platelet activation, thrombus formation, and inflammatory response. This induces vascular smooth muscle cell activation and subsequent re-endothelialization with expression of αvβ3-integrin by endothelial cells and vascular smooth muscle cell. Thus, poly-N-butylcyanoacrylate microbubbles (MBs) targeted to αvβ3-integrin were evaluated for monitoring vascular healing after vessel injury in pigs using molecular ultrasound imaging.

MATERIALS AND METHODS

Approval for animal experiments was obtained. The binding specificity of αvβ3-integrin-targeted MB to human umbilical vein endothelial cells was tested with fluorescence microscopy. In vivo imaging was performed using a clinical ultrasound system and an 8-MHz probe. Six mini pigs were examined after vessel injury in the left carotid artery. The right carotid served as control. Uncoated MB, cDRG-coated MB, and αvβ3-integrin-specific cRGD-coated MB were injected sequentially. Bound MBs were assessed 8 minutes after injection using ultrasound replenishment analysis. Measurements were performed 2 hours, 1 and 5 weeks, and 3 and 6 months after injury. In vivo data were validated by immunohistochemistry.

RESULTS

Significantly stronger binding of cRGD-MB than MB and cDRG-MB to human umbilical vein endothelial cells was found (P < 0.01). As vessel injury leads to upregulation of αvβ3-integrin, cRGD-MBs bound significantly stronger (P < 0.05) in injured carotid arteries than at the counter side 1 week after vessel injury and significant differences could also be observed after 5 weeks. After 3 months, αvβ3-integrin expression decreased to baseline and binding of cRGD-MB was comparable in both vessels. Values remained at baseline also after 6 months.

CONCLUSIONS

Ultrasound imaging with RGD-MB is promising for monitoring vascular healing after vessel injury. This may open new perspectives to assess vascular damage after radiological interventions.

Bilirubin coating attenuates the inflammatory response to everolimus-coated stents

The aim of this study was to evaluate the effects of bilirubin- and/or everolimus (EVL)-coated stents to prevent arterial neointimal hyperplasia and inflammation in vitro and in vivo. The stents were prepared by spray coating bare metal stents (BMS) with bilirubin and/or EVL. Study groups were divided into (1) BMS, (2) bilirubin-coated stents (BES), (3) commercialized stents (Synergy™; EES), and (4) bilirubin/EVL-coated stents (B-EES). The coating thickness and drug release rates were comparable to previous reports (i.e., <4 µm thickness and 50% drug release in 7 days). Smooth muscle cell migration was inhibited in both EVL-containing groups (20.5 ± 3.80% in EES and 18.4 ± 2.55% in B-EES) compared to the non-EVL-containing groups (78.0 ± 6.41% in BMS and 76.1 ± 4.88% in BES) (n = 10, p < 0.05). Stents were randomly implanted to 40 coronary arteries in 20 pigs and subjected to various analyses after 4 weeks of implantation. As results, the inflammation score was dramatically increased in the EES group (2.1 ± 0.42) compared to that of the other groups (1.5 ± 0.55, 1.3 ± 0.23, and 1.5 ± 0.27 for BMS, BES, and B-EES, respectively, n = 10, p < 0.05). Immunofluorescence analysis revealed that inflammation was prevented in the bilirubin-containing groups (BES and B-EES). However, the percent area of restenosis was decreased in the EVL-containing groups (20.5 ± 4.11% for EES and 18.4 ± 3.61% for B-EES) compared to the non-EVL-containing groups (32.3 ± 6.41% for BMS and 29.6 ± 5.95% for BES, n = 10, p < 0.05). The percent areas of restenosis determined by histopathology, optical coherence tomography, and micro-computed tomography were consistent. In addition, the stent was barely covered in the EES and B-EES groups at 4 weeks postimplantation. These dual drug-coated stents may be especially beneficial to patients who have an increased risk of inflammation. These stents have great potential for use in cardiovascular applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1486-1495, 2018.

Duration of Dual Antiplatelet Therapy After Drug-Eluting Stent Implantation in Patients With and Without Acute Coronary Syndrome: A Systematic Review of Randomized Controlled Trials

In this systemic review we evaluated the efficacy and safety of long duration dual anti-platelet therapy (DAPT) (L-DAPT) compared with short duration DAPT (S-DAPT) after drug-eluting stent (DES) implantation in patients who presented with or without acute coronary syndromes (ACS). We identified 8 randomized controlled trials in which 30,975 patients were randomized to S-DAPT versus L-DAPT (12,421 ACS and 18,554 non-ACS). Short duration dual anti-platelet therapy was associated with an increase in target vessel revascularization (TVR) in ACS patients, but the difference was not significant for non-ACS patients (odds ratio [OR] 5.04 [95% CI, 1.28-19.76], and OR, 0.89 [95% CI, 0.51-1.55], respectively). The risk of cardiac mortality was not significantly different with S-DAPT and L-DAPT for ACS (OR, 1.69 [95% CI, 0.82-3.50]) and non-ACS patients (OR, 0.89 [95% CI, 0.57-1.37]). For all cause mortality, myocardial infarction, and stent thrombosis, most of the events were derived from the DAPT study, thus a meta-analysis was not performed for these end points. Based on our review of the literature, we conclude that S-DAPT was associated with higher rates of stent thrombosis and myocardial infarction, and non-significant differences in all-cause mortality, with no significant interactions according to ACS vs non-ACS. However, in non-ACS patients, the benefit-risk profile favored S-DAPT, with lower all-cause mortality, whereas the trends were reversed in ACS. Additional studies are required to determine if the benefit-risk profile of S-DAPT vs L-DAPT varies according to clinical syndrome.

Stirred, shaken, or stagnant: What goes on at the blood-biomaterial interface

There is a widely recognized need to improve the performance of vascular implants and external medical devices that come into contact with blood by reducing adverse reactions they cause, such as thrombosis and inflammation. These reactions lead to major adverse cardiovascular events such as heart attacks and strokes. Currently, they are managed therapeutically. This need remains unmet by the biomaterials research community. Recognized stagnation of the blood-biomaterial interface research translates into waning interest from clinicians, funding agencies, and practitioners of adjacent fields. The purpose of this contribution is to stir things up. It follows the 2014 BloodSurf meeting (74th International IUVSTA Workshop on Blood-Biomaterial Interactions), offers reflections on the situation in the field, and a three-pronged strategy integrating different perspectives on the biological mechanisms underlying blood-biomaterial interactions. The success of this strategy depends on reengaging clinicians and on the renewed cooperation of the funding agencies to support long-term efforts.

Secreted Matrix Metalloproteinase-9 of Proliferating Smooth Muscle Cells as a Trigger for Drug Release from Stent Surface Polymers in Coronary Arteries

Cardiovascular diseases are the leading causes of death in industrialized countries. Atherosclerotic coronary arteries are commonly treated with percutaneous transluminal coronary intervention followed by stent deployment. This treatment has significantly improved the clinical outcome. However, triggered vascular smooth muscle cell (SMC) proliferation leads to in-stent restenosis in bare metal stents. In addition, stent thrombosis is a severe side effect of drug eluting stents due to inhibition of endothelialization. The aim of this study was to develop and test a stent surface polymer, where cytotoxic drugs are covalently conjugated to the surface and released by proteases selectively secreted by proliferating smooth muscle cells. Resting and proliferating human coronary artery smooth muscle cells (HCASMC) and endothelial cells (HCAEC) were screened to identify an enzyme exclusively released by proliferating HCASMC. Expression analyses and enzyme activity assays verified selective and exclusive activity of the matrix metalloproteinase-9 (MMP-9) in proliferating HCASMC. The principle of drug release exclusively triggered by proliferating HCASMC was tested using the biodegradable stent surface polymer poly-l-lactic acid (PLLA) and the MMP-9 cleavable peptide linkers named SRL and AVR. The specific peptide cleavage by MMP-9 was verified by attachment of the model compound fluorescein. Fluorescein release was observed in the presence of MMP-9 secreting HCASMC but not of proliferating HCAEC. Our findings suggest that cytotoxic drug conjugated polymers can be designed to selectively release the attached compound triggered by MMP-9 secreting smooth muscle cells. This novel concept may be beneficial for stent endothelialization thereby reducing the risk of restenosis and thrombosis.

Coronary Atherosclerosis: Pathophysiologic Basis for Diagnosis and Management

Coronary atherosclerosis is a long lasting and continuously evolving disease with multiple clinical manifestations ranging from asymptomatic to stable angina, acute coronary syndrome (ACS), heart failure (HF) and sudden cardiac death (SCD). Genetic and environmental factors contribute to the development and progression of coronary atherosclerosis. In this review, current knowledge related to the diagnosis and management of coronary atherosclerosis based on pathophysiologic mechanisms will be discussed. In addition to providing state-of-the-art concepts related to coronary atherosclerosis, special consideration will be given on how to apply data from epidemiologic studies and randomized clinical trials to the individual patient. The greatest challenge for the clinician in the twenty-first century is not in absorbing the fast accumulating new knowledge, but rather in applying this knowledge to the individual patient.