Multilayer Stent Research Articles

Hemodynamics and Oxygen Transport through Pararenal Aortic Aneurysm Treated with Multilayer Stent: A Numerical Study

As opposed to an endoluminal stent graft, a multilayer stent (MS) consists of a porous mesh, which allows for the possibility of treating pararenal aortic aneurysms (PRAAs) that involve a significant branch vessel. However, the choice of the density of the MS plays a vital role in isolating the aneurysm and allowing unobstructed blood flow in the branch vessel. In the present study, we examined 3 cases (without a stent and with single-layer and double-layer stents) via numerical simulations to explore the feasibility of the MSs used in the treatment of such aneurysms and estimate whether there is a more appropriate or optimal stent density. With stent intervention, the velocity of blood flow in the sac decreased, but the pressure on the surface of the aneurysm did not decrease although it became more uniform. In addition, the "region of double low" (with low wall shear stress and a low Sherwood number) enlarged after stent implantation. Even with the double-layer stent, however, the flux of the branch vessel was still above normal, and we could predict that the optimal stent porosity was approximately 49.9%. Unlike in previous studies, an MS could not be feasibly applied to high-risk PRAAs. However, an MS can induce sac thrombosis in the later stages while maintaining visceral vessel patency, and our results suggest that the optimal stent may be a 4-layer stent.

Investigation of the hemodynamics of a juxtarenal aortic aneurysm with intervention by dual-stents strategy

ObjectiveTo study the feasibility of using two stents (a combination of multilayer stent [MS] and stent graft [SG]) in the treatment of a juxtarenal aortic aneurysm that involves a significant branch artery and to determine the advantages and disadvantages of using SGs upstream and downstream from the aneurysm so as to provide some theoretical guidance for preoperative clinical decision-making in the future. MethodsFour ideal geometric models were established for numerical computation: case 1 refers to an aneurysm without the use of stents, case 2 represents the implantation of two MSs in an aneurysm, and case 3 (SG + MS) and case 4 (MS + SG) both involve the treatment of an aneurysm by using a combination of SG and MG. ResultsThe aneurysm pressure is slightly lower and there are more vortices when the SG is implanted (case 3 and case 4). In particular, for case 4, additional vortices appear in the sac and the area of the low-wall shear stress is larger on the aneurysm compared with those of the other three cases. However, the pressure becomes uneven, and a peak pressure region is observed on the wall of the aneurysm, and therefore, the aneurysmal wall will become buckled. In addition, the flux of the renal artery in the four cases is greater than that in the normal case. ConclusionThe arrangements in cases 3 and 4 can effectively isolate the aneurysm from circulation, but clinically, it is necessary to avoid such a high-risk situation wherein the SG is positioned downstream of the aneurysm (case 4), even though this leads to improved isolation.

Visceral artery aneurysms - classification, diagnosis and treatment.

Although visceral artery aneurysms are rare, mortality due to their rupture is high, estimated at even 25–75%. That is why it is significant to detect each such lesion. Visceral artery aneurysms are usually asymptomatic and found incidentally during examinations performed for other indications. Autopsy results suggest that most asymptomatic aneurysms remain undiagnosed during lifetime. Their prevalence in the population is therefore higher. The manifestation of a ruptured aneurysm depends on its location and may involve intraperitoneal hemorrhage, gastrointestinal and portal system bleeding with concomitant portal hypertension and bleeding from esophageal varices. Wide access to diagnostic tests, for example ultrasound, computed tomography or magnetic resonance imaging, helps establish the correct diagnosis and a therapeutic plan as well as select appropriate treatment. After a procedure, the same diagnostic tools enable assessment of treatment efficacy, or are used for the monitoring of aneurysm size and detection of potential complications in cases that are ineligible for treatment. The type of treatment depends on the size of an aneurysm, the course of the disease, risk of rupture and risk associated with surgery or endovascular procedure. Endovascular treatment is preferred in most cases. Aneurysms are excluded from the circulation using embolization coils, ethylene vinyl alcohol, stents, multilayer stents, stent grafts and histoacryl glue (or a combination of these methods).

Contemporary strategies for repair of complex thoracoabdominal aortic aneurysms: real-world experiences and multilayer stents as an alternative.

Thoracoabdominal aortic aneurysms (TAAA) present special challenges for repair due to their extent, their distinctive pathology, and the fact that they typically cross the ostia of one or more visceral branch vessels. Historically, the established treatment for TAAA was open surgical repair, with the first procedure reported in 1955. Endovascular repair of TAAA with fenestrated and/ or branched endografts, has been studied since the beginning of the current century as a means of mechanical aneurysm exclusion. More recently, flow modulator stents have been employed with the aim at reducing shear stress on aortic aneurysmal wall. In this review we present technical and main results of these techniques, based on literature review and personal experience.

The multilayer flow modulator stent (MFM) for the treatment of complex aortic aneurysms. Indications–contraindications – Results

The multilayer flow modulator stent (MFM) for the treatment of complex aortic aneurysms. Indications–contraindications – Results

Open and endovascular treatment by covered and multilayer stents in the therapy of renal artery aneurysms: mid and long term outcomes in a single center experience.

The purpose of this paper is to evaluate the mid and long terms outcomes of open and endovascular surgical treatment, as well as multilayer stent, in patients affected by Renal Artery Aneurysm (RAA). Twenty five patients with RAA (24 monolateral and 1 bilateral aneurysm, 26 aneurysms) were observed between 2000 and 2015: 4 were not treated due to the small size of the aneurysm (< 2.5 cm); out of the remaining, 16 underwent endovascular treatment, 2 were treated by open surgery consisting in aneurysmectomy and graft reconstruction and 5 (in 1 patient bilateral) were treated by ex vivo repair and autotransplantation. Out of the 22 patients treated for RAA, one patient operated upon open surgery presented an early thrombosis of a PTFE graft, followed by nephrectomy (4.7%); one patient underwent autotransplantation showed an ureteral kinking without functional consequences. In a follow-up ranging from 1 and 11 years (mean 5 years), no deaths were observed; all the renal arteries repaired were patents and 16 out of 21 patients had a significative reduction of systemic blood pressure. The choice of the best treatment is based on aneurysm's morphology according to Rundback's classification. The type I, involving the main renal artery, is always treated by endovascular approach; type II, involving renal artery bifurcations may be treated by open surgery or multilayer stents; type III (hilar or intraparenchymal aneurysms) needs only an open surgical treatment as autotransplantation. Based on our experience it seems that most of RAAs may be treated by endovascular technique. The ex vivo autotransplantation represents the first-line treatment in hilar and intraparenchymal aneurysms. Multilayer stents seem to have good outcome in the treatment of aneurysms involving arterial bifurcations. Mid and long term results, related to kidney preservation and to normalization of blood pressure, seems satisfying.

Hemodynamics study of a multilayer stent for the treatment of aneurysms.

BackgroundThe changes of hemodynamics caused by the implantation of multilayer stent (MS) have significant effects for aneurysm sac.MethodsComparisons of 3D numerical models with/without a MS in an abdominal aortic aneurysm with a 90° branch vessel were numerically studied from the viewpoint of hemodynamics.ResultsThe results showed that: (1) The flow fields and Wall Shear Stress (WSS) are changed dramatically after MS implantation. The velocity of the blood flow in aneurysm sac decreases significantly and the regions of low-WSS increase. These help thrombus formation; (2) The pressure in aneurysm slightly decreases and keeps close to the normal level of blood pressure, however the risk of aneurysm enlargement or even rupture still exists; (3) The flux and the velocity in branch artery are reduced by about half after MS implantation. Due to the implantation of MS, the changes in the flow field causes the decrease of pressure/WSS in aneurysm sac and the blood flow in branch vessel.ConclusionsThe implantation of MS into abdominal artery results in more low-WSS regions inside aneurysm which induces thrombus formation. The pressure is reduced slightly means the risk of aneurysm rupture exists.

A numerical framework for the mechanical analysis of dual-layer stents in intracranial aneurysm treatment

Dual-layer stents and multi-layer stents represent a new paradigm in endovascular interventions. Multi-layer stents match different stent designs in order to offer auxiliary functions. For example, dual-layer stents used in the endovascular treatment of intracranial aneurysms, like the FREDTM (MicroVention, CA) stent, combine a densely braided inner metallic mesh with a loosely braided outer mesh. The inner layer is designed to divert blood flow, whereas the outer one ensures microvessels branching out of the main artery remain patent. In this work, the implemented finite element (FE) analysis identifies the key aspects of dual-stent mechanics. In particular, dual-layer stents used in the treatment of intracranial aneurysms require the ability to conform to very narrow passages in their closed configuration, while at the same time they have to provide support and stability once deployed. This study developed a numerical framework for the analysis of dual-layer stents for endovascular intracranial aneurysm treatment. Our results were validated against analytical methods. For the designs considered, we observed that foreshortening was in average 37.5%±2.5%, and that doubling the number of wires in the outer stent increased bending moment by 23%, while halving the number of wires of the inner stent reduced von Mises stress by 2.3%. This framework can be extended to the design optimization of multi-layer stents used in other endovascular treatments.

Treatment of Complex Aorta Diseases by Multilayer Stents

Purpose: The aim of our study was to evaluate the role of multilayer stents (MLS) in the therapeutic arsenal of complex aortic pathologies for frail patients combining several comorbidities that are initially objected to the conventional surgical treatment. Materials and methods: Since March 2012, we conducted a monocentric prospective study on a series of 41 procedures, performed on 41 aortic lesion locations in 38 patients treated with multilayer stents. The series was divided into four groups. The first group included 21 cases: 20 thoracoabdominal aneurysms and one aneurysm of the entire descending thoracic aorta. The second group included 7 cases of juxta/infra renal aneurysms, the third group included 5 cases of false aneurysms and the fourth group included 8 cases of aortic dissecting hematoma (first subgroup: 6 cases) or extended dissections (second subgroupe: 2 cases).Three patients were treated during the same operation for a double aneurysm location (thoracic and abdominal in 2 cases and aortic arch and thoracic aorta in the 3rd case). Results: The series included 25 men and 13 women with an average age of 63 years (40-84 years). The procedures were performed under local anesthesia in 3 cases, loco regional in 19 cases and general anesthesia in 16 cases. The average hospital stay was 7 days (4-14 days).The technical placement of the MLS was successful for the 41 procedures. No paraplegia, no stroke and no mesenteric ischemia occurred. Three complications related to the surgical approach were treated surgically with success. Two patients had post-operative renal failure for which one required dialysis. The 30-day mortality in relation to the aneurysm was 3% (one case of rupture in the first postoperative day) and unrelated to the aneurysm 3% (one case of massive myocardial infarction after the procedure). For an average follow up of 12 months (1-20 months) mortality unrelated to the aneurysm was 25% (9 deaths) and 0% in relation to the aneurysm. Among the 38 remaining aortic lesions treated and followed, the aneurismal sac was not feeded in 14 cases (63%) with 6 out of 20 cases in group 1(30%), 3 out of 6 cases in group 2(50%), 3 out of 4 cases in group 3 (75%) and finally 2 out of 6 cases in the first subgroup of group 4 (33%). The aneurismal sac is not feeded in 19 cases (50 %), including 14 out of 20 cases in group 1 (70%), 2 out of 6 cases in group 2 (33%), 1 out of 4 cases in the group 3(25%) and 2 out of 6 cases in the first subgroup of group 4 (33%). Two cases of extensive dissections treated remained stable without aneurismal changes. Three cases are recent: 1 out of 6 cases in group 2 (17%) and 2 out of 6 (33%) in the first subgroup of group 4 (33%). Visceral arteries and supraaortic trunks remained patent in all the 38 cases. Conclusion: MLS may be an option treatment for dissections and complex aortic aneurysms in frail patients with high surgical risk. Our results showed that better results are obtained for false aneurysms and true aortic aneurysms without involvement of significant side branches.

Endovascular treatment of aortic lesions involving branch vessels with multi-layer bare stents

Aortic lesions involving branch vessels have always been a great challenge for vascular surgeons. Endovascular repair are growing to take place of traditional open repair for less invasion and lower complication rates. Despite rapid developments in endovascular instruments have been achieved in the last decade, and endovascular techniques such as fenestration stents have been applied in the treatment of aortic lesions involving branch vessels. However, endovascular repairing aortic lesions involving branch vessels remains being restricted by rigorous indication selection as well as requirements of advanced experiences and sophisticated skills. Recently, several studies about treating aortic lesion involving branch vessels with multi-layer bare stents have been reported, the primary results were encouraging and brought new visions for the management of such disease. More approving clinical evidences about the safety and efficacy of multi-layer stents are anticipated.

TCT-777 The Multilayer Flow Modulator Stent For The Treatment Of Thoraco Abdominal And Abdominal Aortic Aneurysms. Moroccan Experience

Thoraco Abdominal Aortic Aneurysms (TAAA) and Abdominal Aortic Aneurysms (AAA) are traditionally treated surgically, but more and more by interventional procedures (endografts, fenestrated, branched grafts, chimney techniques). We used a new concept of stent, the Multilayer Stent Flow Modulator (M.F

Early and Intermediate Results of Elective Endovascular Treatment of True Visceral Artery Aneurysms

To retrospectively analyze early and follow-up results of endovascular management of visceral artery aneurysms (VAAs) in a single-center experience. From 2007 to June 2013, 26 consecutive elective endovascular interventions for VAAs were performed in 26 patients; preoperative, intraoperative, and postoperative data were prospectively collected in a dedicated database. Early (<30 days) and follow-up results were evaluated. The site of aneurysm was splenic artery in 17 patients, common hepatic artery in 3 patients, renal artery and pancreaticoduodenal artery in 2 cases each, and gastroduodenal artery and celiac trunk in one case each. All the lesions were asymptomatic, and the mean diameter was 22.8 mm. Interventions consisted in coiling in 19 cases; in 4 patients a covered stent was placed, whereas the remaining 3 patients had a multilayer stent. Technical success was 89%. There were no perioperative deaths; 1 patient with splenic artery aneurysm had coils migration with symptomatic splenic infarction and underwent successful redo coils packing. Median duration of follow-up was 18 months. During follow-up, 1 aneurysm-unrelated death occurred. One asymptomatic thrombosis of a treated vessel was recorded, with a 2-year estimated patency rate of 91%. Mean aneurysmal diameter at the latest follow-up was 20.2 mm (P = 0.001 in comparison with preoperative values; 95% confidence interval 1.9-5.2). Complete exclusion of the aneurysm occurred in all but 1 patient, who had a limited increasing in the diameter of its splenic aneurysmal sac after coiling. Another patient developed a more distal aneurysm of the splenic artery after 24 months. No reinterventions were required. Freedom from aneurysm-related complications at 2 years was 72.9% (Standard Error, 0.09). In our experience, endovascular treatment of VAA, when feasible, provided excellent perioperative results with low rates of complications and reinterventions. Even if the risk of developing aneurysm-related complications during follow-up is substantial, most of them can be watched without the need for repeated interventions.

The use of the Cardiatis multilayer flow modulator stent to treat sequential saccular aneurysms of the renal artery in a solitary kidney

The use of the Cardiatis multilayer flow modulator stent to treat sequential saccular aneurysms of the renal artery in a solitary kidney

Endovascular repair of a juxtarenal saccular aneurysm using the Multilayer Flow Modulator: report of the first case performed in a Public Hospital in Brazil

Endovascular treatment of abdominal aortic aneurysms (AAA), involving the exits of the renal and visceral arteries still constitutes a considerable challenge. Many different techniques have been developed over the years in attempts to surmount the difficulties presented by these cases. Techniques that have gained prominence include fenestrated or branched stents, methods involving parallel prostheses, such as the chimney, periscope and sandwich techniques, and, more recently, flow modulation with Multilayer stents. We describe a case of a complex juxtarenal saccular AAA with a high surgical risk, both according to cardiological assessment and because the patient had a difficult airway caused by a total laryngectomy for early stage laryngeal neoplasm. In view of the technical simplicity of using Multilayer stents, the presence of chronic obstructive aortoiliac disease, ostial stenosis of the renal artery and a small diameter suprarenal aorta, options involving fenestrated/branched stents and techniques involving parallel prostheses were ruled out, because of the need for multiple accesses. In view of the dilemma it presented, we describe this case as a therapeutic challenge and present the treatment option employed, which has been successful over the short term.

TCT-572 A NEW CONCEPT OF STENT: THE MULTILAYER FLOW MODULATOR STENT FOR THE TREATMENT OF THORACO ABDOMINAL AND ABDOMINAL AORTIC ANEURYSMS.

Thoraco Abdominal Aortic Aneurysms (TAAA) and Abdominal Aortic Aneurysms (AAA) are traditionally treated surgically, but more and more by interventional procedures (endografts, fenestrated, branched grafts, chimney techniques). We used a new concept of stent, the Multilayer Stent Flow Modulator (M.F

Aortic Aneurysm Rupture Following Treatment With Flow-Diverting Multilayer Stents

Aortic Aneurysm Rupture Following Treatment With Flow-Diverting Multilayer Stents

Endovascular Repair of a Complex Splenic Artery Aneurysm Using a Multilayer Stent.

To the Editor, Based on autopsy studies, the prevalence of visceral artery aneurysms has been estimated to be up to 10 % [1], with up to 25 % complicated by rupture and a mortality rate of up to 70 % [2]. Splenic artery aneurysms (SAA) account for *60 % of visceral artery aneurysms [2]. Asymptomatic SAA larger than 2 cm should be treated either by operation or endovascular techniques [3, 4]. In recent years, exclusion of aneurysms by implanting multilayer stents is considered an attractive, minimally invasive treatment option [5–9]. Due to the multilayer design of this vascular prosthesis, the tubular, self-expanding multilayer stent (Cardiatis, Isnes, Belgium) is supposed to decrease velocity and vorticity of intra-aneurysmal blood flow. Thereby, thrombus formation within the aneurysm sac shall be deemed over time. The affected main artery and moreover branching vessels deriving from the aneurysm or the proximal and distal landing zones are expected to remain patent due to preserving laminar flow. We hereby report a successful minimally invasive treatment of a complex SAA with a multilayer stent. In a 46-year-old woman, a SAA was incidentally found after ultrasound examination at her general practitioner. Computed tomography angiography (CTA) showed a fusiform aneurysm in the distal part of the splenic artery with a maximum diameter of 2 cm and an ectatic transformation of the proximal and especially distal subsequent splenic artery over a total length of *4 cm. In a first angiographic effort in an attempt to use a balloonexpandable stent-graft, elongation and consecutive tortuosity of the splenic artery made any attempt for pushing the stent-graft forward impossible. In a multidisciplinary consensus, endovascular repair with the new multilayer stent was favored over open surgery. Before interventional therapy, the patient gave written informed consent. Digital subtraction angiography was performed using a left transbrachial approach. A 90-cm long, 7F sheath (Destination, Terumo, Tokyo, Japan) was introduced, and the splenic artery was engaged via a 4F catheter in multipurpose configuration (Cordis Corporation, Bridgewater,

Treatment of Visceral Aneurysm Using Multilayer Stent: Two-Year Follow-Up Results in Five Consecutive Patients

The present study was performed to analyze the midterm results (five consecutive patients, 2-year follow-up) of the endovascular management of visceral artery aneurysms using the Cardiatis Multilayer Flow Modulator (CMFM) (Cardiatis, Isnes, Belgium), a self-expandable stent. From August 2009 to January 2011, we implanted five CMFMs in five patients (all men; mean age 73 years) to treat two common hepatic artery aneurysms, one celiac trunk aneurysm, one splenic artery aneurysm, and one superior mesenteric artery aneurysm (diameter 25-81 mm). The primary end point was technical success. The secondary end point was stent patency, absence of aneurysm rupture or reperfusion, and shrinking of the sac at 6-, 12-, and 24-month follow-up using computed tomography angiography. Follow-up ranged from 24 to 48 months (mean 31.2). Technical success was achieved in all patients. Complete exclusion of the aneurysm with sac shrinking was achieved in two patients. Two stents became occluded at 6- and 24-month follow-up, respectively; both patients were asymptomatic and were not retreated. One patient developed sac reperfusion due to incomplete aneurysm exclusion. Long-term results in a wider population are needed to validate the effectiveness of the CMFM.

Treatment of Primary Infected Juxtarenal Aortic Aneurysm With the Multilayer Stent

To report the use of multilayer uncovered stent to treat primary infected juxtarenal aortic aneurysm. A 50-year-old man was admitted to hospital for rapid onset of intractable abdominal pain and high fever. Computed tomographic scan showed 2 juxtarenal saccular aneurysms of abdominal aorta with morphologic and clinical changes compatible with infectious etiology. Patient was treated with multilayer flow-modulating stent. Follow-up imaging showed persistent aneurysm exclusion and continuous aneurysm shrinkage of the sac until complete regression to a normal aortic configuration was seen at 1 year. During follow-up (24 months), patient continued to do well, and there was no recurrence of infection. Multilayer stent appeared to be an acceptable treatment option for primary infected juxtarenal aortic aneurysms. Aneurysmal sac completely disappeared and visceral branches remained patent at 2-year follow-up. However, longer follow-up is necessary to evaluate the long-term patency of involved visceral arteries.

Disconnection of Multilayer Stents 2 Years After Treatment of a Hepatic Artery Aneurysm

To report midterm failure of tandem peripheral multilayer stents used to treat a common hepatic artery aneurysm (HAA) that had a good early result. A 71-year-old man with multiple comorbidities had a 3.4-cm HAA treated with 2 Cardiatis peripheral multilayer stents (8×100 and 9×60 mm) that overlapped by 3 cm. At the 12-month follow-up, the stents were patent, with signs of collateral patency and full thrombosis of the aneurysm sac without expansion. At the 18-month visit, the sac had expanded to 4.5 cm without signs of revascularization, but there was an initial stent dislocation; a wait and watch approach was elected. On the 24-month imaging, the HAA had enlarged to 6 cm, with disconnection of the 2 stents. A new multilayer stent (9×100 mm) was positioned to "bridge" the gap; however, the proximal part of the new stent did not correctly expand despite multiple attempts to overcome the infolding. The 3 stents became completely thrombosed, but thanks to rich mesenteric collaterals, perfusion of the proper hepatic artery was adequate. The multilayer peripheral stent appears to be an alternative for the treatment of visceral aneurysms in patients with a high surgical risk, but it is not a conventional stent. There are unknowns about its function, behavior, and application. Therefore, more experience is needed to validate the effectiveness of the multilayer stent.