Preclinical safety and efficacy evaluation of the Pipeline Vantage Embolization Device with Shield Technology.

BACKGROUND: The Pipeline Vantage Embolization Device with Shield Technology is a next generation flow diverter developed to improve aneurysm occlusion and implant endothelialization in addition to lowering thrombogenicity. We report here the in vivo biocompatibility and in vitro hemocompatibility performance of the Pipeline Vantage Embolization Device with Shield Technology (Vantage) compared with the Pipeline Flex Embolization Device (Flex). METHODS: Biocompatibility (via histology), aneurysm occlusion and vessel patency (via angiography), and endothelial coverage (via scanning electron microscopy (SEM)) for the Vantage and Flex devices were assessed in the rabbit elastase aneurysm model at 90 days (n=29) and 180 days (n=27). In vitro thrombogenicity for Flex and Vantage (n=16) was assessed using a human blood flow loop model at low heparin concentration (0.6 U/mL) with thrombin generation, platelet activation and thrombus visualization as outputs. RESULTS: Raymond Roy Occlusion Classification grade 1 was higher for Vantage (61%) compared with Flex (46%), but was not statistically significant (p>0.05). All branch vessels were patent. Histological measures for both devices were similar (p>0.05). Endothelial coverage of the implant was significantly better for Vantage compared with Flex (p<0.05). In vitro measurements of thrombin generation (thrombin-antithrombin complex (µg/mL): Vantage 0.49±0.45; Flex 10.57±9.84) and platelet activation (ß-thromboglobulin (IU/µl): Vantage 0.41±0.19; Flex 4.14±2.38) were both statistically lower (p<0.05) for Vantage compared with Flex. High resolution microscopy showed less accumulation of thrombus on Vantage as compared with Flex. CONCLUSION: Vantage improved aneurysm occlusion and implant endothelialization and had significantly lower thrombogenicity as compared with Flex, while preserving the biocompatibility safety profile of Flex.

Human aortic endothelial cell response to 316L stainless steel material microstructure.

The role of metal microstructure (e.g. grain sizes) in modulating cell adherence behavior is not well understood. This study investigates the effect of varying grain sizes of 316L stainless steel (SS) on the attachment and spreading of human aortic endothelial cells (HAECs). Four different grain size samples; from 16 to 66 microm (ASTM 9.0-4.9) were sectioned from sheets. Grain structure was revealed by polishing and etching with glycergia. Contact angle measurement was done to assess the hydrophilicity of the specimens. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the roughness and surface chemistry of the specimens. Cells were seeded on mechanically polished and chemically etched specimens followed by identification of activated focal adhesion sites using fluorescently tagged anti-pFAK (phosphorylated focal adhesion kinase). The 16 microm grain size etched specimens had significantly (P < 0.01) higher number of cells attached per cm(2) than other specimens, which may be attributed to the greater grain boundary area and associated higher surface free energy. This study shows that the underlying material microstructure may influence the HAEC behavior and may have important implications in endothelialization.

Thermal processing and characterization of 316LVM cardiovascular stent.

In the current investigation, annealing was employed as a means to improve the mechanical performance of 316LVM coronary stents. Two different temperatures (1000 degrees C and 1150 degrees C) were explored for the thermal processing of the device. Acid pickling was done as a pre-annealing step to remove the debris and slag material attached to the stent after laser cutting. Post annealing operation involved the electrochemical polishing of the device which was also a parameter for assessment of the feasibility of the annealing process. Microstructural characterization, balloon expandability and tensile testing of the stents were performed to characterize the properties after thermal treatment. A fine grained austenitic structure with marked improvement in the % elongation (>40%) could be achieved after annealing the stents at 1000 degrees C. Balloon expandability tests of the stents annealed at 1000 degrees C indicated that the device was implantable.

Surface conditioning of 316LVM slotted tube cardiovascular stents.

The surface quality of coronary stents has a significant influence on its biocompatibility. Therefore, surface polishing is of paramount importance in the production and application of stents. In the present study, electropolishing is performed on 316LVM steel slotted tube coronary stents. Additionally, acid pickling, as a pretreatment of electropolishing, is also conducted. Gravimetric analysis of the stents (weight loss and strut width change) in the process of acid pickling and electropolishing are done. Qualitative roughness measurements are made to evaluate the stent surface. Electropolished stents are passivated causing chromium enrichment on the surface of the material, thereby enhancing its corrosion resistance. Passivated and electropolished samples are examined using energy dispersive spectrometry. Balloon expanded and crimped profiles of the passivated stents are qualitatively analyzed.