fibrin and nitinol

Mechanism of femoropopliteal in-stent restenosis has been underappreciated.. The aim of this animal study was to elucidate vascular response after femoropopliteal bare nitinol self-expanding stents (SESs) implantation.. Misago, Smart Flex, or Innova stent was randomly implanted in 36 swine femoropopliteal arteries. At week 4, quantitative vessel analysis (QVA) was performed on 36 legs, of which 18 underwent histological evaluation after angiography. The remaining 18 legs underwent QVA and histological evaluation at week 13.. Fibrin deposition was excessive at week 4. Internal elastic lamina (IEL) progressively enlarged over time, and vessel injury developed from mild level at week 4 to moderate level at week 13. Vessel inflammatory reaction was mild to moderate at week 4, and was moderate to severe at week 13. Increased fibrin deposition was an early-acting, IEL enlargement and increased vessel inflammation were long-acting, and increased vessel injury and giant cells infiltration were late-acting contributors to neointimal hyperplasia (NIH). Stent type altered time-dependent process of vessel injury, vessel inflammation, eosinophils and giant cells infiltration. Misago had less fibrin deposition and vessel enlargement, and less progressive vessel injury, vessel inflammation, and eosinophils and giant cells infiltration. Net lumen as assessed by percent diameter stenosis or minimum lumen diameter was preserved with Misago, but was not preserved with the other stents.. In the context of bare nitinol SES platform with less progressive mechanical stress and inflammatory reaction, the advantage of less NIH outweighed the disadvantage of less vessel enlargement, leading to net lumen preservation.

Topics: Alloys; Animals; Femoral Artery; Fibrin; Prosthesis Design; Stents; Swine; Treatment Outcome

Covered stents have been demonstrated to reduce restenosis; however, the membrane's limited biocompatibility can still lead to thrombus formation. To obtain optimal surface hemocompatibility, endothelialization of the luminal surface has been proposed. However, the effect of delivery procedures, such as crimping and balloon dilatation, on the endothelial layer has not been quantified. This study investigated the impact of such procedures on endothelialized covered stents in vitro.. Using an injection molding technique, bare metal stents were covered with fibrin subsequently, endothelialized and conditioned in a bioreactor under arterial pressure (80-120 mmHg) and shear stress (1 Pa). For each set of experiments, three covered stents were prepared, one being subjected to crimping alone, one to crimping followed by balloon dilatation and one serving as control. The experiment was repeated three times. The endothelial coverage was quantified by scanning electron microscopy (SEM). The functionality of the endothelium after exposure to platelet-rich plasma was evaluated by immunohistochemistry and SEM.. The mean endothelial coverage of control, crimped, crimped and balloon-dilated stents was 87.6, 80.1 and 52.1%, respectively, indicating that endothelial cells detached significantly not after crimping (P = 0.465) but following balloon dilatation (P < 0.001). The cells present on the stent's surface, either after crimping or crimping followed by balloon dilatation, expressed eNOS and CD31 and exhibited no platelet adhesion.. The simulated delivery procedure resulted in the retention of viable cells on more than half of the luminal surface. The main damage to the layer occurred during balloon dilatation.

Topics: Alloys; Angioplasty, Balloon; Animals; Biocompatible Materials; Constriction, Pathologic; Dilatation; Endothelium, Vascular; Fibrin; Gels; Humans; In Vitro Techniques; Microscopy, Electron, Scanning; Models, Cardiovascular; Self Expandable Metallic Stents; Thrombosis

Because of its low profile and biologically inert behavior, thin film nitinol (TFN) is ideally suited for use in construction of endovascular devices. We have developed a surface treatment for TFN designed to minimize platelet adhesion by creating a superhydrophilic surface. The hemocompatibility of expanded polytetrafluorethylene (ePTFE), untreated thin film nitinol (UTFN), and a surface treated superhydrophilic thin film nitinol (STFN) was compared using an in vitro circulation model with whole blood under flow conditions simulating a moderate arterial stenosis. Scanning electron microscopy analysis showed increased thrombus on ePTFE as compared to UTFN or STFN. Total blood product deposition was 6.3 ± 0.8 mg/cm(2) for ePTFE, 4.5 ± 2.3 mg/cm(2) for UTFN, and 2.9 ± 0.4 mg/cm(2) for STFN (n = 12, p < 0.01). ELISA assay for fibrin showed 326 ± 42 μg/cm(2) for ePTFE, 45.6 ± 7.4 μg/cm(2) for UTFN, and 194 ± 25 μg/cm(2) for STFN (n = 12, p < 0.01). Platelet deposition measured by fluorescent intensity was 79,000 20,000 AU/mm(2) for ePTFE, 810 ± 190 AU/mm(2) for UTFN, and 1600 ± 25 AU/mm(2) for STFN (n = 10, p < 0.01). Mass spectrometry demonstrated a larger number of proteins on ePTFE as compared to either thin film. UTFN and STFN appear to attract significantly less thrombus than ePTFE. Given TFN's low profile and our previously demonstrated ability to place TFN covered stents in vivo, it is an excellent candidate for use in next-generation endovascular stents grafts.

Topics: Alloys; Blood Platelets; Blood Proteins; Coronary Stenosis; Fibrin; Hemorheology; Humans; Mass Spectrometry; Materials Testing; Microscopy, Electron, Scanning; Microscopy, Fluorescence; Thrombosis

Dysfunction of haemodialysis catheters is most commonly due to a narrowing of the catheter lumen and/or formation of a fibrin sheath around the catheter tip. Reported methods for restoring patency of the catheter lumen include passage of a J-tipped guide wire, passage of a biopsy brush through the catheter, or infusion of a thrombolytic agent into the catheter. While these methods are often effective, they suffer from several limitations. We present a minimally invasive technique to remove thrombi and debris from within the lumen of a partially thrombosed haemodialysis catheter while simultaneously stripping the fibrous sheath.. A 0.089 cm nitinol wire is bent to create a loop, which is then inserted via the catheters. Upon exiting the lumen of the catheters, the nitinol wire forces a snare open, which disrupts the fibrin sheath and catches intraluminal thrombi and debris. The technique requires no anaesthesia or recovery time.. Initial clinical success in our series was achieved in all patients (7/7) as evidenced by restoration of target flow rates on subsequent haemodialysis. None of the patients experienced any complications as a result of the procedure. The catheter 2-, 4-, and 6-week primary success rates were 100% (8/8), 100% (8/8), and 100% (8/8) respectively with a mean duration of 17.1 weeks (range 8-40 weeks).. The internal snare technique is an effective, inexpensive and minimally invasive approach to restoring patency to failed central venous access catheters.

Topics: Alloys; Blood Coagulation; Catheterization, Central Venous; Catheters, Indwelling; Elasticity; Fibrin; Humans; Renal Dialysis; Thrombosis; Vascular Patency

Percutaneous transluminal renal angioplasty and stent placement with use of a coronary protection device was performed in a total of four patients with hypertension (n = 4) and/or renal insufficiency (n = 3) referred for revascularization of five renal arteries. Renal revascularization was successful in all five renal arteries (100%), but renal revascularization under protection by the FilterWire EX was achieved in only three of five renal arteries (60%). In one of these three, only a suboptimal seal was achieved between the vessel wall and the filter basket. Nevertheless, use of the device was safe and fibrin and/or cholesterol fragments were retrieved from three renal arteries. The FilterWire EX needs to be modified for the renal circulation to achieve the full theoretical advantages of these systems in this vascular bed.

Topics: Aged; Aged, 80 and over; Alloys; Angioplasty, Balloon; Cholesterol; Embolism; Female; Fibrin; Filtration; Humans; Hypertension; Male; Middle Aged; Polyurethanes; Renal Artery Obstruction; Renal Insufficiency; Retrospective Studies; Stents; Treatment Outcome

The authors assess a new ePTFE-nitinol stent for its long-term patency, healing, and properties of endothelialization.. Adult greyhounds (n = 18) underwent bilateral iliofemoral placement of an endoprosthesis (Hemobahn) consisting of a nitinol stent lined with an ultrathin expanded polytetrafluoroethylene (ePTFE) material. Histologic and quantitative morphometric analyses were performed on devices explanted at 2 weeks and 1, 3, 6, and 12 months. The source of endothelialization was examined in four additional devices modified by sealing either the proximal and distal ends or the entire graft with poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), a nonporous laminate to prevent potential transgraft endothelial cell migration.. Device patency assessed with both intravascular ultrasound and histologic study showed minimal arterial stenosis, irrespective of implant duration. The neointima at less than 3 months consisted of fibrin and inflammatory infiltrate; at later time points, it was composed of mostly smooth muscle cells. Flow surfaces were more than 75% endothelialized by 3 months, which was nearly complete by 6 months. Modified endoprostheses entirely enveloped with FEP resulted in endothelialization of only the proximal and distal ends; the middle regions showed nonocclusive thrombi. Conversely, devices wrapped proximally and distally showed nearly complete endothelialization.. This ePTFE-nitinol endoprosthesis demonstrated long-term patency at up to 1 year after implantation and showed early and nearly complete endothelialization by 6 months. The design promoted rapid endothelialization of flow surfaces, particularly in the midregion of the device possibly by transgraft migration.

Topics: Alloys; Animals; Blood Vessel Prosthesis; Cell Movement; Dogs; Endothelium, Vascular; Female; Femoral Artery; Fibrin; Follow-Up Studies; Graft Occlusion, Vascular; Hemorheology; Iliac Artery; Image Processing, Computer-Assisted; Male; Microscopy, Electron, Scanning; Muscle, Smooth, Vascular; Polytetrafluoroethylene; Prosthesis Design; Stents; Surface Properties; Tunica Intima; Ultrasonography, Interventional; Vascular Patency; Wound Healing