nitinol and Disease-Models--Animal

Topics: Alloys; Animals; Aorta, Thoracic; Aortic Aneurysm, Thoracic; Aortic Dissection; Blood Vessel Prosthesis; Blood Vessel Prosthesis Implantation; Disease Models, Animal; Dogs; Humans; Postoperative Complications; Prosthesis Design; Self Expandable Metallic Stents; Time Factors; Tomography, X-Ray Computed; Treatment Outcome

Our goal was to assess the viability of an alternative anchoring design for a transcatheter aortic valve based on a form-fitting principle with a self-expanding nitinol frame to reduce issues related to excess radial force.. A 26-mm outer diameter prototype of a self-expanding nitinol frame was developed to reduce the amount of necessary radial force by utilizing additional anchoring via protruding arms in each aortic sinus, thus allowing for a form-fitting principle as well as the coaxial self-alignment of the valve inside the native anatomy. The prototype valve was implanted via a transapical approach in the orthotopic position in 2 sheep. Follow-up examinations were performed at regular intervals during a 3-month period to confirm adequate function and anchoring.. Observation demonstrated secure, facilitated positioning with perfect alignment of the stent in the aortic sinuses. Repeated transthoracic echocardiography showed adequate valve function over the entire period with no change in the valve position, gradients or regurgitation. The animals remained in sinus rhythm during the entire period.. The prototype frame with its form-fitting properties has the potential to resolve issues related to malpositioning and excess radial force for transcatheter aortic valves as well as to extend the treatment possibilities to pure aortic insufficiencies. The stent is presently being tested in vitro for its long-term durability.

Topics: Alloys; Animals; Aortic Valve; Aortic Valve Insufficiency; Chronic Disease; Disease Models, Animal; Echocardiography; Feasibility Studies; Heart Valve Prosthesis; Prosthesis Design; Sheep; Stents; Transcatheter Aortic Valve Replacement

The treatment of difficult common bile duct stones (CBDS) remains a big challenge around the world. Biliary stenting is a widely accepted rescue method in patients with failed stone extraction under endoscopic retrograde cholangiopancreatography. Fully covered self-expanding metal stent (FCSEMS) has gained increasing attention in the management of difficult CBDS.. To manufacture a drug-eluting FCSEMS, which can achieve controlled release of stone-dissolving agents and speed up the dissolution of CBDS.. Customized covered nitinol stents were adopted. Sodium cholate (SC) and disodium ethylene diamine tetraacetic acid (EDTA disodium, EDTA for short) were used as stone-dissolving agents. Three different types of drug-eluting stents were manufactured by dip coating (Stent I), coaxial electrospinning (Stent II), and dip coating combined with electrospinning (Stent III), respectively. The drug-release behavior and stone-dissolving efficacy of these stents were evaluated. Stent I and Stent II had obvious burst release of drugs in the first 5 d while Stent III presented controlled and sustainable drug release for 30 d. In still buffer, the final stone mass-loss rate of each group was 5.19% ± 0.69% for naked FCSEMS, 20.37% ± 2.13% for Stent I, 24.57% ± 1.45% for Stent II, and 33.72% ± 0.67% for Stent III. In flowing bile, the final stone mass-loss rate of each group was 5.87% ± 0.25% for naked FCSEMS, 6.36% ± 0.48% for Stent I, 6.38% ± 0.37% for Stent II, and 8.15% ± 0.27% for Stent III. Stent III caused the most stone mass-loss no matter in still buffer or in flowing bile, which was significantly higher than those of other groups (. The novel SC and EDTA-eluting FCSEMS is efficient in diminishing CBDS

Topics: Alloys; Animals; Common Bile Duct; Disease Models, Animal; Drug Carriers; Drug Liberation; Drug-Eluting Stents; Edetic Acid; Gallstones; Humans; Male; Nanofibers; Polyesters; Self Expandable Metallic Stents; Sodium Cholate; Swine; Swine, Miniature; Treatment Outcome

This study was conducted to determine whether a nitinol stent coated with doxycycline prevents tracheal inflammation and fibrosis in a rabbit.. A nitinol stent coated with doxycycline was designed by us. Twelve rabbits were divided into three groups: normal, control (nondoxycycline-coated stent), and doxycycline-coated stent group. The stents were inserted into the tracheal lumen through the oral cavity. Tracheal granulation was evaluated and graded by laryngoscopy. Histological examinations evaluated the inflammatory response and fibrosis. Real-time polymerase chain reaction (PCR) and Western blot assessed the changes to the extracellular matrix (ECM).. Endoscopic findings showed that the nitinol stent coated with doxycycline resulted in lesser granulation tissue in the trachea than the noncoated stent. Histologic examination further revealed that the doxycycline-coated stent was associated with decreased inflammatory cells and reduced fibrosis, compared to the noncoated stent. In PCR and Western blot, the doxycycline-coated stent showed lower expression of ECM components inducing fibrosis.. A nitinol stent coated with doxycycline showed favorable effects in reducing tracheal inflammation and fibrosis in a rabbit model. Further research is required to study the beneficial effects of local application of doxycycline for prevention of tracheal stenosis.. NA. Laryngoscope, 128:1558-1563, 2018.

Topics: Adjuvants, Immunologic; Alloys; Animals; Anti-Bacterial Agents; Disease Models, Animal; Doxycycline; Fibrosis; Inflammation; Laryngoscopy; Rabbits; RNA, Messenger; Stents; Trachea; Tracheal Stenosis; Transforming Growth Factor beta1; Wound Healing

Mechanical right ventricular (RV) support offers a treatment option for critically ill patients with RV failure (RVF). We developed an assist device for rapid percutaneous implantation. The aim of the present study was to investigate the implantation procedure, haemodynamic performance and possible side effects of the novel right ventricular assist device - PERKAT RV - in an animal model.. The PERkutane KATheterpumptechnologie RV (PERKAT RV) device consists of a nitinol chamber covered by foil containing inflow valves. An outlet tube is attached to its distal part. The system is designed for 18 Fr percutaneous implantation. The chamber is unfolded in the inferior vena cava while the outlet tube bypasses the right heart with the tip in the pulmonary trunk. An IABP balloon is placed inside. Balloon deflation generates blood flow into the chamber; during inflation, blood is guided into the pulmonary arteries. Acute RVF was induced by venous injection of Sephadex in seven sheep for evaluation of the device. The PERKAT RV was able to improve haemodynamics immediately generating a median increase in cardiac output of 59%. Longer pump support was evaluated in a second study. Four sheep were supported for eight hours without any problems.. The percutaneous implantation and explantation of the PERKAT RV device was possible in the designed way. The sheep studies proved beneficial haemodynamic effects in acute RVF. The system offers easy and safe treatment in acute RVF.

Topics: Alloys; Animals; Device Removal; Disease Models, Animal; Female; Heart Failure; Heart-Assist Devices; Hemodynamics; Intra-Aortic Balloon Pumping; Prosthesis Design; Prosthesis Implantation; Pulmonary Embolism; Sheep, Domestic; Stents; Time Factors; Ventricular Function, Right

In this study, results of a functional in vitro study of 2 newly developed valved stents for transcatheter mitral valve implantation are presented.. Two novel stent designs, an oval-shaped and a D-shaped stent with a strut fixation system were developed. The fixation force of the novel stents were tested in vitro in porcine hearts with a tensile test set-up. In further experiments, the stents were equipped with a circular valved stent, and the valve performances were investigated in a pulsatile heart valve tester.. Sufficient mean stent fixation forces in the range of 24.2 ± 0.9 N to 28.6 ± 1.9 N were measured for the different stent models. The novel valved stents showed good performance in an in vitro pulsatile heart valve tester. A sufficient opening area and low opening pressures were measured for all tested mitral valved stents. Compared with an established reference valve, the D-shaped stent and the oval-shaped valved stent showed a lower systolic transvalvular pressure gradient, which indicates slightly greater extent of valvular leakage of the closed valved stents. However, the mitral nitinol valved stents demonstrated adequate durability.. This study indicates a sufficient annular fixation force of the tested transcatheter mitral valve implantation valved stent prototypes. Therefore, these mitral valved stents demonstrate a new type of mitral valved stent design.

Topics: Alloys; Animals; Cardiac Catheterization; Disease Models, Animal; Echocardiography; Heart Valve Prosthesis Implantation; Mitral Valve; Mitral Valve Insufficiency; Prosthesis Design; Self Expandable Metallic Stents; Swine

We assessed the transventricular placement of porcine small intestinal submucosa (SIS) stent valves in a juvenile sheep model at the 3-month follow-up evaluation.. We constructed a pulmonary stent valve by suturing a porcine SIS bicuspid valve into a bell-shaped 'Z' nitinol stent and implanted 7 SIS stent valves transventricularly in the pulmonary position in 7 sheep. The function of the stent valves was assessed using a pulsatile flow simulation system in vitro. Haemodynamic, angiographic, echocardiographic, histologic and radiographic examinations were carried out before, immediately after implantation and 3 months after implantation.. All SIS stent valves were successfully implanted in the pulmonary position in 7 sheep. Angiographic, echocardiographic, haemodyamic and macroscopic studies confirmed firm anchoring and good positioning of the stents immediately after implantation and at 3-month follow-up. All stent valves had good function immediately after implantation and at the end of the protocol, with the exception of 1 stent valve with mild stenosis detected at the end of the protocol. All SIS valves were free of calcifications and thrombus formation, and all stents were intact with no fractures and migration based on postmortem examination and X-radiography.. We demonstrated successful implantation of porcine SIS stent valves in the pulmonary position in sheep with excellent valve function at the 3-month follow-up evaluation. Porcine SIS has potential superiority as a pulmonary stent bioprosthetic valve material, and the bell-shaped nitinol stent has potential superiority as a frame for pulmonary stent valves.

Topics: Alloys; Angiography; Animals; Bioprosthesis; Disease Models, Animal; Echocardiography; Heart Valve Diseases; Heart Valve Prosthesis; Heart Valve Prosthesis Implantation; Heart Ventricles; Hemodynamics; Intestinal Mucosa; Prosthesis Design; Pulmonary Valve; Sheep; Stents; Swine

Pulmonary vein isolation (PVI) is a well-established method for the treatment of symptomatic paroxysmal atrial fibrillation, but is only partly successful with a high rate of electrical reconnection. We introduce a novel technique in which PVI is accomplished by noninvasive heating of a dedicated thermoresponse implant inserted into the pulmonary veins (PV), demonstrated in a porcine model.. A self-expanding nitinol-based implant was positioned in the common inferior PV of 11 pigs, using a fluoroscopy-guided transatrial appendage approach. Ablation was performed through contactless energy transfer from a primary extracorporal coil to a secondary heat ring (HR) embedded in the proximal part of the implant. Electrophysiological conduction was assessed prior to and postablation, and at 3 months. Histological samples were obtained acutely (n  =  4) and after 3 months (n  =  7).. In total, 13 PV implants were successfully positioned in the inferior PVs of 11 animals. Ablation was performed without injury of adjacent structures. PVI and bidirectional block was electrophysiologically confirmed in all cases immediately at the time of implantation and 3 months later in seven chronic animals in whom testing was repeated. Marked evidence of ablation around the proximal HR was evident at 3 months postprocedure, with scar tissue formation and only mild neointimal proliferation.. Successful PVI can be obtained by external electromagnetic heat transfer to a novel pulmonary vein implant.

Topics: Alloys; Animals; Atrial Fibrillation; Catheter Ablation; Disease Models, Animal; Electromagnetic Phenomena; Fluoroscopy; Prostheses and Implants; Prosthesis Design; Pulmonary Veins; Swine

The popularity of vascular stents continues to increase for a variety of applications, including coronary, lower limb, renal, carotid, and neurovascular disorders. However, their clinical effectiveness is hindered by numerous postdeployment complications, which may stimulate inflammatory and fibrotic reactions. The purpose of this study was to evaluate the vessel inflammatory response via in vivo imaging in a mouse stent implantation model. Corroded and noncorroded self-expanding miniature nitinol stents were implanted in mice abdominal aortas, and novel in vivo imaging techniques were used to assess trafficking and accumulation of fluorescent donor monocytes as well as cellular proliferation at the implantation site. Monocytes were quantitatively tracked in vivo and found to rapidly clear from circulation within hours after injection. Differences were found between the test groups with respect to the numbers of recruited monocytes and the intensity of the resulting fluorescent signal. Image analysis also revealed a subtle increase in matrix metalloproteinase activity in corroded compared with the normal stented aortas. In conclusion, this study has been successful in developing a murine stent inflammation model and applying novel in vivo imaging tools and methods to monitor the complex biological processes of the host vascular wall response.

Topics: Alloys; Animals; Aorta, Abdominal; Cell Separation; Coronary Vessels; Corrosion; Disease Models, Animal; Fluorescence; Inflammation; Male; Matrix Metalloproteinases; Metals; Mice; Monitoring, Physiologic; Monocytes; Stents

Thin film nitinol can be processed to produce a thin microporous sheet with a low percentage of metal coverage (<20%) and high pore attenuation (∼70 pores/mm(2)) for flow diversion. We present in vivo results from the treatment of experimental rabbit aneurysms by using a thin film nitinol-based flow-diversion device.. Nineteen aneurysms in the rabbit elastase aneurysm model were treated with a single thin film nitinol flow diverter. Devices were also placed over 17 lumbar arteries to model perianeurysmal branch arteries of the intracranial circulation. Angiography was performed at 2 weeks (n = 7), 1 month (n = 8), and 3 months (n = 4) immediately before sacrifice. Aneurysm occlusion was graded on a 3-point scale (grade I, complete occlusion; grade II, near-complete occlusion; grade III, incomplete occlusion). Toluidine blue staining was used for histologic evaluation. En face CD31 immunofluorescent staining was performed to quantify neck endothelialization.. Markedly reduced intra-aneurysmal flow was observed on angiography immediately after device placement in all aneurysms. Grade I or II occlusion was noted in 4 (57%) aneurysms at 2-week, in 6 (75%) aneurysms at 4-week, and in 3 (75%) aneurysms at 12-week follow-up. All 17 lumbar arteries were patent. CD31 staining showed that 75% ± 16% of the aneurysm neck region was endothelialized. Histopathology demonstrated incorporation of the thin film nitinol flow diverter into the vessel wall and no evidence of excessive neointimal hyperplasia.. In this rabbit model, the thin film nitinol flow diverter achieved high rates of aneurysm occlusion and promoted tissue in-growth and aneurysm neck healing, even early after implantation.

Topics: Alloys; Animals; Cerebral Angiography; Disease Models, Animal; Embolization, Therapeutic; Intracranial Aneurysm; Pancreatic Elastase; Rabbits; Stents

A cerebral aneurysm occurs as a result of a weakened blood vessel, which allows blood to flow into a sac or a ballooned section. Recent advancement shows that a new device, 'flow-diverter', can divert blood flow away from the aneurysm sac. People found that a flow-diverter based on thin film nitinol (TFN), works very effectively, however there are no studies proving the mechanical safety in irregular, curved blood vessels. Here, we study the mechanical behaviors and structural safety of a novel microstructured TFN membrane through the computational and experimental studies, which establish the fundamental aspects of stretching and bending mechanics of the structure. The result shows a hyper-elastic behavior of the TFN with a negligible strain change up to 180° in bending and over 500% in radial stretching, which is ideal in the use in neurovascular curved arteries. The simulation determines the optimal joint locations between the TFN and stent frame. In vitro experimental test qualitatively demonstrates the mechanical flexibility of the flow-diverter with multi-modal bending. In vivo micro X-ray and histopathology study demonstrate that the TFN can be conformally deployed in the curved blood vessel of a swine model without any significant complications or abnormalities.

Topics: Alloys; Animals; Disease Models, Animal; Endovascular Procedures; Intracranial Aneurysm; Materials Testing; Stents; Swine

Caval valve implantation has been suggested for transcatheter treatment of severe tricuspid regurgitation (TR). Combining the interventional technique with the promising surgical experience with decellularized valves, we sought to evaluate the functional and structural outcome of decellularized pericardial tissue valves (dTVs) in the low-pressure venous circulation in a chronic model of TR.. Sixteen pericardial tissue valves were heterotopically implanted in the inferior and superior vena cava in a sheep model (54-98 kg; median 74.5 kg, n = 8) of severe TR. The devices were assembled using self-expanding nitinol stents and bovine pericardia decellularized by a detergent-based protocol (group dTV; n = 8). Glutaraldehyde-fixed pericardial tissue valves served as control (GaTV, n = 8). After 6 months, device function and structural maturation were analyzed using echocardiographic, histologic, immunohistologic, and electron microscopic approaches. After implantation, cardiac output increased significantly from 3.7 ± 1.1 l/min to 4.8 ± 1.1 l/min (P < 0.05) and competent valve function was verified by angiography. At 6 months, angiographic and echocardiographic evaluation revealed moderate to severe regurgitation in all GaTV. In contrast, five of the eight dTVs functioned well with only minor regurgitation. In these animals, autopsy revealed preserved valve structure with tender leaflets without signs of thrombosis or calcification. Conversely, GaTV showed severe degeneration with large calcification areas. Microscopic and histologic analysis confirmed endothelial repopulation in both valve types. However, additional interstitial reseeding was observed in decellularized valves.. In the venous circulation in severe TR, decellularized valves show superior functional performance compared to Ga-fixed tissue valves. Macroscopic and microscopic analyses suggest preserved structural integrity and advanced endothelial and interstitial repopulation with evidence of less degradation in dTV. © 2014 Wiley Periodicals, Inc.

Topics: Alloys; Animals; Bioprosthesis; Cardiac Catheterization; Chronic Disease; Disease Models, Animal; Female; Gene Expression Regulation; Heart Valve Prosthesis; Heart Valve Prosthesis Implantation; Hemodynamics; Prosthesis Design; Recovery of Function; Severity of Illness Index; Sheep; Stents; Time Factors; Tricuspid Valve; Tricuspid Valve Insufficiency; Ultrasonography; Vena Cava, Inferior; Vena Cava, Superior

We tested the feasibility of local thrombolytic therapy via a novel hollow flexible and perforated wire in a mouse model of deep vein thrombosis. Inferior vena cava (IVC) thrombosis was induced by vessel wall exposure to ferric chloride after laparotomy in anesthetized C57Bl/6 mice. Thrombus formation was visualized by intravital microscopy of rhodamine-labeled platelets and leukocytes. A nitinol hypotube coronary wire with perforated tip was inserted via a 0.8 × 40 mm canula into the IVC lumen distal to the site of ferric chloride exposure. Either tissue plasminogen activator (tPA, alteplase) or saline (control) was administered via the platinum wire distal to the thrombus, avoiding mechanical fragmentation. Thrombus size was assessed by immunohistochemistry (platelet CD41 staining). Intravital microscopy of the IVC demonstrated platelet-containing thrombus growth starting 1 min after ferric chloride exposure. Alteplase administration resulted in significant thrombus size reduction within 10-20 min observed by intravital microscopy and confirmed by histological assessment of IVC cross-sections. Saline-treated mice (n = 4) demonstrated near total IVC occlusion with thrombotic material (84 ± 8% of cross-sectional area in serial sections), whereas alteplase-treated mice showed a dose-dependent decrease of thrombotic area [56 ± 5% with 1.5, 39 ± 4 % with 15 and 21 ± 6% with 150 mg/kg, respectively (n = 4)]. We demonstrate that a flexible hollow and perforated wire enables the successful application of thrombolytic therapy to IVC thrombi in mice without vessel wall perforation. Flexible wire-based thrombolytic therapy appears to be a safe and reliable method for thrombus dissolution even in fragile small veins and may become a promising strategy for targeted therapy of small vessel thrombosis.

Topics: Alloys; Animals; Disease Models, Animal; Fibrinolytic Agents; Male; Mechanical Thrombolysis; Mice; Thrombolytic Therapy; Tissue Plasminogen Activator; Venous Thrombosis

To evaluate the technical feasibility of a modified tapered metal tip and low profile introducer for one-step endoscopic ultrasound (EUS)-guided biliary drainage (EUS-BD) in a new experimental biliary dilatation porcine model.. A novel dedicated device for one-step EUS-guided biliary drainage system (DEUS) introducer has size 3F tapered catheter with size 4F metal tip for simple puncture of the intestinal wall and liver parenchyma without graded dilation. A self-expandable metal stent, consisting of both uncovered and nitinol-covered portions, was preloaded into DEUS introducer. After establishment of a biliary dilatation model using endoscopic hemoclips or band ligation with argon plasma coagulation in 9 mini-pigs, EUS-BD using a DEUS was performed following 19-G needle puncture without the use of fistula dilation devices.. One-step EUS-BD was technically successful in seven pigs [7/9 (77.8%) as intention to treat] without the aid of devices for fistula dilation from the high body of stomach or far distal esophagus to the intrahepatic (n = 2) or common hepatic (n = 5) duct. Primary technical failure occurred in two cases that did not show adequate biliary dilatation. In seven pigs with a successful bile duct dilatation, the technical success rate was 100% (7/7 as per protocol). Median procedure time from confirmation of the dilated bile duct to successful placement of a metallic stent was 10 min (IQR; 8.9-18.1). There were no immediate procedure-related complications.. Modified tapered metal tip and low profile introducer may be technically feasible for one-step EUS-BD in experimental porcine model.

Topics: Alloys; Animals; Bile Ducts; Dilatation; Disease Models, Animal; Drainage; Endoscopy; Female; Intestines; Liver; Metals; Models, Animal; Pilot Projects; Stents; Swine; Swine, Miniature; Treatment Outcome; Ultrasonography

To assess the fatigue and in vivo performance of a new stent-graft incorporating bovine peritoneum lining that is designed for application in peripheral vascular occlusive disease.. Bovine peritoneum-lined stent-grafts were subjected to accelerated in vitro pulsatile fatigue and axial/torsional fatigue testing designed to simulate 10 years of physiological strain on the devices. At specified times the devices were evaluated for stent fracture, suture failure, or tissue tearing. Seven dogs underwent bilateral common iliac artery (CIA) balloon angioplasty injury with unilateral placement of the peritoneum-lined stent-graft. Angiography and intravascular ultrasound were performed prior to treatment, after treatment, and prior to sacrifice at 30 days. Vessels were perfusion fixed and histologically evaluated at 5 regions: above stent, proximal stent, mid stent, distal stent, and below stent.. No evidence of stent, suture, or tissue failure was present during or after pulsatile and axial/torsional fatigue testing. At 30±0.3 days after implantation, all vessels were patent. The average lumen area at explantation across stented vessels was 25.45 mm(2). Lumen areas tended to be reduced above (23.57 mm(2)) and below (24.17 mm(2)) the stent. Lumen areas were consistent across stented regions at explantation (proximal stent 27.80 mm(2), mid stent 25.88 mm(2), and distal stent 25.81 mm(2)). The mean neointimal area in peritoneum-lined stents was 2.02±1.52 mm(2), with a neointima:media ratio of 1.03±0.50. These values were significantly lower in the above and below stent areas than in the stented regions, but there was no difference in either measure within the proximal, mid, or distal stent.. The custom-designed peritoneum-lined stent-graft is promising for clinical peripheral applications due to its ability to resist relevant long-term physiological stresses and outstanding short-term patency rates in canine implantations.

Topics: Alloys; Animals; Bioprosthesis; Blood Vessel Prosthesis; Blood Vessel Prosthesis Implantation; Cattle; Disease Models, Animal; Dogs; Endovascular Procedures; Equipment Failure Analysis; Female; Hemodynamics; Iliac Artery; Materials Testing; Peritoneum; Prosthesis Design; Prosthesis Failure; Regional Blood Flow; Stents; Stress, Mechanical; Time Factors; Torsion, Mechanical; Vascular System Injuries

The aim of this study was to evaluate a new type of occluder for patent ductus arteriosus. Patent ductus arteriosus was established in a canine model by anastomosing a length of autologous jugular vein to the descending aorta and the left pulmonary artery in an end-to-side fashion. Transcatheter closure of each patent ductus arteriosus was performed on 10 dogs, which were then monitored for as long as 6 months with aortography, echocardiography, and histologic evaluation. Transcatheter closure with use of the novel pan-nitinol device was successful in all canine models. Postoperative echocardiography showed that the location and shape of the occluders were normal, without any residual shunting. Further histologic evaluation confirmed that the occluder surface was completely endothelialized 3 months after implantation. Transcatheter patent ductus arteriosus closure with the pan-nitinol occluder can be performed safely and successfully in a canine model and shows good biological compatibility and low mortality rates.

Topics: Alloys; Anastomosis, Surgical; Animals; Aorta, Thoracic; Aortography; Cardiac Catheterization; Disease Models, Animal; Dogs; Ductus Arteriosus, Patent; Echocardiography; Equipment Design; Feasibility Studies; Jugular Veins; Materials Testing; Microscopy, Electron, Scanning; Pulmonary Artery; Septal Occluder Device; Time Factors

Despite the considerable progress made in the stent development in the last decades, cardiovascular diseases remain the main cause of death in western countries. Beside the benefits offered by the development of different drug-eluting stents, the coronary revascularization bears also the life-threatening risks of in-stent thrombosis and restenosis. Research on new therapeutic strategies is impaired by the lack of appropriate methods to study stent implantation and restenosis processes. Here, we describe a rapid and accessible procedure of stent implantation in mouse carotid artery, which offers the possibility to study in a convenient way the molecular mechanisms of vessel remodeling and the effects of different drug coatings.

Topics: Alloys; Animals; Carotid Arteries; Coronary Restenosis; Disease Models, Animal; Drug-Eluting Stents; Male; Mice; Mice, Inbred C57BL; Plaque, Atherosclerotic; Stents

This study evaluated feasibility and safety of implanting the polyester-coated nitinol ventricular septal defect occluder (pcVSDO) in the canine model.. VSD models were successfully established by transseptal ventricular septal puncture via the right jugular vein in 15 out of 18 canines. Two types of VSDOs were implanted, either with pcVSDOs (n = 8) as the new type occluder group or with the commercial ventricular septal defect occluders (VSDOs, n = 7, Shanghai Sharp Memory Alloy Co. Ltd.) as the control group. Sheath size was 10 French (10 Fr) in two groups. Then the general state of the canines was observed after implantation. ECG and TTE were performed, respectively, at 7, 30, 90 days of follow-up. The canines were sacrificed at these time points for pathological and scanning electron microscopy examination. The devices were successfully implanted in all 15 canines and were retrievable and repositionable. There was no thrombus formation on the device or occurrence of complete heart block. The pcVSDO surface implanted at day 7 was already covered with neotissue by gross examination, and it completed endothelialization at day 30, while the commercial VSDO was covered with the neotissue in 30th day and the complete endothelialization in 90th day.. The study shows that pcVSDO is feasible and safe to close canine VSD model and has good biocompatibility and shorter time of endothelialization.

Topics: Alloys; Animals; Catheters; Coated Materials, Biocompatible; Disease Models, Animal; Dogs; Heart Septal Defects, Ventricular; Humans; Polyesters; Septal Occluder Device

To evaluate the feasibility and efficacy of a new nanoplatinum-coated nitinol device for transcatheter ventricular septal defect (VSD) closure in a swine model.. In spite of its good closure results, the previous version of Amplatzer perimembranous VSD device had a relatively high incidence of complete heart block as compared to surgical closure. This new VSD device is made from meshed nitinol wires, nanoplatinum-coated and filled with polypropylene sheaths to enhance thrombogenicity. With special design, the device has minimal expanding pressure on the nearby tissue. This may reduce the possibility of atrioventricular block after implantation.. VSD was created in 12 pigs via retrograde aortic approach, by ventricular septal puncture with Brokenbrough needle and ventricular septal balloon dilation, under echocardiographic and fluoroscopic guidance. After imaging study, the device was deployed for VSD closure.. The device was successfully deployed to close the created VSD in all 12 animals. Angiographic and echocardiographic studies demonstrated complete closure of the VSD in 11 animals. One animal had residual VSD leakage. Three animals had unstable hemodynamics and died within 12 hours after the procedure. The remaining 9 animals survived in normal condition. The autopsy findings demonstrated complete endothelialization at 8 weeks after implantation.. Transcatheter VSD closure with the new nanoplatinum-coated nitinol device is feasible and efficacious. The good occlusion results and complete endothelialization after implantation in the swine model potentiates human application.

Topics: Alloys; Animals; Cardiac Catheterization; Coated Materials, Biocompatible; Disease Models, Animal; Echocardiography; Heart Septal Defects, Ventricular; Nanostructures; Platinum; Prostheses and Implants; Prosthesis Design; Septal Occluder Device; Swine; Treatment Outcome

Regenerative cell-based therapies are associated with limited myocardial retention of delivered stem cells. The objective of this study is to develop an endocardial delivery system for enhanced cell retention.. Stem cell retention was simulated in silico using 1- and 3-dimensional models of tissue distortion and compliance associated with delivery. Needle designs, predicted to be optimal, were accordingly engineered using nitinol, a nickel and titanium alloy displaying shape memory and superelasticity. Biocompatibility was tested with human mesenchymal stem cells. Experimental validation was performed with species-matched cells directly delivered into Langendorff-perfused porcine hearts or administered percutaneously into the endocardium of infarcted pigs. Cell retention was quantified by flow cytometry and real-time quantitative polymerase chain reaction methodology. Models, computing optimal distribution of distortion calibrated to favor tissue compliance, predicted that a 75°-curved needle featuring small-to-large graded side holes would ensure the highest cell retention profile. In isolated hearts, the nitinol curved needle catheter (C-Cath) design ensured 3-fold superior stem cell retention compared with a standard needle. In the setting of chronic infarction, percutaneous delivery of stem cells with C-Cath yielded a 37.7±7.1% versus 10.0±2.8% retention achieved with a traditional needle without effect on biocompatibility or safety.. Modeling-guided development of a nitinol-based curved needle delivery system with incremental side holes achieved enhanced myocardial stem cell retention.

Topics: Alloys; Animals; Cell- and Tissue-Based Therapy; Computer Simulation; Disease Models, Animal; Drug Delivery Systems; Endocardium; Equipment Design; Male; Myocardial Infarction; Needles; Stem Cell Transplantation; Stem Cells; Swine; Treatment Outcome

To compare the performance of small intestinal submucosa (SIS)-covered endografts (SCEs) to bare nitinol stents (BSs) in injured swine iliac arteries.. Twenty-eight nitinol stents were used: 14 externally SCEs and 14 BSs. Devices were implanted in each side of balloon-injured external iliac arteries of 14 swine via carotid approach. Arteriograms were obtained before and after implantation and before animal sacrifice at 4, 8, and 12 weeks. Histopathological and electron microscopy studies of explanted specimens were performed.. Implantation of all SCEs and BSs was technically successful, but one SCE and one BS were obstructed at 8 weeks after implantation. At sacrifice, the other 26 stents were patent, with angiogram showing no significant different luminal narrowing between SCEs and BSs. Proliferating cell nuclear antigen (PCNA) immunohistochemistry examination revealed that the percentage of PCNA(+) cells were lower in SCEs (p<0.05). Additionally, histomorphological analysis indicated that the neointima area and percentage of narrowing area were greater in SCEs, but there was no statistical significance. Greater endothelial cell count in SCEs than in BSs per visual field at 4000 times magnification by scanning electron microscope (p<0.05).. Compared to BSs, no definite decrease of neointima and restenosis was found in SCEs in the present study. However, it is effective in promoting endothelial regeneration and strengthening endothelial function.

Topics: Alloys; Analysis of Variance; Angiography; Angioplasty; Animals; Disease Models, Animal; Graft Occlusion, Vascular; Iliac Artery; Immunohistochemistry; Intestinal Mucosa; Intestine, Small; Microscopy, Electron, Scanning; Prosthesis Design; Stents; Swine

The aim of this study was to create an ovine arteriovenous fistula (AVF) model which would closely replicate a human forearm fistula and use this to quantify the degree of intimal hyperplasia in those created with the U-Clip compared to a conventional sutured anastomosis.. Twenty AVFs were created in 10 Border Leicester-Merino sheep between the superficial femoral artery and vein of each hind limb. On one side the U-Clip and on the other a continuous polypropylene suture was used to perform the anastomosis. The animals were sacrificed at 2 (n = 3), 4 (n = 4), 6 (n = 3) weeks and histological slices were taken of each AVF in cross section to determine the intimal media area per unit length (IMA/L).. Intimal hyperplasia (IH) was observed at all time points with one AVF found occluded with thrombus at the time of harvest. The IMA/L was significantly lower in the U-Clip groups by 24% at 2 weeks, 32% at 4 weeks and 23% at 6 weeks (Two-way ANOVA, p = 0.019, observed power = 0.825, time or side p ≥ 0.766, type p = 0.001; Paired t-test, p < 0.001 between matched anastomotic types). Time taken to perform the anastomosis was similar between the two anastomotic techniques (Polypropylene 14(8-18) vs. U-Clip 15.3(11-23) min; p = 0.47).. This ovine AVF model results in IH similar to that seen in a human AVF. The IH that occurs with the U-Clip is less than that of continuous polypropylene suture.

Topics: Alloys; Anastomosis, Surgical; Animals; Arteriovenous Fistula; Disease Models, Animal; Hyperplasia; Sheep; Surgical Instruments; Sutures; Tunica Intima

A flexible, low profile, flow diversion stent could replace endovascular coiling for the treatment of intracranial aneurysms. Micropatterned-thin film nitinol (TFN) is a novel biomaterial with high potential for use in next-generation endovascular devices. Recent advancements in micropatterning have allowed for fabrication of a hyperelastic thin film nitinol (HE-TFN). In this study, the authors describe in vitro and in vivo testing of novel HE-TFN based flow diverting stents. Two types of HE-TFN with expanded pores having long axes of 300 and 500 μm were used to fabricate devices. In vitro examination of the early thrombotic response in whole blood showed a possible mechanism for the device's function, whereby HE-TFN serves as a scaffold for blood product deposition. In vivo testing in swine demonstrated rapid occlusion of model wide-neck aneurysms. Average time to occlusion for the 300-μm device was 10.4 ± 5.5 min. (N = 5) and 68 ± 30 min for the 500-μm device (N = 5). All aneurysms treated with bare metal control stents remained patent after 240 min (N = 3). SEM of acutely harvested devices supported in vitro results, demonstrating that HE-TFN serves as a scaffold for blood product deposition, potentially enhancing its flow-diverting effect. Histopathology of devices after 42 days in vivo demonstrated a healthy neointima and endothelialization of the aneurysm neck region. HE-TFN flow-diverting stents warrant further investigation as a novel treatment for intracranial aneurysms.

Topics: Alloys; Animals; Disease Models, Animal; Female; Humans; Intracranial Aneurysm; Materials Testing; Porosity; Stents; Swine

The field of interventional cardiovascular MRI is hampered by the unavailability of active guidewires that are both safe and conspicuous. Heating of conductive guidewires is difficult to predict in vivo and disruptive to measure using external probes. We describe a clinical-grade 0.035" (0.89 mm) guidewire for MRI right and left heart catheterization at 1.5 T that has an internal probe to monitor temperature in real-time, and that has both tip and shaft visibility as well as suitable flexibility.. The design has an internal fiberoptic temperature probe, as well as a distal solenoid to enhance tip visibility on a loopless antenna. We tested different tip-solenoid configurations to balance heating and signal profiles. We tested mechanical performance in vitro and in vivo in comparison with a popular clinical nitinol guidewire.. The solenoid displaced the point of maximal heating ("hot spot") from the tip to a more proximal location where it can be measured without impairing guidewire flexion. Probe pullback allowed creation of lengthwise guidewire temperature maps that allowed rapid evaluation of design prototypes. Distal-only solenoid attachment offered the best compromise between tip visibility and heating among design candidates. When fixed at the hot spot, the internal probe consistently reflected the maximum temperature compared external probes.Real-time temperature monitoring was performed during porcine left heart catheterization. Heating was negligible using normal operating parameters (flip angle, 45°; SAR, 1.01 W/kg); the temperature increased by 4.2°C only during high RF power mode (flip angle, 90°; SAR, 3.96 W/kg) and only when the guidewire was isolated from blood cooling effects by an introducer sheath. The tip flexibility and in vivo performance of the final guidewire design were similar to a popular commercial guidewire.. We integrated a fiberoptic temperature probe inside a 0.035" MRI guidewire. Real-time monitoring helps detect deleterious heating during use, without impairing mechanical guidewire operation, and without impairing MRI visibility. We therefore need not rely on prediction to ensure safe clinical operation. Future implementations may modulate specific absorption rate (SAR) based on temperature feedback.

Topics: Alloys; Animals; Cardiac Catheterization; Cardiac Catheters; Disease Models, Animal; Equipment Design; Heart Diseases; Magnetic Resonance Imaging, Cine; Magnetic Resonance Imaging, Interventional; Optical Fibers; Pliability; Swine; Temperature

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

Secure access and reliable closure is paramount in the setting of transesophageal mediastinal endoscopic surgery. The purpose of this study was to develop a secure transesophageal access technique and to evaluate the feasibility, safety, and efficacy of a novel covered, self-expanding, retractable stent for closure of 15-mm esophageal defects.. Fifteen-millimeter esophagotomies were created in 18 domestic pigs using needle knife puncture and balloon dilatation or a blunt dissection technique. Six animals were randomly assigned to open surgical repair and six animals to endoscopic closure using a self-expanding, covered, nitinol stent (Danis SX-ELLA stent, ELLA-CS) in a nonsurvival setting. Pressurized leak tests were performed on all closures. Six animals underwent transesophageal endoscopic mediastinal interventions and survived for 17 days. Stents were extracted at day 10.. Nonsurvival experiments revealed two bleeding complications associated with the needle-knife access technique, while blunt-dissection mediastinal access was not associated with any complications. Leak test results were not different for stent compared to surgical closures. All survival animals were found to have complete closure and adequate healing of the esophagotomies. No leakage or infectious complication occurred.. Blunt dissection achieves safe access into the mediastinum. Stent closure achieves similar leak test results compared to surgical closure and results in adequate sealing and wound healing of 15-mm esophageal defects.

Topics: Alloys; Animals; Biopsy; Disease Models, Animal; Equipment Design; Esophageal Diseases; Esophagoscopy; Feasibility Studies; Mediastinum; Natural Orifice Endoscopic Surgery; Pleura; Radiography, Thoracic; Random Allocation; Stents; Surgical Instruments; Swine

To evaluate the feasibility of using covered stents vs. bare stents in a model of central vein stenosis with an arteriovenous graft created to mimic the conditions in hemodialysis patients.. In 7 mongrel dogs, an expanded polytetrafluoroethylene-covered nitinol stent was placed in one common iliac vein and a bare stent was placed in the contralateral vein. Arteriovenous grafts were created bilaterally between the common femoral artery and vein to induce endothelial damage. Neointima formation in the covered stents was compared to the bare stents at 12 weeks using microscopy and histochemical staining.. Two dogs were excluded due to thrombosis and infection of the arteriovenous grafts, but all stents in the remaining 5 dogs were patent. Smooth, complete neointimal coverage was observed on the inner surface of all the covered stents without intraluminal thrombus. In contrast, incomplete neointimal coverage was seen in all bare stents, with small focal thrombi adhering to the neointima on 3 bare stents. Focal nodular neointimal hyperplasia with denudation of the endothelium was observed in only 2 bare stents. Mean neointimal thickening was significantly greater in the covered stents. Eccentric neointimal thickening was observed at the inflow and outflow segments of both types of stents.. Covered stents are technically feasible for the treatment of central vein stenosis, and they demonstrate complete, smooth neointimal coverage in normal central veins, but they also display greater neointimal thickening than bare stents.

Topics: Alloys; Animals; Arteriovenous Anastomosis; Blood Vessel Prosthesis; Constriction, Pathologic; Disease Models, Animal; Dogs; Feasibility Studies; Femoral Artery; Iliac Vein; Neointima; Polytetrafluoroethylene; Prosthesis Design; Renal Dialysis; Stents

Prior studies demonstrated the feasibility of lengthening intestinal segments with mechanical force, but no previous studies have restored the lengthened segment back into intestinal continuity.. A 1-cm segment of isolated rat jejunum was lengthened using a Nitinol spring. After lengthening, this segment was restored into intestinal continuity via a transection of the intact small intestine. Rats were euthanized 2 weeks later to retrieve the restored intestinal segment for histologic and enzymatic analyses.. The isolated jejunal segments were initially lengthened to 3.3 ± 0.9 cm. After the lengthened segments were restored into intestinal continuity for 2 weeks, the final length of the restored segment was 1.9 ± 0.7 cm. All rats continued to gain weight, and the intestine proximal to the restored jejunal segment remained normal 2 weeks later. The restored jejunal segment had an increase in crypt depth and no difference in villus height compared with normal jejunum. Sucrase activity in the restored segment was not different from that in normal jejunum.. Mechanically lengthened jejunum can be restored into intestinal continuity and appears to have normal function. This further demonstrates the feasibility of mechanical enterogenesis as a potential therapy for short bowel syndrome.

Topics: Alloys; Anastomosis, Surgical; Animals; Capsules; Cellulose; Coated Materials, Biocompatible; Disease Models, Animal; Equipment Design; Female; Implants, Experimental; Intestinal Mucosa; Jejunum; Microvilli; Organ Size; Polyethylene; Rats; Rats, Sprague-Dawley; Short Bowel Syndrome; Stress, Mechanical; Sucrase; Tissue Expansion; Tissue Expansion Devices; Weight Gain

Transcatheter replacement or repair of mitral valve regurgitation has proved demanding. We aimed for a new approach to anchor a biologic heart valve in the mitral position by inserting a valve-carrying hollow body into the left atrium. This approach was investigated in both a simulation and an animal model.. After creating a mold representing the porcine left atrium from the pulmonary veins as far as the mitral valve, a nitinol skeleton was sutured onto interlaced yarns of polyvinylidene fluoride fitting the mold. The resulting device was equipped with a commercially available stentless valve (25 mm) and investigated in a simulator regarding basic functionality. Furthermore, the device was implanted in 8 female pigs through incision of the left atrium during extracorporeal circulation. Before implantation, artificial regurgitation was created by means of excision from the posterior mitral leaflet. Hemodynamic, echocardiographic, and radiologic examinations followed. For a postmortem examination, the entire heart and the lungs were excised.. We could demonstrate the functionality of the heart valve in a complex, collapsible, and self-expanding hollow body. The device adapted to the surrounding structures, leading to an exclusion of the left atrium. Sufficient treatment of mitral regurgitation was monitored hemodynamically and by means of echocardiographic analysis, although overall visualization remained difficult. Therefore in 4 animals computed tomographic scans were performed. Autopsy revealed proper positioning without major trauma to the surrounding structures.. Anchoring an additional heart valve in the atrioventricular position does not necessarily need to be performed in the heart valve structure itself. Placement of an additional valve in the mitral position is feasible through this approach.

Topics: Alloys; Animals; Cardiac Catheterization; Disease Models, Animal; Echocardiography, Transesophageal; Feasibility Studies; Female; Heart Valve Prosthesis; Heart Valve Prosthesis Implantation; Hemodynamics; Materials Testing; Mitral Valve; Mitral Valve Insufficiency; Models, Anatomic; Polyvinyls; Prosthesis Design; Swine; Tomography, X-Ray Computed

The Amplatzer ventricular septal defect (VSD) occluder has a fixed stainless steel pin bottom protruding out of the surface at the center of the discs on both sides. Theoretically, this protruding bottom may interfere with epithelialization or, in some cases, cause thrombosis.. To evaluate a new type of pan-nitinol VSD occluder without the protruding stainless steel pin bottom on both sides in a canine VSD model designed to ensure safety, effectiveness, and feasibility.. VSDs were successfully created by transseptal ventricular septal puncture with a Brockenbrough needle and dilation with an 8-mm-diameter balloon via the right jugular vein in 9 out of 12 canines. The new type VSD occluder was successfully implanted in 8 of the 9 modeled canines. No procedure- or device-related complication was observed. Transthoracic echocardiography and MRI 2 months after device implantations showed that there was no device dislocation or heart valve dysfunction in 6 of the 8 tested canines. In addition, gross and pathological examinations 3-6 months after implantation showed no corrosion of the devices or serious inflammatory reactions in the modeled animals. Complete endothelialization was seen over the surface of the discs.. The new pan-nitinol VSD device can be successfully implanted in a canine VSD model via a transcatheter approach featuring high success rate, low risk of procedure-related complications, and sound biocompatibility. The result suggests that this new VSD occluder could be used safely in future clinical trials for further test.

Topics: Alloys; Angioplasty, Balloon, Coronary; Animals; China; Disease Models, Animal; Dogs; Electrocardiography; Euthanasia, Animal; Heart Septal Defects, Ventricular; Prosthesis Implantation; Treatment Outcome

The aim of this study in canines was to investigate the effectiveness and safety of self-expandable metal stents, which were coated with paclitaxel to minimize the tissue response.. 14 dogs (5-10 kg) were randomly allocated to two groups. Drug-eluting stents (DES, n = 7) or nondrug-eluting stents (non-DES, n = 7) were endoscopically inserted and fixed in the esophagus of healthy dogs. Every 2 weeks, for a maximum period of 8 weeks, an endoscopic examination was performed to evaluate the status of stent insertion, the grade of tissue hyperplasia, and mucosal change at both ends of the stent.. One case of stent migration was observed after 4 weeks in the non-DES group. In this group, tissue reaction and hyperplasia remained for more than 4 weeks after stent insertion. By contrast, an endoscopic examination of the surrounding esophageal mucosa in the DES group showed very little tissue reaction, and the stent was easily separated from the esophageal tissue.. Although further studies are required to confirm our results, we suggest that these newly designed DES may provide an alternative tool to manage refractory benign esophageal stricture.

Topics: Alloys; Animals; Antineoplastic Agents, Phytogenic; Cell Division; Disease Models, Animal; Dogs; Drug-Eluting Stents; Epithelium; Equipment Design; Esophageal Stenosis; Esophagoscopy; Esophagus; Focal Adhesions; Granulation Tissue; Mucous Membrane; Paclitaxel

To compare outcomes with a thermoplastic polyurethane (TPU)-covered self-expanding nitinol stent-graft (TPU graft) with those of a bare self-expanding nitinol stent in a porcine model.. Fourteen TPU grafts and 14 commercially available bare nitinol stents were implanted, one each, in the iliac arteries of 14 minipigs. Follow-up was performed at 1 week (six animals), 4 weeks (four animals), and 12 weeks (four animals). The primary study endpoint was in-stent stenosis assessed with quantitative angiography and microscopy. Secondary endpoints were injury, inflammation, and endothelialization.. After 1 week, the maximum percentage luminal loss was significantly greater in TPU grafts (average, 16.2%; range, 0.0%-35.8%) than in bare nitinol stents (8.2%; 0.0%-17.3%) (P = .04). Three of the four TPU grafts were occluded after 4 weeks, and all four TPU grafts were occluded after 12 weeks. Binary stenosis was seen in three of four bare nitinol stents after both 4 and 12 weeks. At 4-week follow-up, the average percentage luminal loss was significantly greater in TPU grafts (85.2%; 40.8%-100%) than in bare nitinol stents (49.5%; 37.9%-62.4%) (P = .003). The difference in neointimal height and percentage average stenosis between TPU grafts (1,028.7 microm and 68.4%) and bare nitinol stents (1,033.6 microm [918.0-1,118.40 microm] and 68.1% [60.44%-71.99%]) was not statistically significant. After 12 weeks, the average percentage luminal loss was 100% in TPU grafts due to occlusion of all stent-grafts and 24.9% (8.0%-63.9%) in bare nitinol stents (P = .011).. TPU grafts failed to provide improved patency compared with the bare nitinol stents because of excessive neointimal growth and subsequent occlusion. In addition, the bare nitinol stents showed considerable in-stent stenosis at angiography and microscopy.

Topics: Alloys; Animals; Blood Vessel Prosthesis; Coated Materials, Biocompatible; Disease Models, Animal; Equipment Design; Equipment Failure Analysis; Graft Occlusion, Vascular; Hot Temperature; Humans; Iliac Artery; Plastics; Polyurethanes; Porosity; Radiography; Stents; Swine

Prostatic urethral stents are effective in relieving obstructions caused by benign prostatic hyperplasia (BPH). However, migration of these stents occurs frequently.. To evaluate the efficacy of a flared stent for decreasing the migration rate in comparison with a straight stent in a canine prostatic urethral model.. The flared stent (15 mm in diameter and 20 mm in length) was flared up to 19 mm at both ends to prevent migration. A straight stent with the same size was straight without flaring. Both stents were made of a nitinol wire filament and covered with an expanded polytetrafluoroethylene (ePTFE) membrane. The flared stent was inserted in the prostatic urethra of 10 dogs (group 1) and the straight stent in the prostatic urethra of 12 dogs (group 2). Follow-up retrograde urethrography (RUG) was performed 1, 4, and 8 weeks after stent placement. Fisher's exact test was used to compare the migration rate between the two groups. When stent migration occurred during the follow-up period, the same type of stent was inserted again.. Three of 10 (30.0%) flared stents migrated into the urinary bladder between 1 week and 4 weeks after placement. Seven of 12 (58.3%) straight stents migrated into the urinary bladder 1 (n = 3), 4 (n = 1), and 8 (n = 3) weeks following placement. The flared stent group showed lower migration rate than the straight stent group, but the migration rate did not reach statistical significance (P = 0.231). After the second stent placement, one of three (33.3%) flared stents migrated again after 4 weeks and two of seven straight stents (28.6%) after 1 week.. Although the migration rate was not statistically significant, the flaring of the stent seemed to reduce the migration rate in comparison with straight stents in a canine prostatic urethral model. However, the migration rate of the flared stent was still high, and further developments are required to decrease migration rate.

Topics: Alloys; Animals; Coated Materials, Biocompatible; Disease Models, Animal; Dogs; Equipment Design; Follow-Up Studies; Foreign-Body Migration; Male; Polytetrafluoroethylene; Prostate; Radiography; Stents; Treatment Outcome; Urethra; Urinary Bladder

To compare aortic intimal thickening of normal and hyperhomocysteinemic pigs (induced with a methionine-rich diet) following placement of a self-expanding nitinol stent.. Eighteen Macau pigs were used. They were older than eight weeks in age and had an average weight of 30 kg. Pigs were randomly divided into two groups. The first, Group C (control), was fed a regular diet, and the second group, Group M, was fed a methionine-rich diet for 30 days to induce hyperhomocysteinemia. The self-expandable nitinol stents were 25mm in length and 8 mm in diameter after expansion. Blood samples were collected to measure total cholesterol, triglycerides, HDL and homocysteine concentrations. All animals were subjected to angiography. Thirty days after the procedure, the animals were sacrificed, and the abdominal aorta was removed for histological and digital morphometry analysis.. Under microscopic evaluation, the intima was significantly thicker in Group C than in Group M. When groups were compared by digital morphometric analysis, intimal thickening of the vessel wall was higher in Group C than in Group M. There was no significant change in total cholesterol, triglycerides or HDL concentrations in either group. In group C the levels of plasma homocysteine ranged from 14,40 to 16,73 micromol/l; in Group M, plasma homocysteine levels ranged from 17.47 to 59.80 micromol/l after 30 days of a methionine-rich diet.. Compared to normal pigs, less intimal hyperplasia was observed in the abdominal aortas of hyperhomocysteinemic pigs thirty days after the insertion of a self-expandable nitinol stent.

Topics: Alloys; Animals; Aorta; Aorta, Abdominal; Atherosclerosis; Biocompatible Materials; Cholesterol, HDL; Coronary Restenosis; Diet, Atherogenic; Disease Models, Animal; Hyperhomocysteinemia; Hyperplasia; Random Allocation; Stents; Swine; Triglycerides; Tunica Intima

A prototype endovascular electromechanical clot-extraction device was fabricated using a combination of shape memory polymer and shape memory nickel-titanium alloy (nitinol). Five embolic vascular occlusions were created in 4 rabbits by injecting thermally coagulated blood through a 4F catheter in the common carotid artery. Angiography immediately after clot injection showed complete or partial occlusion of the common carotid artery. Posttreatment angiography showed complete (2/5), partial (2/5), or no (1/5) restoration of blood flow.

Topics: Acute Disease; Alloys; Animals; Cerebral Angiography; Disease Models, Animal; Embolectomy; Equipment Design; Intracranial Embolism; Polymers; Rabbits

Control of distal pulmonary artery (PA) pressure and flow is a critical step in palliating infants with complex congential heart disease. Surgical procedures to protect or isolate the pulmonary circulation carry significant risk and can be unpredictable. Interventional control of pulmonary pressure/flow with an intravascular device (band) could reduce risk and improve regulation of pulmonary flow.. Internal pulmonary bands were created from woven nitinol to create an internal orifice estimated to reduce distal pulmonary arterial pressure by 50%. Two designs were tested, a single eccentric lumen and two symmetrical lumens. The devices were approximately 7-mm long and the external diameter varied to suit the pulmonary arterial lumen size. A total of 15 devices were implanted in seven lambs with a stented ductus arteriosus to create high pulmonary pressure/flow. Four lambs were followed with devices and stent in place for a mean of 37 +/- 13 days.. Fourteen of 15 devices were successfully implanted. One was acutely removed since the size was too large. Both device designs created greater than a 50% reduction in distal pulmonary pressure. Main PA pressure was 70/38, mean 50 +/- 13 mm Hg, and distal PA pressure 25/16, mean 20 +/- 7 mm Hg (P < 0.05). Angiography demonstrated protection of the internal banded pulmonary segments from overcirculation. Late follow-up showed that the device lumen(s) remained patent. Histology showed the vessel media to be intact but there was intimal proliferation where the device approximated the wall. There were no thrombotic emboli detected.. Percutaneous internal banding of the pulmonary arteries was feasible and successful in lambs with high pulmonary flow/pressure analogous to infants with complex congenital heart disease.

Topics: Alloys; Angiography; Animals; Animals, Newborn; Blood Pressure; Cardiac Catheterization; Disease Models, Animal; Ductus Arteriosus; Equipment Design; Feasibility Studies; Heart Defects, Congenital; Hypertension, Pulmonary; Pulmonary Artery; Pulmonary Circulation; Sheep; Stents; Time Factors; Vascular Patency; Vascular Surgical Procedures

Closure of the gastrotomy when performing transgastric procedures is one of the most challenging steps to overcome. Several methods of gastric closure have been described, but a simple and safe technique is still lacking.. To evaluate the technical feasibility and safety of a new method of endoscopic gastric closure using a nitinol septal occluder in a porcine survival model.. Endoscopic animal experimental study in a porcine survival model.. In 6 male pigs under general anesthesia, a 1-cm full-thickness gastrotomy was performed on the anterior body of the stomach and closed with a nitinol septal occluder (Occlutech). Postoperative follow-up included endoscopy and laparoscopy at 1, 2, 4, and 6 weeks after the initial procedure and endoscopy alone at weeks 8, 10, and 12.. All of the gastrotomy closures with the septal occluder were successful. At follow-up endoscopy and laparoscopy there were no signs of adhesions, peritonitis, or perigastric abscess formation at the gastrotomy site. At 12 weeks, 5 of 6 animals were thriving, with appropriate weight gain.. Endoscopic gastrotomy closure with a septal occluder is technically feasible, safe, and effective in a survival porcine model.

Topics: Alloys; Animals; Disease Models, Animal; Equipment Design; Feasibility Studies; Follow-Up Studies; Gastroscopes; Gastroscopy; Heart Septum; Male; Prosthesis Design; Prosthesis Implantation; Stents; Stomach; Survival Analysis; Swine; Time Factors; Treatment Outcome

To test the feasibility of self-expanding drug-coated nitinol stents for prevention of restenosis in an animal model. Stent implantation in the carotid artery (CA) has been shown to be feasible for treatment of CA stenosis. Even though the restenosis rate in CA is reported to be lower than in the coronary and peripheral arteries, problems may arise with increasing numbers of treated patients and lengthier follow-up.. After predilatation with 8-mm balloons, 8 Goettinger minipigs were randomly selected to receive a sirolimus-eluting self-expanding nitinol stent (7 mm/80 mm) as well as the same stent without sirolimus/polymer coating in the right or left CA. Aspirin was given starting 3 days before the intervention and administered for an additional 4 weeks. Clopidogrel was administered for 10 days.. After 6 weeks, 2 subacute occlusions were observed in both groups. In the remaining vessels, the neointima was significantly reduced by sirolimus/polymer-coated stents (5.9+/-2.5 versus 0.7+/-1.0 mm2).. Sirolimus self-expanding nitinol stents may be an effective tool in reducing neointimal formation in CA.

Topics: Alloys; Angioplasty, Balloon, Coronary; Animals; Anti-Inflammatory Agents, Non-Steroidal; Aspirin; Atherosclerosis; Carotid Arteries; Clopidogrel; Coronary Angiography; Coronary Restenosis; Disease Models, Animal; Male; Polymers; Sirolimus; Stents; Swine; Ticlopidine; Time Factors; Ultrasonics

Three different internal airway stents were studied in an animal model of tracheomalacia: the Palmaz stent (Johnson & Johnson, Warren, New Jersey) and the NIR stent (Medinol Ltd., Tel Aviv, Israel)--both made of stainless steel in the form of tubular mesh--and the Nitinol stent, made of nickel-titanium formed into a spiral shape. All three stents could be adequately stabilized in the malacic tracheal segment. The Nitinol stent (Medinol Ltd., Tel Aviv, Israel) proved to be less reactive to the tracheal mucosa, demonstrated higher biocompatibility with significantly less granulation tissue formation, and showed superior radial resistance. Extraction of the Nitinol stent also proved to be much smoother. This stent may be the stent of choice in the treatment of tracheo- and bronchomalacia.

Topics: Airway Obstruction; Alloys; Animals; Bronchoscopy; Disease Models, Animal; Prosthesis Design; Stents; Swine; Trachea; Tracheal Diseases; Tracheal Stenosis

Topics: Alloys; Anastomosis, Surgical; Animals; Disease Models, Animal; Electrosurgery; Equipment Design; Equipment Safety; Kidney Calices; Laparoscopy; Random Allocation; Sensitivity and Specificity; Surgical Instruments; Swine; Ureter

To validate the deployment, in vivo performance, biostability, and healing capacity of the Anaconda self-expanding endoprosthesis in a canine aortic aneurysm model.. Aneurysms were surgically created in 12 dogs by sewing a woven polyester patch onto the anterior side of the thoracic or abdominal aorta. Anaconda prostheses were implanted transfemorally for prescheduled periods (1 or 3 months). Aneurysm exclusion and stent-graft patency were monitored angiographically. Healing was assessed with histological analysis and scanning electron microscopy (SEM). Textile analysis determined the physical and chemical stability of the woven polyester material, while the biostability of the nitinol wires was evaluated with SEM and spectroscopy.. All prostheses were intact at explantation. After 1 month, endothelial-like cells were migrating in a discontinuous manner both proximally and distally over the internal collagenous pannus at the device-host boundary. After 3 months, endothelialization had reached the midsections of the devices, with a thicker collagenous internal capsule. Patches of endothelial-like cells were sharing the luminal surface with thrombotic deposits. However, the wall of the device at the level of the aneurysm was generally poorly healed, with multiple thrombi scattered irregularly over the luminal surface. The polyester fabric was intact except for some filaments that were ruptured adjacent to the sutures and some abrasion caused by the nitinol wires. No evidence of corrosion was found on the nitinol stents.. This Anaconda stent-graft has demonstrated its ability to exclude arterial aneurysms. The device used in this study was an experimental prototype, and the manufacturer has incorporated new immobilization features into the model for clinical use. The constituent materials appear to be suitable in terms of biocompatibility, biofunctionality, and short-term durability.

Topics: Alloys; Angioplasty; Animals; Aortic Aneurysm, Abdominal; Blood Vessel Prosthesis; Blood Vessel Prosthesis Implantation; Corrosion; Disease Models, Animal; Dogs; Female; Male; Materials Testing; Polyesters; Prosthesis Design; Stents; Wound Healing

The Neuroform stent is a self-expanding nitinol stent designed for use in wide-necked intracranial aneurysms. Heating and imaging artifacts were evaluated by using a porcine carotid artery aneurysm model in a 3T MR system. A suspended Neuroform stent was tested for deflection. No heating was measured, and no evidence of deflection of the stent was found. Imaging artifacts were minimal. MR imaging in patients with Neuroform stent-treated aneurysms is safe and feasible.

Topics: Alloys; Animals; Artifacts; Carotid Artery Diseases; Contraindications; Disease Models, Animal; Equipment Failure Analysis; Equipment Safety; Heating; Intracranial Aneurysm; Magnetic Resonance Imaging; Phantoms, Imaging; Stents; Swine

Anticoagulation with warfarin for atrial fibrillation is frequently difficult. A transcatheter method to exclude the left atrial appendage from the circulation could be an advantage for selected patients. Percutaneous left atrial appendage transcatheter occlusion is a catheter-based delivery of an occlusive nitinol cage to the neck of the left atrial appendage. The device obliterates the left atrial appendage, eliminating a major source of thromboembolism. Animal studies have confirmed device coverage with an endocardial layer within 6 months and distal atrial appendage fibrosis. A standard transseptal approach from the right femoral vein is used. Patients leave the hospital within 1 day. Six-month follow-up of European and US safety and efficacy trials has shown favorable outcomes in minimizing thromboembolic events and few complications related to placement or healing of the device. Further clinical studies will be needed to establish which patients will be best treated with this device.

Topics: Age Factors; Aged; Aged, 80 and over; Alloys; Animals; Atrial Appendage; Atrial Fibrillation; Disease Models, Animal; Dogs; Echocardiography, Transesophageal; Humans; Middle Aged; Patient Selection; Prostheses and Implants; Risk Factors; Stroke

To evaluate a self-expanding rhenium 188 (188Re) radiochemically labeled radioactive stent in sheep.. A self-expanding nitinol stent (30 mm in length, 8 mm in diameter) coated with a functionalized polymer layer was radiolabeled with 188Re. Fifty prostheses, 25 of which were radioactive (mean radioactivity, 20 MBq +/- 3.8 [SD]) and 25 of which were nonradioactive, were implanted into the external iliac arteries of 25 sheep. Stent patency was assessed with angiography. Neointimal formation was assessed with intravascular ultrasonography and histologic examination 1 month (in all sheep) and 3 months (in 12 sheep) after implantation. The results were analyzed by using repeated-measures analysis of variance with two repeated factors and paired t tests for comparison at each measuring point.. All stents were placed successfully. Data in one animal had to be excluded from the study. After 3 months, a mean neointimal area reduction of 70 mm2 +/- 55 (SD) was observed inside the radioactive stents, and a mean lumen reduction of 126 mm2 +/- 39 was observed inside the nonradioactive control stents (P =.022). An edge effect was observed in the radioactive stents in that they showed an amount of neointimal formation at the edges that was similar to that seen in control stents. This neointimal formation accounted for the maximum lumen loss in the vascular segment with the stent.. As compared with a nonradioactive stent, a beta particle-emitting stent, through endovascular irradiation, significantly inhibits neointimal formation inside the stent but not at the stent edges.

Topics: Alloys; Animals; Coronary Restenosis; Disease Models, Animal; Follow-Up Studies; Prosthesis Implantation; Radioisotopes; Rhenium; Sheep; Stents; Tunica Intima

To evaluate the aneurysm volume and the intra-aneurysmatic pressure and maximal pressure pulse (dp/dtmax) in completely excluded aneurysms and cases with endoleaks.. In 36 mongrel dogs, experimental autologous aneurysms were treated with stent-grafts. All aortic side branches were ligated in 18 cases (group I) but were preserved in group II (n = 18). Aneurysm volumes were calculated from CT scans before and after intervention, and from follow-up CT scans at 1 week, 6 weeks and 6 months. Finally, for hemodynamic measurements, manometer-tipped catheters were introduced into the excluded aneurysm sac (group I and II), selectively in endoleaks (group II), and intraluminally for aortic reference measurement. Systemic hypertension was induced by volume load and pharmacologic stress. Pressure curves and dp/dt were simultaneously recorded and the ratios of aneurysm pressure to systemic reference pressure calculated.. At follow-up, type-II. endoleaks were excluded in all cases of group I by selective angiography. In contrast, endoleaks were evident in all cases of group II. Volumetric analysis of the aneurysms showed a benefit for group I with an improved aneurysm shrinkage: DeltaVolume + 0.08 %, - 1.62 % and -9.76 % at 1 week, 6 weeks and 6 months follow-up (median, group I), compared to + 1.43 %, + 0.67 %, and - 4.04 % (group II), p < 0.05. In case of complete aneurysm exclusion the ratio of systolic aneurysm pressure to systemic reference pressure was 0.662, 0.575 and 0.385 (median) at 1 week, 6 weeks and 6 months. The corresponding dp/dtmax ratios were 0.12, 0.07 and 0.04, respectively. However, within endoleaks selective measurements showed significantly increased pressure load: the ratios of systolic endoleak pressure to systemic reference pressure and the corresponding ratios for dp/dtmax were 0.882 and 0.913 (median), respectively. These hemodynamic findings were linear from hypotension, physiologic blood pressure to hypertension.. Occlusion of all aortic side branches of an aneurysm prior to stent-grafting reduces endoleaks and promotes aneurysm shrinkage. Complete aneurysm exclusion significantly reduces systolic pressure and dp/dt max. In contrast, endoleaks showed nearly systemic pressure load and undamped pulsatility.

Topics: Alloys; Angiography; Animals; Aortic Aneurysm, Abdominal; Blood Vessel Prosthesis; Blood Vessel Prosthesis Implantation; Data Interpretation, Statistical; Disease Models, Animal; Dogs; Follow-Up Studies; Hemodynamics; Stents; Time Factors; Tomography, Spiral Computed

Nitinol, a nickel-titanium alloy, is a valuable material in the construction of interventional endoluminal devices because of its biocompatibility, super elasticity, high resiliency and shape memory. The possibility of nickel toxicity has been raised with devices constructed of Nitinol. Our investigation examines the long-term corrosive behavior of this alloy in experimental and biological environments.. We performed three levels of study. Microscopic examination was made of 64 devices of various sizes, randomly selected from 240 Amplatzer Septal Occluders that had been exposed to saline solution at 37 degrees C for fourteen months. All samples were studied by electron microscopy ranging from 50 to 5000 times magnification. We also studied microscopically 3 Amplatzer devices explanted 18-36 months after implantation in dogs, and 2 Amplatzer Septal Occluders removed from patients 18 months (cardiac transplant) and 19 months (died of causes unrelated to device placement) after implantation, which were examined grossly and by electron microscopy up to 5000 times magnification. We then measured the levels of nickel in the blood using inductive plasma mass spectroscopy in 19 patients with implanted Amplatzer devices, making measurements before and 6 months after implantation.. Electron microscopy showed an intact titanium oxide layer with no evidence of corrosion in vitro and in vivo. One explanted device in direct contact with the platinum leads of a pacemaker for eighteen months showed minor pitting of the titanium oxide layer believed to be galvanic in nature. No wire fractures were found in vitro after cycle testing with 400 million cycles, nor in devices taken from the animals and humans. Biochemical studies showed no significant elevation of levels of nickel levels after implantation.. Nitinol wire of Amplatzer septal occlusion devices is resistant to corrosion when exposed to physiologic saline solution, and in experimental animals as well as humans. A device in contact with a platinum pacemaker electrode developed minimal pitting of the titanium oxide layer, believed to be galvanic in nature and of no structural or clinical significance. There is no increase of concentrations of nickel in the blood of patients who have received Amplatzer nitinol devices. These favorable testing results reveal that nickel-titanium is an inert, corrosion resistant alloy.

Topics: Adolescent; Adult; Alloys; Animals; Balloon Occlusion; Child; Child, Preschool; Corrosion; Disease Models, Animal; Dogs; Equipment Failure; Humans; Male; Models, Biological; Postoperative Complications; Time Factors; Vascular Diseases

Patients with endovascular stent implantation for the treatment of right ventricular outflow tract obstruction are often left with incomplete relief of the obstruction and significant pulmonary regurgitation. A noninvasive and reproducible method for monitoring such patients is desirable. MRI in the presence of a stent, however, has to overcome the problem of potential metallic artifacts.. Under x-ray fluoroscopic guidance, endovascular nitinol stents were placed across the pulmonary valve in 6 young pigs to induce pulmonary regurgitation. Five additional pigs served as controls. Initial MRI was performed after 2 days (13.5+/-1.8 kg) and follow-up after 3 months (32+/-2.9 kg). Pulmonary flow volumes and regurgitant fraction were quantified by velocity-encoded cine (VEC) MRI through (VEC-TS) and distal to (VEC-DS) the stent. VEC-TS was compared with VEC-DS and volumetric measurements of left and right ventricular stroke volumes provided by cine MRI ("gold standard"). Antegrade and retrograde pulmonary flow volumes by VEC-TS were slightly but significantly less than those with VEC-DS and cine MRI. Excellent correlations (r>0.97) for phasic pulmonary flow volumes as measured by VEC-TS and VEC-DS were shown. Pulmonary regurgitant fraction increased from 32.8+/-15% to 49.6+/-17% (P<0.05) over the course of 3 months with VEC-TS.. MRI demonstrates the progression of pulmonary regurgitation in growing swine. VEC MRI has the ability to quantify pulmonary blood flow inside the lumen of nitinol stents. MRI appears to be ideally suited for monitoring patients with endovascular nitinol stents in the pulmonary artery or pulmonary valve position.

Topics: Alloys; Animals; Artifacts; Blood Flow Velocity; Body Weight; Cardiac Output; Disease Models, Animal; Disease Progression; Electrocardiography; Follow-Up Studies; Heart Rate; Heart Ventricles; Magnetic Resonance Angiography; Magnetic Resonance Imaging, Cine; Pulmonary Artery; Pulmonary Circulation; Pulmonary Valve Insufficiency; Stents; Swine; Vascular Patency

To evaluate the short-term patency and healing characteristics of the Cragg EndoPro covered stent in an atherosclerotic model as one of the Food and Drug Administration requirements before possible approval of the device for human use in the United States.. Seventeen self-expanding stent-grafts were placed in the aorta and right and left iliac arteries of six Yucatan microswine exposed to a regimen of accelerated atherosclerosis. The stent-grafts were constructed from nitinol wire formed into a tubular zigzag configuration. The stent frame was covered by a thin woven polyester fabric tube, with medium permeability, available in multiple diameters and lengths. The animals were killed at 24 hours, 3 months, and 6 months. Assessment was done by angiography and histology.. All stents were patent immediately after deployment. Two stents were occluded at follow-up, indicating an 88% patency rate. Minor lumen narrowing was found at the follow-up intervals. Histologic examination revealed a mixture of mature and immature endothelial cells lining both the native and stented regions in all vessels examined. The new endoluminal surface was composed primarily of fibrocollagen and elastic fibers and smooth muscle cells. Intimal thickness was inversely correlated to medial thickness. Medial compression with atrophy was observed routinely with rare necrosis. Complete tissue ingrowth was seen by 3 months. The degree of vascular inflammation increased over time, as well as the foreign body giant cell reaction to the polyester fabric.. The patency rate does not appear to be better than that with angioplasty or noncovered stent placement in the studied time frame. The progressive vascular inflammatory changes noted should be further investigated in longer-term animal trials to ensure its safety in humans because this device is meant to be permanent.

Topics: Alloys; Animals; Arteriosclerosis; Disease Models, Animal; Female; Postoperative Complications; Stents; Swine

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

Transcatheter closure of a membranous ventricular septal defect (MVSD) is much more difficult than closure of other intracardiac defects because of the proximity to the aortic and tricuspid valves and their relatively large size in small children. In this report, transcatheter closure of naturally occurring membranous VSDs was attempted in 12 Yucatan minipigs. The prosthesis is constructed from fine Nitinol wires in the shape of two buttons and a connecting waist filled with polyester fiber. Two kinds of prosthesis were used in this study: concentric and eccentric left-sided retention disks. A 6 or 7 Fr delivery sheath was advanced across the membranous VSD over a wire from femoral vein. The prosthesis was inserted through the sheath by pushing the delivery cable to deploy a button into left ventricle and the second button was then deployed into right ventricle by withdrawing the sheath. Successful implantation of the device was achieved in all animals except one. Complete closure rate was 58.3% immediately after placement, 100% at 1 week, 90.9% at 1 month and 3 months, and 100% at 6 months. An associated aneurysm of the membranous septum increased significantly in size in two of three animals using the concentric device, and in none of the animals using the eccentric device. A trace to mild aortic regurgitation was present in two of the three animals using the concentric device, and only in one of the eight animals using the eccentric device. Five animals developed a trace to mild tricuspid regurgitation. Pathologic examination showed all devices to be covered by smooth neoendothelium at 3 months. This report presents the first experimental study where closure of membranous ventricular septal defects in a swine model was attempted by specially constructed devices. Procedural success and occlusion rates are very encouraging but overall results cannot equal surgery. Further experimentation is needed with devices that are redesigned according to the experience gained from this study.

Topics: Alloys; Angiography; Animals; Biocompatible Materials; Cardiac Catheterization; Disease Models, Animal; Heart Septal Defects, Ventricular; Prosthesis Design; Prosthesis Implantation; Stents; Swine, Miniature

To observe the effect of V-shaped nitinol alloy implantation into the acetabular roof of puppies with acetabular dysplasia on acetabular dysplasia.. The puppies with acetabular dysplasia were divided randomly into two groups. Osteotomy was begun about 0.5 cm above the acetabulum, using a curved osteotome this cut must proceed between the medial wall of the ilium and medial wall of the acetabulum. The osteotomy does not have to be carried to the triradiate cartilage. When the osteotomy is completed, the superior aspect of the acetabulum can be hinged downward by curved osteotome. The V-shaped nitinol alloy was wedged securely in the osteotomy site. Roentgenogram was made 4 and 12 weeks after operation in all animals.. The inclination of the acetabular roof was redirected and the acetabular index was decreased. Microscopic study showed a marked proliferation of cartilaginous cells of the acetabular cartilage.. The V-shaped nitinol alloy implantation into the acetabular roof can correct the sloping acetabular roof, increase the coverage on the femoral head, and improve the growth of the acetabulum.

Topics: Acetabulum; Alloys; Animals; Braces; Disease Models, Animal; Dogs; Female; Hip Dislocation, Congenital; Male; Osteotomy; Prostheses and Implants; Random Allocation

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

This experimental study was conducted to evaluate neointimal thickness, lumen diameters, and histologic changes in normal and stenotic porcine iliac arteries following placement of self-expanding nitinol Strecker stents.. Neointimal trauma causing slight vascular stenosis was induced unilaterally within external iliac arteries of 12 swines by means of endothelial abrasion and high cholesterol diet. Nitinol Strecker stents were placed within the stenotic and the normal contralateral vascular segments. For histopathologic evaluation, the pigs were killed 12 or 24 weeks after stent placement and luminal diamters were evaluated angiographically.. Excluding one occlusion, 15% narrowing of the lumen diameter was induced unilaterally (P = .002). Initial luminal gain after stent placement was greater for stenotic than for normal arteries. The amount of neointima thickness was not different between stenotic and normal vessels (P > .05). Comparing vascular diameters before stent placement and at follow-up, luminal loss due to neointima proliferation was 22% within normal arteries (P = .0002), while a luminal gain by 15% was found within the stenotic arteries (P = .008). Maturation of neointima and endothelial coverage were complete after 24 weeks.. Even though nitinol Strecker stents induce excessive neointimal proliferation, stenotic arteries seem to profit from great early luminal gain resulting in 15% of vascular expansion at follow-up while slight stenosis is induced within normal iliac arteries.

Topics: Alloys; Angiography; Animals; Arterial Occlusive Diseases; Blood Vessel Prosthesis Implantation; Disease Models, Animal; Female; Follow-Up Studies; Iliac Artery; Stents; Swine; Treatment Outcome; Tunica Intima

Self-expanding spiral nitinol stents are potentially removable and may be useful in the treatment of benign strictures. We evaluated the histologic response to stent placement and technical aspects of their placement and removal in a porcine model.. Nine animals were studied. Stents were placed above the papilla in six surviving animals. After intervals of one, two or three months cholangiography and attempted stent removal was performed. Four animals were then sacrificed acutely with their stent in place, and two were sacrificed after a one-month healing interval. The results of placement, follow-up cholangiography and histology are reported.. Cholangiography and stent placement succeeded in 26 of 27 and 11 of 16 attempts, respectively. Three placement failures were attributed to stent/duct size disparity or a faulty release mechanism, resulting in stent kinking and/or duct twisting. Among the successfully deployed stents, two animals developed strictures where stents traversed bifurcations and one exhibited partial luminal compromise by tissue entrapment between coils. Fluoroscopically guided removal was successful in two of five stents positioned above the papilla. Histology was non-specific but minimally changed in those given a one-month healing interval after removal. Others exhibited moderate inflammation, fibrosis and an intramural abscess at sites of induced stricture.. Spiral metal stents for the treatment of benign strictures remain experimental. Care must be taken to deploy them in bile ducts of adequate diameter and endoscopic removal is not yet demonstrably reliable and safe.

Topics: Alloys; Animals; Bile Ducts; Biliary Tract Diseases; Cholangiography; Constriction, Pathologic; Disease Models, Animal; Evaluation Studies as Topic; Prosthesis Design; Stents; Swine

Repair of muscular ventricular septal defects (MVSDs) has always been challenging to the surgeon. Long-term morbidity and mortality are significantly increased if the defects are closed via left ventriculotomy or if they are associated with other complex congenital anomalies. The purpose of this study was to close MVSDs with the Amplatz ventricular septal defect device. This device is constructed from 0.004-in nitinol wire mesh filled with polyester fibers. It is retrievable, repositionable, self-centering, and of low profile.. MVSDs were created with the help of a sharp punch in 10 dogs. The location of the defects was anterior muscular (n=3), midmuscular (n=3), apical (n=3), and inlet muscular (n=1). The diameter of the defects ranged from 6 to 14 mm. All defects were closed in the catheterization laboratory. The device was placed with the help of transesophageal echocardiography and fluoroscopy. A 7F sheath was used to deploy the device from the right ventricular side in 8 and the left ventricular side in 2 dogs. Placement was successful in all animals. The complete closure rate was 30% (3/10) immediately after placement and 100% at 1-week follow-up. Pathological examination of the heart revealed complete endothelialization of the device in dogs killed after 3 months.. The Amplatz ventricular septal defect device appears highly efficacious in closing MVSDs. The advantages include a small delivery sheath, complete retrievability before release, and the fact that it is self-centering and self-expanding, thereby making it an attractive option in smaller children.

Topics: Alloys; Animals; Cardiac Surgical Procedures; Coronary Angiography; Disease Models, Animal; Dogs; Echocardiography, Transesophageal; Endocardium; Fluoroscopy; Follow-Up Studies; Heart Septal Defects, Ventricular; Heart Ventricles; Time Factors

Stenting is increasingly being used to treat carotid artery disease. However, complications including distal embolization, stent thrombosis, stent collapse from external compression, the need for high-pressure inflation with increased neointimal response, or balloon rupture during stent expansion and stent loss are all potential problems and of concern. To address each of these specific concerns, a new stent was designed, which is self-expandable, made of nitinol, with temperature-dependent superelastic properties, and with high vessel wall surface coverage. Since this device has a number of novel characteristics, we aimed to assess the short- and long-term histopathologic response in pig carotid and iliac arteries. Single stents were deployed in pig carotid and iliac arteries after overstretch balloon injury. Angiograms were performed pre- and poststenting and prior to sacrifice. Intravascular ultrasound was used before implantation to determine vessel size. Vessels were examined histologically at 1 month (n = 6) and 6 months (n = 6) for morphometric analysis, hemorrhage and thrombus, endothelialization, and inflammatory and fibrotic responses. There was a 100% angiographic success rate at implantation. In one case, it was determined histologically that a single stent was implanted in a dissection plane of a pig's left iliac artery and was occluded by organized thrombus, with the true lumen being patent. At 6-month follow-up, this was the only evidence of a single stent occlusion, with flow adjacent to the stent in the true lumen. In the other vessels, the stents showed good vessel wall-stent apposition and the lumens were patent with a concentric and thin neointima. Inflammatory cells were rare and there were no mural thrombi. Coverage of the vessel wall by endothelial-like cells was complete at 1 month. The novel nitinol EndoStent appears to have favorable biocompatibility with minimal thrombus deposition or inflammatory response, and its use is feasible for clinical application in carotid and iliac arteries.

Topics: Alloys; Animals; Arterial Occlusive Diseases; Biocompatible Materials; Blood Vessel Prosthesis Implantation; Carotid Arteries; Disease Models, Animal; Follow-Up Studies; Iliac Artery; Prosthesis Design; Stents; Swine

Flexible nephroscopes and ureteroscopes make it possible to see calculi in remote calices, but it is often impossible to remove these with existing technology. Flat-wire baskets impede deflection and can traumatize the papilla. This study compares the performance of a new 3.2F tipless nickel-titanium (Nitinol) basket with that of an existing 3.0F flat-wire basket. Specifications were compared using a 15F nephroscope and a 7.5F flexible ureteroscope in a pig kidney model. A calculus was placed in a calix, and the author and two residents were timed while using both baskets to retrieve the stone. To open fully, the flat-wire basket needed to protrude 1.2 cm further than the tipless basket. The tipless basket did not restrict deflection of the nephroscope, whereas the flat-wire basket limited flexion by 24 degrees and extension by 28 degrees. The tipless basket did not restrict extension of the 7.5F ureteroscope but limited flexion by 10 degrees. The flat-wire basket limited flexion by 79 degrees and extension by 72 degrees. Using the pig kidney model, the three operators took a mean of 5.3, 11.8, and 6.4 seconds to catch the stone with the tipless basket. Using the flat-wire basket, the mean times were 15.3, 34.5, and 28.9 seconds (combined data: 8.2 seconds for the tipless basket and 27.8 seconds with the flat-wire basket; P = 0.0001). Only the flat-wire basket was seen to traumatize the papilla. The Nitinol tipless basket has significant advantages over the flat-wire basket.

Topics: Alloys; Animals; Disease Models, Animal; Endoscopes; Evaluation Studies as Topic; Kidney Calculi; Materials Testing; Swine; Ureteroscopes

To define the safety and efficacy of a pneumatically driven, mechanical lithotriptor using nitinol probes through semirigid and actively deflectable, flexible fiberoptic endoscopes.. The Browne Pneumatic Impactor (BPI) uses standard compressed air to drive a nitinol wire along its long axis onto a calculus, fragmenting it. Bench top and in vivo experiments were designed to explore variables, including the effects of various nitinol probe tip designs, outer diameters, excursion distances, and sheathing materials as well as the efficiency of fragmentation with active endoscope deflection. In vivo experiments in two animal models (porcine and canine) were performed using small diameter, fiberoptic semirigid, and actively deflectable, flexible ureteroscopes. Surgically placed calculi were fragmented with the BPI and representative tissue was obtained immediately and up to 2 weeks postoperatively to define histologic changes. A panel of human urinary calculi was chosen for their relative difficulty in fragmentation with other modalities.. Calculi, including pure calcium oxalate monohydrate, brushite, cystine, and triamterene, were fragmented with the BPI used through both semirigid and actively deflectable, flexible endoscopes. A rounded tip design and excursions of 1 mm fragmented calculi most efficiently with minimal histologic reaction. Retrograde stone migration before fragmentation was noted in dilated upper urinary tracts. This was prevented by first entrapping the calculus within a standard basket. Ureteral calculi were fragmented with the nitinol probes deflected up to 45 degrees by the flexible endoscope. With increased active deflection, the efficiency of fragmentation decreased.. The BPI represents a safe, thermal-free endoscopic lithotrite able to fragment the hardest calculi through semirigid and flexible ureteroscopes.

Topics: Alloys; Animals; Disease Models, Animal; Dogs; Equipment Design; Fiber Optic Technology; Lithotripsy; Swine; Ureteroscopy; Urinary Calculi

Topics: Alloys; Anastomosis, Surgical; Animals; Digestive System Surgical Procedures; Disease Models, Animal; Dogs; Equipment Design; Gastrointestinal Diseases; Humans; Suture Techniques; USSR; Wound Healing