nitinol and Thrombosis

In patients with non-valvular atrial fibrillation, efficacy of stroke prevention with oral anticoagulant therapy has been proved. Despite their high risk for thromboembolic events, there are substantial numbers of patients who are not candidates for long-term oral anticoagulant therapy, therefore the interest in alternative treatment strategies are in focus these days. The most common place within the heart for thrombus formation in patients with non-valvular atrial fibrillation is the left atrial appendage. Two devices specifically designed for percutaneous left atrial appendage closure are currently available in Europe: the WATCHMAN LAA system (Atritech, Inc) and the AMPLATZER Cardiac Plug (AGA Medical Corporation). Although present trial results (PLAATO, PROTECT AF) suggest that LAA closure may be performed at acceptable safety and it may reduce the long-term stroke risk, available data are still very limited. At present these procedures may be an acceptable alternative in selected high-risk patients with non-valvular atrial fibrillation who are not or suboptimal candidates for oral anticoagulant therapy. On 28. January, 2010 we performed the first three successful percutaneous left atrial appendage closure procedures in Gottsegen György Hungarian Institute of Cardiology in Hungary.

Topics: Administration, Oral; Aged; Alloys; Anticoagulants; Atrial Appendage; Atrial Fibrillation; Cardiac Surgical Procedures; Clinical Trials as Topic; Contraindications; Echocardiography, Transesophageal; Female; Heart Diseases; Humans; Hungary; Male; Middle Aged; Prosthesis Design; Radiography; Risk Assessment; Risk Factors; Septal Occluder Device; Stents; Stroke; Thoracoscopy; Thrombosis; Treatment Outcome

Significantly improved long-term patency can be achieved with transjugular intrahepatic portosystemic shunt (TIPS) endografts compared to conventional bare stents. In the USA, approximately 80% of TIPS procedures are performed using these devices. The phenomenon of early shunt thrombosis with TIPS created with bare stent TIPS, attributed to biliary fistulae, is seldom observed in patients with TIPS endografts. Intrashunt stenoses within the polytetrafluoroethylene-lined conduit are also rare. However, as with shunts created with bare stents, distinct patterns of dysfunction can occur with TIPS endografts. Some of these are inherent to the learning curve of placing these devices and others are secondary to device design. The interventional radiologist needs to be aware of these patterns of shunt dysfunction and have a systematic approach to their management.

Topics: Alloys; Biliary Fistula; Humans; Hypertension, Portal; Magnetic Resonance Imaging; Polytetrafluoroethylene; Portasystemic Shunt, Transjugular Intrahepatic; Portography; Prosthesis Design; Radiography, Interventional; Stents; Thrombosis; Treatment Outcome

To evaluate mid-term primary patency of the femoral artery stenting in correlation with usCRP level and characteristics of the population, morphological aspect of the lesions and interventional techniques.. Patients were prospectively included in a multicenter study (18 centers in France) after stenting (SMART, Cordis Johnson & Johnson, Issy-les-Moulineaux, France) of the superficial femoral artery (SFA). Inclusion and exclusion criteria were based on recommendations and every day practice of the centers.. Thus 255 patients (183 men; mean age: 69 years; range 44-92) were included. Technical success of the SFA stenting was 100% without any complications and primary angiographic success 97%. usCRP level increased significantly (p < 0.05) between before and 24h after SFA stenting. In the subgroup of patients without initial inflammation (n = 157), usCRP increased significantly (p < 0.05) in the group of patient with initial thrombosis and additional intervention (graft, amputation, angioplasty on other arterial bed) in the same procedure compared to the remaining patients. Restenosis rate was 12.4% (26/209 patients) at 7 ± 2 months. Before stenting, usCRP level was not predictive of a restenosis, whereas after stenting, an increase of the 24h usCRP level was significantly higher in the subgroup of patient with an occlusion at mid-term (8 patients; p < 0.05).. This study demonstrated good patency at 7 months of SFA stenting with nitinol SMART with an increase of the usCRP level 24h after stenting in favour of the presence of an occlusion at mid-term follow-up.

Topics: Adult; Aged; Aged, 80 and over; Alloys; Angiography; Angioplasty; Arterial Occlusive Diseases; C-Reactive Protein; Female; Follow-Up Studies; Humans; Intermittent Claudication; Ischemia; Leg; Magnetic Resonance Angiography; Male; Middle Aged; Prospective Studies; Prosthesis Failure; Recurrence; Risk Factors; Stents; Thrombosis; Tomography, X-Ray Computed; Vascular Patency

To report the results of a two-center study of endovascular abdominal aortic aneurysm (AAA) exclusion using a polyester-covered nitinol stent-graft.. Candidates were evaluated with arteriography and computed tomography. Criteria for endovascular therapy were a proximal aortic neck > 10 mm in length and < 25 mm in diameter, no bilateral internal iliac artery involvement in the aneurysm, no markedly tortuous common iliac arteries (CIAs) or CIAs < 7 mm in diameter, and no superior mesenteric artery occlusive disease. Patients were treated with the Mialhe Stentor and Vanguard stent-grafts in either tube or bifurcated versions.. Between August 1994 and November 1996, 149 patients (mean age 67 years, range 49 to 90) were admitted to the study. Overall primary technical success (aneurysm exclusion without endoleak) was 87% (130 patients): 78% (7 patients) for tube grafts and 88% (123 patients) for bifurcated endografts. The rate of local, remote, or systemic complications was 10.8%, with a 30-day mortality rate of 0.7%. During an average 13.5-month follow-up, there were no late deaths. Four of 20 endoleaks sealed spontaneously, 14 were treated with endoluminal techniques, and 2 remain untreated by patient request. Three graft limb thromboses occurred; one was treated surgically, one with lytic therapy, and one was untreated. Secondary patency was 96%.. Endoluminal repair of infrarenal AAAs using straight or bifurcated grafts is a feasible alternative to conventional surgical repair. Longer follow-up and more experience with refined endograft models will elucidate the durability of this endovascular approach to treating AAAs.

Topics: Aged; Aged, 80 and over; Alloys; Aortic Aneurysm, Abdominal; Aortography; Blood Vessel Prosthesis; Follow-Up Studies; Germany; Humans; Image Processing, Computer-Assisted; Middle Aged; Postoperative Complications; Prospective Studies; Prosthesis Failure; Reoperation; Stents; Survival Rate; Thrombosis; Tomography, X-Ray Computed

Inferior vena cava (IVC) filters should be removed when no longer needed, given their association with complications such as thrombosis of the IVC and lower extremities, fracture, migration, and growth into adjacent structures. While this is generally straightforward in the setting of retrievable filters, permanent filters present more of a challenge. In fact, many operators will not attempt to do so for fear of intraprocedural complications, among them, filter fracture and fragment embolization. Despite this, leaving the filters

Topics: Embolization, Therapeutic; Humans; Lower Extremity; Thrombosis; Vena Cava Filters

We studied the effect of nitinol, the most prevalent material for endovascular stents, on metabolic and coagulation activity of a primary culture of human umbilical vein endothelial cells (HUVEC). Metabolic activity was evaluated using MTS-test and by the level of stable NO metabolites in the conditioned medium, coagulation activity was assessed by activity of von Willebrand factor (vWF) and levels of plasminogen activator inhibitor-1 (PAI-1) and soluble endothelial protein C receptors (sEPCR). Exposure to nitinol reduced metabolic activity of the cell culture by 11.1% in comparison with the control (p<0.001). Although absolute activity of vWF and absolute level of sEPCR were elevated, incubation with nitinol did not lead to a statistically significant elevation of these parameters in comparison with the control, which can indicate the absence of substantial hypercoagulation effects of nitinol.

Topics: Alloys; Blood Coagulation; Blood Coagulation Factors; Cells, Cultured; Endothelial Protein C Receptor; Endothelium, Vascular; Human Umbilical Vein Endothelial Cells; Humans; Plasminogen Activator Inhibitor 1; Thrombosis; von Willebrand Factor

 Patients with postthrombotic syndrome (PTS) treated with stents are at risk of stent thrombosis (ST). The incidence of ST in the presence and absence of anticoagulation therapy (AT) is unknown. Risk factors are not well understood..  From the prospective Swiss Venous Stent registry, we conducted a subgroup analysis of 136 consecutive patients with PTS. Incidence of ST was estimated from duplex ultrasound or venography, and reported for the time on and off AT. Baseline, procedural, and follow-up data were evaluated to identify factors associated with ST..  Median follow-up was 20 (interquartile range [IQR] 9-40) months. AT was stopped in 43 (32%) patients after 12 (IQR 6-14) months. Cumulative incidence of ST was 13.7% (95% confidence interval [CI] 7.8-19.6%) and 21.2% (95% CI 13.2-29.2%) during the first 6 and 36 months, respectively. The time-adjusted incidence rate was 11.2 (95% CI 7.7-16.2) events per 100 patient-years, 11.3 (95% CI 7.3-17.3) for the period on, and 11.2 (95% CI 5.3-23.6) for the period off AT. May-Thurner syndrome (MTS) was associated with decreased incidence of ST (hazard ratio [HR] 0.37, 95% CI 0.15-0.91), whereas age < 40 years (HR 2.26, 95% CI 1.03-4.94), stents below the common femoral vein (HR 3.03, 95% CI 1.28-7.19), and postthrombotic inflow veins (HR 2.92, 95% CI 1.36-6.25) were associated with increased incidence..  The 6-month incidence of ST was considerably high. Beyond 6 months, consecutive annual incidence rates persisted at 4.1 and 3.4% per year thereafter. Patients with higher incidence of ST were younger, had stents below the common femoral vein, postthrombotic leg inflow veins, and less often MTS. Incidence rates for the period on and off AT must be interpreted with caution..  The study is registered on the National Institutes of Health Web site (ClinicalTrials.gov; identifier NCT02433054).

Topics: Adult; Alloys; Anticoagulants; Endovascular Procedures; Female; Femoral Vein; Fibrinolytic Agents; Follow-Up Studies; Humans; Iliac Vein; Incidence; Male; Middle Aged; Phlebography; Postthrombotic Syndrome; Registries; Risk Factors; Stents; Switzerland; Thrombosis; Treatment Outcome; Vena Cava, Inferior

Metallic Zn alloys have recently gained interest as potential candidates for developing platforms of bioresorbable vascular stents (BVS). Previous studies revealed that Mg alloys used for BVS can degrade too early, whereas PLLA materials may fail to provide effective scaffolding properties. Here we report on results of a new bioresorbable, metallic stent made from a Zn-Ag alloy studied in a porcine animal model of thrombosis and restenosis. While the tensile strength (MPa) of Zn-3Ag was higher than that of PLLA and resembled Mg's (WE43), fracture elongation (%) of Zn-3Ag was much greater (18-fold) than the PLLA's or Mg alloy's (WE43). Zn-3Ag exposed to HAoSMC culture medium for 30 days revealed degradation elements consisting of Zn, O, N, C, P, and Na at a 6 nm surface depth. Platelet adhesion rates and blood biocompatibility did not differ between Zn-3Ag, PLLA, Mg (WE43), and non-resorbable Nitinol (NiTi) stent materials. Balloon-expandable Zn-3Ag alloy BVS implanted into iliofemoral arteries of 15 juvenile domestic pigs were easily visible fluoroscopically at implantation, and their bioresorption was readily detectable via X-ray over time. Histologically, arteries with Zn-3Ag BVS were completely endothelialized, covered with neointima, and were patent at 1, 3, and 6 months follow-up with no signs of stent thrombosis. Zn-3Ag alloy appears to be a promising material platform for the fabrication of a new generation of bioresorbable vascular stents.

Topics: Absorbable Implants; Alloys; Animals; Drug-Eluting Stents; Polyesters; Swine; Thrombosis; Zinc

Endovascular treatment of carotid artery stenosis is a valuable alternative to open surgery, and the evolution of stent materials and cerebral protection devices significantly decreased postoperative neurological complications. Among these, the introduction of nitinol double-layer micromesh stent seems to guarantee a reduced perioperative and postoperative cerebral embolization. Long-term results are however still not available to make a global evaluation of these stents. We present the case of a 66-year-old female patient treated for asymptomatic carotid stenosis complicated by a symptomatic partial stent thrombosis occurred three months after carotid artery stenting.

Topics: Aged; Alloys; Anticoagulants; Asymptomatic Diseases; Carotid Stenosis; Computed Tomography Angiography; Embolic Protection Devices; Endovascular Procedures; Female; Humans; Platelet Aggregation Inhibitors; Prosthesis Design; Stents; Surgical Mesh; Thrombosis; Time Factors; 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

To report the real-world incidence and risk factors of stent thrombosis in the aortoiliac and femoropopliteal arteries in case of bare nitinol stent (BNS) or covered nitinol stent (CNS) placement from a single-centre retrospective audit.. Medical records of consecutive patients treated with peripheral stent placement for claudication or critical limb ischemia were audited for definite stent thrombosis defined as imaging confirmed stent thrombosis that presented as acute limb-threatening ischemia. Cases were stratified between aortoiliac and femoropopliteal anatomy. Cox regression analysis was employed to adjust for baseline clinical and procedural confounders and identify predictors of stent thrombosis and major limb loss.. 256 patients (n = 277 limbs) were analysed over a 5-year period (2009-2014) including 117 aortoiliac stents (34 CNS; 12.8 ± 5.0 cm and 83 BNS; 7.8 ± 4.0 cm) and 160 femoropopliteal ones (60 CNS; 21.1 ± 11.0 cm and 100 BNS; 17.5 ± 11.9 cm). Median follow-up was 1 year. Overall stent thrombosis rate was 6.1% (17/277) after a median of 43 days (range 2-192 days) and affected almost exclusively the femoropopliteal segment (12/60 in the CNS cohort vs. 4/100 in the BNS; p = 0.001). Annualized stent thrombosis rates (per 100 person-years) were 12.5% in case of CNS and 1.4% in case of BNS (HR 6.3, 95% CI 2.4-17.9; p = 0.0002). Corresponding major amputations rates were 8.7 and 2.5%, respectively (HR 4.5, 95% CI 2.7-27.9; p = 0.0006). On multivariable analysis, critical leg ischemia and CNS placement were the only predictors of stent thrombosis. Diabetes, critical leg ischemia, femoropopliteal anatomy, long stents and CNS were independent predictors of major amputations.. Placement of long femoropopliteal covered nitinol stents is associated with an increased incidence of acute stent thrombosis and ensuing major amputation. Risks are significantly lower in the aortoiliac vessels and with use of bare nitinol stents.

Topics: Acute Disease; Aged; Alloys; Amputation, Surgical; Aorta; Causality; Comorbidity; Constriction, Pathologic; Extremities; Female; Femoral Artery; Follow-Up Studies; Humans; Incidence; Intermittent Claudication; Ischemia; Male; Peripheral Arterial Disease; Popliteal Artery; Prosthesis Design; Prosthesis Failure; Retrospective Studies; Risk Factors; Stents; Thrombosis; Time Factors; Treatment Outcome; Vascular Patency

We sought to evaluate the pathologic findings of the percutaneous Parachute device implanted in patients with severe heart failure (HF).. Currently, most treatments of HF rest on optimal medical therapy with adjunctive interventional or surgical palliative treatments. One such treatment is the Parachute device, which partitions the left ventricle excluding the scarred myocardium from functioning myocardium, and has shown promise in clinical studies.. We have examined histopathologically seven cases [six males (age range 43–74 years; mean 56 years) and one female (55 years)] of Parachute device that were either retrieved at autopsy (n = 4) or during transplantation (n = 3); implant duration, 15-1,533 days.. Three patients died of cardiac causes and none died from complications. Histologic early changes (<30 days, n = 1) included adherent thrombus, with focal neutrophil infiltration and degenerating inflammatory cells. Over time (31–300 days, n = 4), there was organized thrombus and development of neoendocardial thickening especially at the free-edge of the device and its contact with the adjacent endocardium while the base of the device showed varying degrees of fibrin thrombus. The greatest organization of thrombus was observed in devices removed at >300 days (680 and 1533 days); both had fractures of the foot along with strut fracture and one had tearing of the expanded polytetrafluoroethylene.. The percutaneous Parachute device appears as a promising adjunctive treatment for patients suffering from severe HF. The pathologic changes are those of organizing thrombus with and without inflammation with minor complications of foot and strut fracture.

Topics: Adult; Aged; Alloys; Autopsy; Coronary Artery Disease; Device Removal; Equipment Design; Female; Heart Failure; Heart Transplantation; Heart-Assist Devices; Humans; Male; Middle Aged; Myocarditis; Myocardium; Severity of Illness Index; Thrombosis; Time Factors; Wound Healing

A 74-year-old woman complained of claudication due to in-stent restenosis of bare-metal stents in the right superficial femoral artery, and two Zilver PTXs were deployed. However, hemarthrosis developed, and aspirin and clopidogrel were discontinued. Thirty-six days later, she suddenly felt rest pain in her right leg. Angiography revealed total occlusion at the Zilver PTX implantation site, demonstrating late stent thrombosis. Aspiration and thrombolysis yielded adequate flow and symptom resolution. Follow-up catheterization was scheduled 6 months later. While the Zilver PTX stents were angiographically patent, angioscopy demonstrated a large red thrombus and uncovered stent struts. Therefore, dual antiplatelet therapy was continued.

Topics: Aged; Alloys; Angiography; Angioscopy; Antineoplastic Agents, Phytogenic; Drug-Eluting Stents; Female; Femoral Artery; Follow-Up Studies; Graft Occlusion, Vascular; Humans; Intermittent Claudication; Paclitaxel; Prosthesis Failure; Thrombosis; Time Factors

Persistent retrograde false lumen perfusion is a common mode of failure after thoracic endovascular aortic repair (TEVAR) for chronic dissection. Objectives were to describe a novel endovascular approach for false lumen occlusion and assess outcomes.. From 2009 to 2013, 21 patients (mean age, 64 ± 11 years) with chronic thoracoabdominal dissection underwent adjunctive false lumen embolization using covered stent devices for persistent retrograde perfusion. Eight patients had type B dissection, 13 had residual dissection after prior type A repair, and all were deemed high risk for open operation. False lumen embolization in 17 patients was an adjunct at the initial TEVAR or extension, including two as elephant trunk completion. In the other four, this was done as an isolated procedure, and three had previously undergone TEVAR sparing the celiac artery. Covered stent devices included iliac plugs in 18, nitinol embolization plugs in two, and occluded stent graft in one. More than one device was used in 15 patients.. There was one hospital death due to left subclavian artery aneurysm rupture but no patient had stroke, paraplegia, myocardial infarction, or renal failure. Mean follow-up was 25 ± 19 months. During surveillance computed tomography imaging, false lumen thrombosis was noted in all patients, but four required further embolization because the thrombosis was incomplete. Mean maximum aortic diameter decreased from 64 ± 14 to 59 ± 15 mm. There was one late death from intracranial hemorrhage and no aortic ruptures.. Adjunctive false lumen embolization with a covered stent device promotes thrombosis and remodeling after stent grafting the true lumen for chronic dissection. Further study of this strategy is warranted.

Topics: Aged; Alloys; Aortic Aneurysm, Thoracic; Aortic Dissection; Aortography; Chronic Disease; Embolization, Therapeutic; Endovascular Procedures; Female; Humans; Male; Middle Aged; Prosthesis Design; Stents; Thrombosis; Time Factors; Tomography, X-Ray Computed; Treatment Outcome; Vascular Remodeling

Most arteriovenous hemodialysis grafts fail ≤18 months after implantation, most commonly due to intimal hyperplasia at the venous anastomosis. This open prospective study compared balloon angioplasty vs nitinol stent placement in the treatment of venous anastomotic stenosis after thrombectomy of prosthetic brachial-axillary accesses.. Between February 2007 and December 2010, 61 patients with an initial thrombosis of a prosthetic brachial-axillary access were admitted to our hospital. Of these patients, 28 (46%), treated before June 2008, underwent thrombectomy plus balloon angioplasty of the venous anastomosis (group A), whereas the remaining 33 (54%) patients, who were treated after July 2008, underwent graft thrombectomy plus angioplasty with self-expanding nitinol stent placement (group B). Primary, primary-assisted, and secondary patency rates were calculated using Kaplan-Meier analysis and compared between the two groups with the log-rank test.. Primary patency was 32% at 3 months, 24% at 6 months, and 14% at 12 months in group A, and the respective values were 85%, 63% and 49% in group B. Primary patency was significantly better in group B than in group A (P < .001; log-rank test). Cumulative median patency was 60 days in group A and 260 days in group B. Patient age, sex, comorbidities, graft material, and graft age did not have prognostic significance. Primary-assisted and secondary patency rates were significantly higher in group B.. Graft thrombectomy plus angioplasty with self-expanding nitinol stent placement provides significantly higher patency rates compared with thrombectomy plus plain balloon angioplasty of the venous anastomosis.

Topics: Adult; Aged; Aged, 80 and over; Alloys; Angioplasty, Balloon; Arteriovenous Shunt, Surgical; Axillary Vein; Blood Vessel Prosthesis Implantation; Brachial Artery; Chi-Square Distribution; Female; Graft Occlusion, Vascular; Greece; Humans; Kaplan-Meier Estimate; Male; Middle Aged; Proportional Hazards Models; Prospective Studies; Prosthesis Design; Renal Dialysis; Risk Assessment; Risk Factors; Stents; Thrombectomy; Thrombosis; Time Factors; Treatment Outcome; Vascular Patency

We investigated tissue responses to endoskeleton stent grafts for saccular abdominal aortic aneurysms (AAAs) in canines. Saccular AAAs were made with Dacron patch in 8 dogs, and were excluded by endoskeleton stent grafts composed of nitinol stent and expanded polytetrafluoroethylene graft. Animals were sacrificed at 2 months (Group 1; n = 3) or 6 months (Group 2; n = 5) after the placement, respectively. The aortas embedding stent grafts were excised en bloc for gross inspection and sliced at 5 to 8 mm intervals for histopathologic evaluation. Stent grafts were patent in all except a dog showing a thrombotic occlusion in Group 2. In the 7 dogs with patent lumen, the graft overhanging the saccular aneurysm was covered by thick or thin thrombi with no endothelial layer, and the graft over the aortic wall was completely covered by neointima with an endothelial layer. Transgraft cell migration was less active at an aneurysm than at adjacent normal aorta. In conclusion, endoskeleton stent grafts over saccular aneurysms show no endothelial coverage and poor transgraft cell migration in a canine model.

Topics: Alloys; Angiography; Animals; Aortic Aneurysm, Abdominal; Cell Movement; Disease Models, Animal; Dogs; Endothelial Cells; Neointima; Polytetrafluoroethylene; Stents; Thrombosis; Tomography, X-Ray Computed; Ultrasonography

Thin film nitinol (TFN) is a novel material with which to cover stents for the treatment of a wide range of vascular disease processes. This study aimed to show that TFN, if treated to produce a super hydrophilic surface, significantly reduces platelet adhesion, potentially rendering covered stents more resistant to thrombosis compared to commercially available materials.. TFN was fabricated using a sputter deposition process to produce a 5-μ thin film of uniform thickness. TFN then underwent a surface treatment process to create a super hydrophilic layer. Platelet adhesion studies compared surface treated TFN (S-TFN) to untreated TFN, polytetrafluoroethylene, Dacron, and bulk nitinol. In vivo swine studies examined the placement of an S-TFN covered stent in a 3.5 mm diameter external iliac artery. Angiography confirmed placement, and repeat angiography was performed at 2 wk followed by post mortem histopathology.. S-TFN significantly reduced platelet adhesion without any evidence of aggregation compared with all materials studied (P < 0.05). Furthermore, in vivo swine studies demonstrated complete patency of the S-TFN covered stent at 2 wk. Post mortem histopathology showed rapid endothelialization of the S-TFN without excessive neointimal hyperplasia.. These results demonstrate that S-TFN significantly reduces platelet adhesion and aggregation compared with commercially available endograft materials. Furthermore, the hydrophilic surface may confer thromboresistance in vivo, suggesting that S-TFN is a possible superior material for covering stents.

Topics: Alloys; Angiography; Animals; Coated Materials, Biocompatible; Hydrophobic and Hydrophilic Interactions; Iliac Artery; Materials Testing; Models, Animal; Platelet Adhesiveness; Platelet Aggregation; Polyethylene Terephthalates; Polytetrafluoroethylene; Stents; Sus scrofa; Thrombosis

In the setting of ST-elevation myocardial infarction (STEMI), epicardial vasoconstriction and thrombus load may lead to stent undersizing and malapposition after primary percutaneous coronary intervention (PPCI), which can both be responsible for stent thrombosis or restenosis. Aggressive stent deployment can, on the other hand, cause distal embolisation and the no-reflow phenomenon. The purpose of our study was to evaluate the safety and feasibility of a novel self-expanding stent by assessing the clinical, angiographic and intravascular outcomes after stent deployment at three days and at six months follow-up.. This prospective, multicentre, non-randomised study enrolled 25 STEMI patients undergoing PPCI; a nitinol, self-expanding, coronary stent (STENTYS® stent; STENTYS, Paris, France) was used in all patients. Angiography and intravascular ultrasound (IVUS) or optical coherence tomography (OCT) were performed immediately after stent deployment, after three days and at six months. Primary safety endpoints were mortality, reinfarction, stent thrombosis and stroke at discharge and at six months. The primary feasibility endpoints were technical, device and procedural success, and stent apposition at three days and six months. Secondary endpoints included distal embolisation, binary restenosis, ischaemia-driven target lesion revascularisation (TLR) and late lumen loss (LLL). There were no adverse events at discharge or at six months. Technical, device and procedural success were 100%, 96% and 96%, respectively. IVUS showed a significant vasodilatation distal to the culprit lesion at three-day follow-up (+19%), with a concordant expansion of the implanted stent (+18%), p≤0.001 for both values. One case of distal embolisation was reported. There were no cases of late stent malapposition at six months. In-stent and in-segment LLL were 0.71±0.71 mm and 0.58±0.61 mm. Binary restenosis was 25%, ischaemia-driven TLR was 12%.. This study shows that the use of the STENTYS® self-expanding stent is safe and feasible in STEMI patients. Three days after the procedure, the stent expanded to the same extent as the epicardial vasodilatation and appeared completely apposed to the vessel wall. This could be of benefit in preventing stent thrombosis in the setting of STEMI.

Topics: Adult; Aged; Alloys; Angioplasty, Balloon, Coronary; Coronary Angiography; Coronary Restenosis; Embolism; Europe; Feasibility Studies; Female; Humans; Male; Middle Aged; Myocardial Infarction; Prospective Studies; Prosthesis Design; Recurrence; Stents; Thrombosis; Time Factors; Tomography, Optical Coherence; Treatment Outcome; Ultrasonography, Interventional

Biocompatibility of two multilayer coatings of (Fe3+/Hep)10 and (Fe3+/DS/Fe3+/Hep)5 was comparatively analyzed with respect to protein adsorption, leukocyte adhesion and cell-material interaction. Both of them showed significantly high albumin-to-fibrinogen adsorption ratio, suggesting good biocompatibility. Furthermore, the (Fe3+/DS/Fe3+/Hep)5 coating was found to exhibit the lowest non-specific protein adsorption due to the incorporation of dextran sulfate. Compared with uncoated Nitinol surfaces, iron-polysaccharide multilayer coating presented no deformation of leukocytes, indicating no signs of inflammatory reactions. Cell growth, cell adhesion and cell metabolic activity were all in good condition, verifying both (Fe3+/Hep)10 and (Fe3+/DS/Fe3+/Hep)5 coatings had good cytocompatibility. Therefore, iron-polysaccharides multilayer coatings had greatly improved the biocompatibility of Nitinols.

Topics: Adsorption; Albumins; Alloys; Animals; Cell Adhesion; Cell Line; Cell Proliferation; Coated Materials, Biocompatible; Endothelial Cells; Fibrinogen; Humans; Iron; Leukocytes, Mononuclear; Materials Testing; Neutrophils; Polysaccharides; Surface Properties; Sus scrofa; Thrombosis

This study assessed the feasibility and efficacy of implanting a new nitinol device in the left atrial appendage (LAA) in a canine model.. Left atrial thrombus occurs in the LAA in 90% of humans with nonvalvular atrial fibrillation (AF).. The Amplatzer Left Atrial Appendage Occluder Device now known as the Amplatzer Cardiac Plug (Amplatzer Medical LLC, Plymouth MN) is a new transcatheter Nitinol device containing polyester fabric designed to seal the LAA. The device was implanted in 10 canines with immediate, approximately 30 and approximately 90-day follow-up by echocardiography, angiography, and final pathological examination.. The device was successfully implanted in all animals and found to be retrievable and repositionable. There was complete occlusion of the LAA in all cases without embolization. There was no thrombus formation on the device and no pericardial effusion or impingement on the circumflex coronary artery, mitral valve, or left pulmonary vein. A single instance of tiny left atrial mural thrombus at device end screw contact was attributed to the small canine left atrium.. The success of this animal study confirms safety and feasibility of the Amplatzer Cardiac Plug. Human trials are warranted.

Topics: Alloys; Animals; Atrial Appendage; Cardiac Catheterization; Dogs; Feasibility Studies; Materials Testing; Polyesters; Prosthesis Design; Radiography; Septal Occluder Device; Thrombosis; Time Factors; Ultrasonography

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

The monoclonal antibody (mAb) to the platelet glycoprotein (GP) IIb/IIIa receptor has potent antiplatelet and antithrombotic characteristics shown to reduce thrombus-related major complications after coronary angioplasty. This mAb can be incorporated in drug-eluting stents capable of releasing single or multiple bioactive agents into the bloodstream and surrounding tissues. Stents eluting the monoclonal mouse anti-human platelet glycoprotein IIb/IIIa antibody SZ-262 were tested for their effectiveness in improving the blood compatibility and the antithrombotic characteristics by immunofluorescence and scanning electron microscopy (SEM). The SEM results convincingly demonstrated that the surface of the mAb eluting-stents was completely free of platelet uptake without any sign of cellular debris or proteinaceous deposits, compared with controls. The deformation index of platelets on the L-polylactic acid (L-PLA) coated stents were higher than bare Nitinol intravascular stents, as shown by SEM images. Monoclonal antibody to the platelet GP IIb/IIIa receptor, when eluting from L-PLA polymer-coated stents, effectively inhibits platelet aggregation in the stent microenvironment, thus demonstrating a potential capacity of reducing thrombosis, improving blood flow and arterial patency rates, and inhibiting cyclic blood flow variations. These results highlight the possibility of such monoclonal antibody-eluting stents to reduce or possibly eliminate thrombosis and in-stent restenosis.

Topics: Alloys; Animals; Antibodies, Monoclonal; Blood Platelets; Drug-Eluting Stents; Graft Occlusion, Vascular; Humans; Lactic Acid; Materials Testing; Mice; Platelet Glycoprotein GPIIb-IIIa Complex; Polyesters; Polymers; Thrombosis

The material and the surface patterns of intravascular stents play a pivotal role in activating platelets and triggering adherence of inflammatory cells that consecutively leads to renarrowing caused by neointimal hyperplasia. To improve these features, besides mechanical and chemical modifications, ways of masking the stent by covering have been developed. In addition, polymer-coated stents are used as vehicle for local drug delivery. But as substances used for this application are described to possess an inflammatory potential, this aspect has to be evaluated. In the present study we compared different approaches to surface alterations applied to a nitinol stent design. Besides commonly used techniques like passivation and electropolishing, we evaluated coatings with heparin, aluminium and a polyurethane polymer regarding their thrombogenic and inflammatory characteristics. By weaving thin elastomer fibres a graft was generated. The previously described Chandler loop was used to simulate arterial flow conditions ex vivo using rotating PVC tubings filled with human blood. All stents received 120 min of blood contact. To determine thrombocyte activation and inflammatory reaction, the platelet count and levels of beta-TG, TAT and PMN-elastase were assessed. Scanning electron microscopy was used to visualize the reactions. Mechanical polishing and passivation did not improve the stent surface characteristics while sandblasting, electropolishing and aluminium covering decreased activation of the coagulation cascade. In terms of thrombogenicity, the heparin coating had no beneficial effect. The lowest thrombogenic potential was found in the Polyurethane-coated stent group. All stents showed similar levels of polymorph nuclear granulocyte elastase except for the membrane design. While mechanical and chemical modifications are able to reduce thrombogenicity, coating with this particular polyurethane polymer seems to be superior to these approaches regarding the parameters assessed in this experimental setting. The Chandler loop is a valuable tool to test polymeric coatings ex vivo since these modifications may reduce drug performance by inducing inflammatory reaction themselves.

Topics: Alloys; Anticoagulants; Blood Vessel Prosthesis; Cells, Cultured; Coated Materials, Biocompatible; Equipment Failure Analysis; Heparin; Humans; Materials Testing; Platelet Activation; Stents; Surface Properties; Thrombosis

Topics: Alloys; Angioplasty, Balloon; Arterial Occlusive Diseases; Blood Vessel Prosthesis Implantation; Femoral Artery; Humans; Polytetrafluoroethylene; Popliteal Artery; Prosthesis Design; Stents; Thrombosis; Treatment Outcome; Vascular Patency

To establish a reproducible laboratory test to evaluate prospective vascular biomaterials with respect to their thromboinflammatory properties by examining fibrinogen, platelet, and monocyte binding. Endothelial migration onto these surfaces was used as an index of vascular healing.. To evaluate biomaterials for potential thrombogenicity and inflammation, binding assays of radiolabeled human fibrinogen, platelets, and monocytes were performed on standard pieces of vascular biomaterials, including metals and polymeric and ceramic-coated materials. Using an established in vitro endothelial cell migration model, the relative migration rate of cultured human aortic endothelial cells onto these vascular biomaterials was measured and compared. The fibrinogen, platelet, and monocyte binding results were combined along with the migration results to create an overall score of biocompatibility.. A significant direct relation of platelet and monocyte binding to the amount of adsorbed fibrinogen was observed. In contrast, migration rates of cultured human aortic endothelial cells onto the same biomaterial surfaces were found to be inversely related the amount of bound fibrinogen. Among the materials tested, stainless steel received the highest score of biocompatibility, while turbostratic carbon scored the lowest.. Fibrinogen, platelet, and monocyte binding levels, as well as endothelial migration rates onto vascular material surfaces, provide a basis for evaluating thrombogenicity, inflammatory potential, and endothelialization in the laboratory prior to in vivo testing.

Topics: Alloys; Aorta; Binding, Competitive; Biocompatible Materials; Blood Platelets; Cell Adhesion; Cell Movement; Chromium Alloys; Cobalt; Endothelial Cells; Endothelium, Vascular; Fibrinogen; Humans; Materials Testing; Monocytes; Polyhydroxyethyl Methacrylate; Polytetrafluoroethylene; Polyurethanes; Reproducibility of Results; Thrombosis

Distal embolization of plaque particulate liberated during stenting may cause periprocedural complications. The number, size, and volume of debris released during stenting, however, have not been quantified, rendering embolic protection approaches empiric. We used a novel method of microparticle size assessment to measure volume and characterize individual sizes of particles captured by the PercuSurge GuardWire balloon or a vascular filter during saphenous vein graft stenting.. Braided nitinol filters (average distal pore size 100 microns) were used in 47 saphenous vein grafts in 44 patients. The PercuSurge GuardWire was used in 17 saphenous vein grafts in 16 patients. Particulate debris was subjected to microparticle size analysis (RapidVue, Beckman Coulter). All samples contained particulate debris. For both filter and GuardWire populations, most particles were <100 microm in longest dimension (87% and 90% of particles, respectively), and the distribution of particle sizes was identical. Total embolic load per lesion for both filters and GuardWire aspirates was also similar: median embolic load per filter was 16 mm3 (range 2 to 84 mm3). Median embolic load per GuardWire was also 16 mm3 (range 7 to 42 mm3). Histopathologic analysis demonstrated that most samples contained plaque elements and platelet-rich thrombus.. During saphenous vein graft interventions, particulate retrieved with a vascular filtering device or an occlusion balloon was similar in amount and character. This supports the notion that unless soluble mediators play an important role in adverse acute clinical events after stenting, the clinical efficacy of filtering devices may be equal to that of occlusion devices.

Topics: Alloys; Calibration; Catheterization; Coronary Artery Bypass; Coronary Artery Disease; Embolism; Equipment Design; Filtration; Foam Cells; Humans; Intraoperative Complications; Microspheres; Particle Size; Randomized Controlled Trials as Topic; Saphenous Vein; Stents; Suction; Thrombosis

To present a single institution experience of long-term results after endovascular repair of abdominal aortic aneurysms (AAA) with the Stentor and Vanguard stent-grafts.. Twenty-three patients (20 men, 3 women; mean age 68 years, range 53-81 years) were included in this prospective study. A first generation nitinol stent-graft (Stentor) was used in 12 patients and a second generation (Vanguard) in 11 patients. Follow-up was performed with magnetic resonance imaging (MRI) with contrast-enhanced MR angiography (CE MRA) at 1, 6, and 12 months, and thereafter annually (median follow-up 3 years; range 8 months to 8 years). A conventional radiograph of the abdomen was also performed. Before secondary intervention the findings on MRI with CE MRA were confirmed with spiral computed tomography (CT) and/or angiography (DSA).. Only one patient (4%) had no complication. Endoleak was found in 15 patients (65%), graft migration in 8 (35%), and graft deformation in 18 (78%). Secondary endovascular repair was required in 7 patients (30%) and 7 (30%) were converted to open repair.. Complications with the Stentor and Vanguard stent-grafts were common. Long-term follow-up of endovascularly repaired AAA is mandatory.

Topics: Aged; Aged, 80 and over; Alloys; Aorta, Abdominal; Aortic Aneurysm, Abdominal; Female; Follow-Up Studies; Foreign-Body Migration; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Angiography; Magnetic Resonance Imaging; Male; Middle Aged; Prospective Studies; Radiography, Abdominal; Stents; Thrombosis; Tomography, Spiral Computed; Treatment Outcome

The aim of this study was to evaluate the thrombogenicity of different peripheral stent types in a standardized in vitro model with fresh human whole blood.. Different stents (N = 77; n = 7 of each of 11 types) were implanted in polyvinyl chloride tubing loops and filled with donor blood samples. After 120 minutes of blood circulation, the thrombin-antithrombin III complex (TAT) levels, beta-thromboglobulin (beta-TG) levels, and platelet counts were assessed.. After 2 hours, significant differences were seen. TAT values (+/- SD) with the investigated stents were 31 micro g/mL +/- 20 (control, no stent), 328 micro g/mL +/- 206 (Saxx stent, peripheral medium CrNi31 L), 651 micro g/mL +/- 760 (Palmaz Corinthian Stent, 316 L stainless steel, electropolished), 1,609 micro g/mL +/- 1,264 (Palmaz Corinthian Stent, 316 L stainless steel, not electropolished), 810 micro g/mL +/- 578 (Palmaz Schatz long medium stent), 569 micro g/mL +/- 347 (Smart Nitinol stent), 1,037 micro g/mL +/- 577 (Megalink peripheral stent), 543 micro g/mL +/- 487 (peripheral stent, electropolished), 1,674 micro g/mL +/- 2,057 (peripheral stent, not electropolished), 3,128 micro g/mL +/- 1,812 (SelfX Nitinol stent, polished), 5,897 micro g/mL +/- 2,380 (SelfX Nitinol stent, unpolished), and 1,458 micro g/mL +/- 887 (bridge stent). The platelet count (x1,000/ micro L +/- SD) was 218 +/- 35 (control, no stent), 188 +/- 22 (Saxx stent), 187 +/- 20 (Palmaz Corinthian stent, electropolished), 135 +/- 37 (Palmaz Corinthian stent, not electropolished), 170 +/- 24 (Palmaz Schatz stent), 180 +/- 36 (Smart Nitinol stent), 159 +/- 26 (Megalink peripheral stent), 173 +/- 17 (peripheral stent, electropolished), 133 +/- 51 (peripheral stent, not electropolished), 123 +/- 37 (SelfX Nitinol stent, polished), 52 +/- 27 (SelfX Nitinol stent, unpolished), and 130 +/- 31 (bridge stent).. This standardized study showed a wide range of platelet activation after stent implantation. Electropolishing clearly reduced the thrombogenicity of the stents.

Topics: Adult; Alloys; Antithrombin III; beta-Thromboglobulin; Humans; In Vitro Techniques; Microscopy, Electron, Scanning; Peptide Hydrolases; Platelet Activation; Platelet Count; Stainless Steel; Stents; Surface Properties; Thrombosis

To evaluate preliminary clinical experience in humans with the Recovery nitinol filter (RNF) for the inferior vena cava, especially the efficacy of the device and safety of its retrieval.. Thirty-two patients were followed up to assess for filter efficacy and for ability to remove the filter.. Sixteen men and 16 women aged 18-83 years (mean, 53 years) underwent treatment with the RNF. Indications for placement were recent pulmonary embolism (n = 16), recent deep venous thrombosis (n = 20), and/or prophylaxis (n = 2). Four patients had contraindications to anticoagulant therapy, and four had complications from anticoagulant therapy. The filter was successfully placed in 32 patients. In 24 (100%) of 24 patients, the filter was successfully retrieved with a jugular approach. The mean implantation period was 53 days (range, 5-134 days). Trapped thrombus was seen within the filter in seven cases. In one patient with a large trapped thrombus, the filter was noted to have migrated 4 cm cephalad. There were no episodes of pulmonary embolism or insertion-site thrombosis.. This preliminary experience in humans confirms the efficacy of the RNF. It also demonstrates the feasibility and safety of retrieval up to 134 days after implantation.

Topics: Alloys; Device Removal; Feasibility Studies; Female; Femoral Vein; Humans; Male; Middle Aged; Pulmonary Embolism; Thrombosis; Time Factors; Tomography, X-Ray Computed; Vena Cava Filters; Vena Cava, Inferior

Atherosclerotic ailments play a major role in industrial societies. Atherosclerotic disease causes stenotic narrowing of the arterial vessel system. These narrow passages can be widened with balloon angioplasty and stents are introduced to keep the passage open. In this study, stents designed for the aorto-iliac bifurcation are considered. Most of these stents used in peripheral arteries are self-expanding stents made from Nitinol, a thermo-reactive alloy. The insertion is done under radiographic control. However, the delicate metallic structure of the stent usually casts only a weak radiographic shadow and thus is difficult to detect. A stent with an innovative radio opaque tantalum marker (Luminexx, C.R. BARD--Angiomed, Karlsruhe), overcomes this problem. However, the markers extend into the blood flow and the question arises whether the markers may cause the generation of thrombi. In a model study in an enlarged model of the aorto-iliac bifurcation with an inserted stent the flow was visualized. The enlarged scale permits the observation and video recording of the flow in great detail. The Reynolds similarity is kept. A subsequent analysis of the flow in the vicinity of the markers shows a short residence time. These results indicate that the additional markers do not increase the risk of thrombus generation.

Topics: Alloys; Aorta; Arteriosclerosis; Blood Flow Velocity; Hemorheology; Humans; Iliac Artery; Image Processing, Computer-Assisted; Models, Biological; Models, Cardiovascular; Stents; Thrombosis

Acute and subacute stents thrombosis along with thrombus mediating neointimal proliferation within the stent struts remain major concerns in coronary stenting. Up to date, there is an obvious lack of data on the thrombogenicity of stent materials in physiological conditions. This study was performed to compare the relative thrombogenicity of nitinol versus stainless steel stents. Nitinol stents were laser cut to reproduce the exact geometry of the stainless steel Palmaz stents and tested in an ex vivo AV shunt porcine model under controlled conditions. Nitinol stents presented only small amounts of white and/or red thrombus principally located at the strut intersections while Palmaz stents clearly exhibited more thrombus. As a result, 125I-fibrin(ogen) adsorption and (111)I-platelets adhesion were significantly lower on nitinol than on stainless steel devices (36%, p = 0.03 for fibrin(ogen) and 63%, p = 0.01 for platelet). These results were confirmed by scanning electron observations showing different thrombus morphologies for nitinol and stainless steel. Along with the unique mechanical properties of nitinol, its promising haemocompatibility demonstrated in our study may promote their increasing use for both peripheral and coronary revascularization procedures.

Topics: Alloys; Animals; Biocompatible Materials; Blood Vessel Prosthesis; Blood Vessel Prosthesis Implantation; Fibrinogen; Humans; Microscopy, Atomic Force; Microscopy, Electron, Scanning; Platelet Adhesiveness; Stainless Steel; Stents; Surface Properties; Swine; Thrombosis

To develop a novel endovascular thrombosis model in the porcine iliac artery for the evaluation of thrombolysis and angioplasty.. A stent-inversion-graft (SIG) model combining either a 3-mm or 5-mm tapered expandable polytetrafluoroethylene (ePTFE) graft attached within a self-expandable, 10-mm nitinol stent was placed in the left common iliac artery via an ipsilateral common femoral artery approach in 24 pigs. When the iliac artery was thrombosed, urokinase (250,000 IU) plus heparin (1,000 units) were pulse sprayed via a contralateral femoral approach (n = 12). Saline pulse-spray was used as a control group (n = 12). Balloon angioplasty was performed to eliminate the stenotic tapered graft within the stent after successful thrombolysis. The efficacy of the thrombolysis was assessed with use of intravascular ultrasound (IVUS) and arteriogram.. Both the 3-mm tapered and 5-mm tapered SIG models caused iliac artery occlusion in 22 +/- 5 and 41 +/- 9 minutes, respectively, after the deployment. Luminal patency was re-established successfully in all occluded arteries after urokinase infusion. Angioplasty was successful in eliminating the tapered stenosis and restoring the normal diameter in all iliac arteries treated with urokinase. Complete thrombolysis was achieved in both models treated with urokinase.. This novel endovascular approach of inducing arterial thrombosis is simple to perform and reliably produces arterial thrombosis. The intraluminal stenosis is also amenable to angioplasty. This model is useful for the evaluation of antithrombotic treatment modality and adjunctive endovascular interventions.

Topics: Alloys; Angiography; Angioplasty, Balloon; Animals; Anticoagulants; Biocompatible Materials; Blood Vessel Prosthesis; Disease Models, Animal; Graft Occlusion, Vascular; Heparin; Iliac Artery; Injections, Intra-Arterial; Plasminogen Activators; Polytetrafluoroethylene; Prosthesis Failure; Swine; Thrombolytic Therapy; Thrombosis; Ultrasonography, Interventional; Urokinase-Type Plasminogen Activator

To assess whether the use of a prosthesis covered by a Dacron sheath might prevent pseudointimal hyperplasia in a transjugular intrahepatic portosystemic shunt (TIPS).. A TIPS procedure was performed in nine pigs, after creation of a portal vein microembolization model of portal hypertension, by using a Dacron-covered nitinol stent. The first centimeter on the lower extremity of this specially made prototype was uncovered, to avoid portal vein thrombosis. Three weeks later, the seven surviving animals underwent transjugular hemodynamic and angiographic follow-up and were then killed for gross and histologic evaluation.. Shunt insertion was possible in all pigs; two died of complications of the procedure. After 3 weeks only two shunts were patent, although a 50%-60% narrowing of the initial portion of the shunt was present; the remaining shunts were occluded. Histologic examination showed pseudointimal hyperplasia associated, in the cases of occlusion, with a luminal thrombosis.. This Dacron-covered stent did not prevent pseudointima formation over the stent and resulted in a high early occlusion rate, probably related to a pronounced tissue fibrotic response likely due to Dacron-induced inflammation.

Topics: Alloys; Angiography; Animals; Disease Models, Animal; Embolism; Equipment Design; Fibrosis; Follow-Up Studies; Graft Occlusion, Vascular; Hemodynamics; Hepatic Artery; Hyperplasia; Hypertension, Portal; Polyethylene Terephthalates; Portal Vein; Portasystemic Shunt, Transjugular Intrahepatic; Stents; Surface Properties; Survival Rate; Swine; Thrombosis; Tunica Intima; Vascular Patency

Metallic stents in small vessels go along with a significant risk of restenosis and reocclusion. Different models of stents and covering materials have been purported to prevent intraluminal neointimal proliferation by cover-based closure of the spaces in the wire mesh.. Tantalum stents covered with polyethylacrylate/polymethylmethacrylate (PEM) were implanted in the infrarenal aorta of six New Zealand white rabbits by aortotomy and compared with eight rabbits treated with uncovered tantalum stents. For deployment, covered and uncovered stents necessitated a 7-French (F) and 5-F sheath, respectively. In addition, nine human patients with arteriosclerotic lesions of the superficial femoral arteries (stenosis > 5 cm or total occlusion) were treated percutaneously with a Dacron-covered nitinol vascular stent via a 9-F sheath. Patients were followed for a mean of 13.5 months, and control angiography was performed after 6 months.. Experimental placement of the tantalum Wiktor stent was feasible technically in all cases. Five of six stents covered with PEM were occluded 3 days after placement despite the intravenous use of heparin and aspirin. In the group with uncovered stents, no area of stenosis greater than 10% was observed. There was a neointimal layer of 89 +/- 68 microns around the stent wires. Stent placement was successful in all patients. In four patients, a hyperergic reaction occurred, resulting in noninfectious periarteriitis. This complication was treated successfully with nonsteroidal antiinflammatory drugs. The primary patency was 50%, and the secondary patency (after application of a second covered stent in two patients) was 63%.. The uncovered stent induces little neointimal proliferation around the stent wires. The insertion of stents covered with PEM into the rabbit aorta was accompanied by a strong thrombotic reaction, despite sufficient anticoagulation. Dacron-covered nitinol stents showed a surprisingly high restenosis rate after 9 months of follow-up. Further research concerning the in vivo properties of new covering materials is mandatory before routine vascular clinical application.

Topics: Aged; Alloys; Animals; Aorta, Abdominal; Aortic Diseases; Arteriosclerosis; Biocompatible Materials; Constriction, Pathologic; Equipment Design; Female; Femoral Artery; Humans; Iliac Artery; Male; Polyethylene Terephthalates; Polymethacrylic Acids; Rabbits; Recurrence; Stents; Tantalum; Thrombosis

In this prospective blinded study of inferior vena caval (IVC) patency, 18 patients underwent 25 duplex ultrasound (US) and magnetic resonance (MR) angiography examinations over an eight-month period following Simon nitinol filter placement. Clinical examination for lower extremity venous stasis and plain abdominal radiography were also performed. Twenty-three of 24 MR examinations and 11 of 24 US examinations were judged technically adequate by the blinded observers. One technically adequate US exam was false positive for intraluminal caval thrombus. Thirteen technically inadequate US examinations missed 3 complete caval occlusions and 2 partial occlusions. MR identified all patients with complete or partial caval occlusion. The authors conclude that duplex US reliably confirms IVC patency only when strict criteria for technical adequacy and interpretation are met (good visualization of filter and IVC above and below filter). MR, although expensive, more reliably identifies nonoccluding intraluminal thrombus and caval occlusion. It should be the noninvasive study of choice in symptomatic patients with venous stasis and patients with recurrent pulmonary emboli.

Topics: Adult; Aged; Aged, 80 and over; Alloys; Evaluation Studies as Topic; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Prospective Studies; Thrombosis; Ultrasonography; Vascular Patency; Vena Cava Filters; Vena Cava, Inferior

Simon nitinol vena caval filters were placed percutaneously in 20 patients. Follow-up (average, 14 months) data were available for 16 patients, and four patients were lost to follow-up. There were no proved or suspected cases of pulmonary embolism after filter insertion. Complications encountered included caval penetration (n = 5, one acute and four at follow-up), caval thrombus (n = 4, two determined radiologically and two clinically), postplacement deep venous thrombosis (n = 2, one radiologic and one clinical), filter migration (n = 1), and delayed fracture of a filter leg (n = 2). Although no deaths or significant morbidity resulted from any complication, the relatively high complication rate, especially of significant caval penetration (documented in 25% of filter insertions), merits continued short- and long-term assessment of patient status after filter placement.

Topics: Adult; Aged; Aged, 80 and over; Alloys; Female; Foreign-Body Migration; Humans; Male; Middle Aged; Pulmonary Embolism; Radiography; Thrombosis; Vena Cava Filters; Vena Cava, Inferior

To determine the biocompatibility and thrombogenicity of nitinol blood clot filters, we inserted 27 nitinol wire devices into the venae cavae of 16 dogs and one sheep and studied the results angiographically and at autopsy after periods of one week to four years. Filter shape, location in the vena cava, wire cleaning procedure and wire surface finish were varied. All 18 cleaned nitinol wire filters remained patent by venogram, although some showed small venographic filling defects caused by adherent organized thrombi. Filters in larger veins tended to have less thrombus. Surface polishing and filter shape had no observable effect on thrombogenicity. Histologic study revealed patchy chronic inflammation at the surface of uncleaned filters but only benign fibrous tissue reaction for the cleaned filters. Neointimal tissue overgrowth was observed where nitinol wire contacted the wall of the vena cava. Two filters implanted for four years had no appreciable weight loss caused by corrosion. Platelet adhesion and plasma coagulation effects of nitinol wire were tested in vitro in human blood and found to be similar to those of stainless steel, which is used in comparable devices. These encouraging results suggest that nitinol may be a promising material for human intravascular prosthetic applications.

Topics: Alloys; Animals; Biocompatible Materials; Dogs; Filtration; Foreign-Body Reaction; Pulmonary Embolism; Sheep; Thrombosis; Venae Cavae