The effect of stent graft oversizing on radial forces considering nitinol wire behavior and vessel characteristics.

Stent graft fixation in the vessel affects the success of endovascular aneurysm repair. Thereby the radial forces of the stent, which are dependent on several factors, play a significant role. In the presented work, a finite element sensitivity study was performed. The radial forces are 29% lower when using the hyperelastic approach for the vessel compared with linear elastic assumptions. Without the linear elastic modeled plaque, the difference increases to 35%. Modeling plaque with linear elastic material approach results in 8% higher forces than with a hyperelastic characteristic. The significant differences resulting from the investigated simplifications of the material lead to the conclusion that it is important to apply an anisotropic nonlinear approach for the vessel. The oversizing study shows that radial forces increase by 64% (0.54 N) when raising the oversize from 10 to 22%, and no further increase in force can be observed beyond these values (vessel diameter D=12 mm). Starting from an oversize of 24%, the radial force steadily decreases. The findings of the investigation show that besides the oversizing the material properties, the ring design and the vessel characteristics have an influence on radial forces.

Real-world performance of the new C3 Gore Excluder stent-graft: 1-year results from the European C3 module of the Global Registry for Endovascular Aortic Treatment (GREAT).

OBJECTIVES: The European C3 module of the Global Registry for Endovascular Aortic Treatment (GREAT) provides "real-world" outcomes for the new C3 Gore Excluder stent-graft, and evaluates the new deployment mechanism. This report presents the 1-year results from 400 patients enrolled in this registry. METHODS: Between August 2010 and December 2012, 400 patients (86.8% male, mean age 73.9 ± 7.8 years) from 13 European sites were enrolled in this registry. Patient demographics, treatment indication, case planning, operative details including repositioning and technical results, and clinical outcome were analyzed. RESULTS: Technical success was achieved in 396/400 (99%) patients. Two patients needed intraoperative open conversion, one for iliac rupture, the second because the stent-graft was pulled down during a cross-over catheterization in an angulated anatomy. Two patients required an unplanned chimney renal stent to treat partial coverage of the left renal artery because of upward displacement of the stent-graft. Graft repositioning occurred in 192/399 (48.1%) patients, most frequently for level readjustment with regard to the renal arteries, and less commonly for contralateral gate reorientation. Final intended position of the stent-graft below the renal arteries was achieved in 96.2% of patients. Thirty-day mortality was two (0.5%) patients. Early reintervention (≤30 days) was required in two (0.5%) patients. Mean follow-up duration was 15.9 ± 8.8 months (range 0-37 months). Late reintervention (>30 days) was required in 26 (6.5%) patients. Estimated freedom from reintervention at 1 year was 95.2% (95% CI 92.3-97%), and at 2 years 91.5% (95% CI 86.8-94.5%). Estimated patient survival at 1 year was 96% (95% CI 93.3-97.6%) and at 2 years 90.6% (95% CI 85.6-93.9%). CONCLUSIONS: Early real-world experience shows that the new C3 delivery system offers advantages in terms of device repositioning resulting in high deployment accuracy. Longer follow-up is required to confirm that this high deployment accuracy results in improved long-term durability.

Stent graft visualization and planning tool for endovascular surgery using finite element analysis.

PURPOSE: A new approach to optimize stent graft selection for endovascular aortic repair is the use of finite element analysis. Once the finite element model is created and solved, a software module is needed to view the simulation results in the clinical work environment. A new tool for interpretation of simulation results, named Medical Postprocessor, that enables comparison of different stent graft configurations and products was designed, implemented and tested. METHODS: Aortic endovascular stent graft ring forces and sealing states in the vessel landing zone of three different configurations were provided in a surgical planning software using the Medical Imaging Interaction Tool Kit (MITK) software system. For data interpretation, software modules for 2D and 3D presentations were implemented. Ten surgeons evaluated the software features of the Medical Postprocessor. These surgeons performed usability tests and answered questionnaires based on their experience with the system. RESULTS: The Medical Postprocessor visualization system enabled vascular surgeons to determine the configuration with the highest overall fixation force in 16+/-6 s, best proximal sealing in 56+/-24s and highest proximal fixation force in 38+/- s. The majority considered the multiformat data provided helpful and found the Medical Postprocessor to be an efficient decision support system for stent graft selection. The evaluation of the user interface results in an ISONORM-conform user interface (113.5 points). CONCLUSION: The Medical Postprocessor visualization software tool for analyzing stent graft properties was evaluated by vascular surgeons. The results show that the software can assist the interpretation of simulation results to optimize stent graft configuration and sizing.

Final results of the prospective European trial of the Endurant stent graft for endovascular abdominal aortic aneurysm repair.

OBJECTIVES: The Endurant Stent Graft System (Medtronic Vascular, Santa Rosa, CA) is specifically designed to treat patients with abdominal aortic aneurysm, including those with difficult anatomies. This is the 1-year report of a prospective, non-randomised, open-label trial at 10 European centres. METHODS: Between November 2007 and August 2008, 80 patients were enrolled for elective endovascular aneurysm repair (EVAR) with the Endurant; 71 with moderate (≤ 60°) and nine with high (60-75°) infrarenal aortic neck angulation. Safety and stent-graft performance were assessed throughout a 1-year follow-up period. RESULTS: The device was successfully delivered and deployed in all cases. All-cause mortality was 5% (4/80), with one possibly device-related death. Serious adverse events were comparable between the high and moderate angulation groups. There were no device migrations, stent fractures, aortic ruptures or conversions to open repair. Maximal aneurysm diameter decreased >5 mm in 42.7% of cases. A total of 28 endoleaks were observed (26 type II, two undetermined). Three secondary endovascular procedures were performed for outflow vessel stenosis, graft limb occlusion and iliac extension, resulting in a secondary patency rate of 100%. No re-interventions were required in the high angulation group. CONCLUSIONS: The Endurant Stent Graft was successfully delivered and deployed in all cases and performed safely and effectively in all patients, including those with unfavourable proximal neck anatomy.

The Anaconda AAA stent graft system: 2-year clinical and technical results of a multicentre clinical evaluation.

INTRODUCTION: This study reports the technical and mid-term clinical results of the second-generation Anaconda AAA Stent Graft System endovascular device for treatment of abdominal aortic aneurysm (AAA). The design of the Anaconda AAA Stent Graft System is characterised by a three-piece system consisting of two proximal independent saddle-shaped nitinol self-expandable rings with hooks fixation, zero body support and vacuum-cleaner tube leg design. METHODS: From July 2002 to April 2005, a total of 61 patients with AAA were enrolled in a multicentre, prospective, non-randomised controlled design study. All patients received a second-generation Anaconda AAA Stent Graft System. They entered a standard follow-up protocol at discharge for 3, 6, 12 and 24 months. Follow-up data included survival; rupture-free survival; incidence of aneurysm rupture, death from aneurysm rupture, aneurysm-related death; freedom from aneurysm expansion; freedom from Types I and III endoleaks; endograft patency and technical and clinical success rates. RESULTS: Successful access to the arterial system was achieved in all patients. The primary technical success was 59 out of 61 and the primary assisted technical success was 60 out of 61. All endovascular grafts were patent without significant twists, kinks or obstructions. Migration was not observed in any of the grafts. During the first 30-day period, two serious adverse events (3%), both not related to the procedure, were observed. Nine patients (15%) needed a secondary intervention; two of these interventions were related to stent graft (3%). The mean aneurysm sac diameter decreased significantly from 57 mm pre-operative to 45mm after 24 months, without aneurysm growth. There was one Type I endoleak at initial implantation, which was corrected using a proximal extension cuff. In total, three Type II endoleaks were still present after 24 months without any signs of aneurysm growth. CONCLUSION: The design features of the second-generation Anaconda AAA Stent Graft System are effective in the treatment of AAAs on mid-term evaluation.

Endurant stent-graft system: preliminary report on an innovative treatment for challenging abdominal aortic aneurysm.

The evolution of stent-grafts and endovascular delivery systems has substantially improved the application rate for and patient outcomes with endovascular aneurysm repair (EVAR) of abdominal aortic aneurysm (AAA), but further development is needed in order to reduce the continuing incidence of complications and secondary re-interventions. Severe angulations at the proximal aneurysm neck and tortuous, calcified, and small iliac arteries are still recognized as important risk factors for successful EVAR of AAA and hence as criteria for exclusion of many potential patients. The Endurant stent-graft is part of a next-generation system that was designed with the clear intention of expanding the applicability of EVAR for AAA while also continuing to improve treatment outcomes and reduce complications. Innovative features of the system design include anchoring pins for ensuring proximal fixation, wire-formed M-shape body stents for improved flexibility and conformability, and a low-profile delivery system with hydrophilic coating that improves trackability and pushability to facilitate the vascular access even in small challenging arteries. Initial clinical experience with the Endurant stent-graft system, including preliminary results from the first-in-human European trial of the device, has demonstrated that the device can be delivered and deployed safely, even in highly angulated anatomies. Technical success was achieved in 90.3% of the patients in the trial. No device-related serious adverse events were seen during the first follow-up period, and no device-related deaths were reported. This new stent-graft will potentially enlarge the patient population suitable for EVAR of AAA.

A single arm, prospective study of an absorbable cyanoacrylate surgical sealant for use in vascular reconstructions as an adjunct to conventional techniques to achieve haemostasis.

AIM: During vascular reconstructive surgery using ePTFE grafts, control of bleeding through suture holes may be time consuming and therefore costly. The ideal sealant has not yet been established. A prospective randomised trial using cyanoacrylate (ETHICON OMNEX Surgical Sealant) showed that the sealant was better than oxidized regenerated cellulose; therefore, a single-arm study to evaluate the performance of a cyanoacrylate surgical sealant in a range of vascular reconstructions was initiated. METHODS: Patients undergoing AV access or vascular reconstruction below the diaphragm were included. The sealant was applied to a dry surgical field following completion of the anastomosis, and then allowed to set for 120 s prior to clamp removal. The primary endpoint was time from clamp release to haemostasis, defined as the absence of any detectable bleeding as determined by the surgeon. Secondary endpoints included the proportion of anastomotic sites achieving haemostasis within 0, 1, 5 and 10 min of post-clamp release, graft type used, frequency of adjunctive measures and number of each type of procedure. Safety endpoints included adverse events from operation until discharge or 48 h. RESULTS: One hundred and ten (110) patients were enrolled at 5 centres; 5 were subsequently excluded from the study. In the remaining 105 patients, there were 157 evaluable anastomotic sites. Mean (SD) and median time to hemostasis by site was 23.2 (77.2) and 0.0 s, respectively. Immediate haemostasis was achieved in 71.3% (112/157) of sites and in 93.6%, 96.8% and 100% within 1, 5 and 10 min, respectively. In the analysis by graft material, haemostasis was immediate in 64.8%, 66.7% and 81.1% of sites in the PTFE, Dacron and autologous groups, respectively. Additional adjunctive measures were required in 3/158 (1.9%) sites in 3 patients. All had initially achieved haemostasis but intra-operative bleeding recurred. There were 12 adverse events, one of which was considered serious but unrelated to the device. CONCLUSION: The time to haemostasis in this study was comparable to that reported in a previous publication. The cyanoacrylate surgical sealant was found to be safe and effective in a variety of vascular reconstruction procedures.

[Current status of vascular surgery]. / Aktueller Stand der Gefässchirurgie.

German vascular surgery compares favourably to international standards. Reconstruction of the complete vascular systems are carried out by experts in specialized centres. Sophisticated techniques are applied to the open and intravascular procedures of small and large vessels. Prosthesis grafts and vein autografts are often used with the help of atraumatic surgical equipment. The external quality control by the German Society of Vascular Surgery and the introduction of continuous medical education in vascular surgery help to maintain this high quality standard. There is a lack of vascular operation, a prerequisite for the development of further independent centres.

[Cardiovascular risk in arterial vascular surgery reconstruction]. / Kardiovaskuläres Risiko bei arteriellen gefässchirurgischen Rekonstruktionen.

Perioperative cardiac complications can limit the outcome after major vascular surgery where the underlying severe coronary artery disease is considered to be the main source. We describe the results of a prospective study including 201 patients undergoing elective vascular surgery. After looking at the encouraging low complication rate (mortality 0.99%, non-fatal myocardial infarction 2.98%, cardiac complications 9.95%) we would recommend the discussed diagnostic strategy. Specialized and expensive cardiac testing should be reserved for a few cases.

[Carotid surgery--reliable and speculative aspects]. / Carotischirurgie--Gesichertes und Spekulatives.

The current status of endarterectomy in carotid artery stenosis is evaluated in prospective randomized studies. The results are very good and high quality. Endovascular therapy is in feasibility studies, and the complication rate is too high compared with the gold standard endarterectomy.

[Ultrasound angiography in diagnosis of deep venous thrombosis and post-thrombotic syndrome. A prospective comparative study]. / Ultraschallangiographie zur Diagnostik der tiefen Beinvenenthrombose und des postthrombotischen Syndroms. Eine prospektive vergleichende Untersuchung.

PURPOSE: Aim of the present study was to establish the value of ultrasound angiography compared with colour duplex sonography and phlebography in the diagnosis of deep venous thrombosis of the leg and insufficiency of the perforating vein. METHOD: Sixty-two patients with deep venous thrombosis of the leg and 30 patients with post-thrombotic syndrome and perforating vein insufficiency underwent diagnostic examination by colour duplex sonography, ultrasound angiography and phlebography. Endoscopic varicose surgery was taken as the gold standard for diagnosis of perforating vein insufficiency. RESULTS: In the diagnosis of deep venous thrombosis, the specificity of colour duplex sonography was 92% in the thigh, 100% in the popliteal area and 89% in the lower leg. Colour angiography showed higher specificity. 95%, in the lower leg. In a diagnosis of perforating vein insufficiency, accuracy specificity of the three procedures was 60% for colour duplex sonography, 47% for phlebography and 80% for ultrasound angiography. CONCLUSIONS: The diagnosis of venous thromboses in the lower leg can be further improved by means of ultrasound angiography. Ultrasound angiography is the best method for demonstrating insufficiency of the perforating vein.

Comparison of tissue plasminogen activator and urokinase in the local infiltration thrombolysis of peripheral arterial occlusions.

Recanalization of the vascular lumen by means of local fibrinolysis is of major importance in the treatment of peripheral arterial occlusive disease. While urokinase and streptokinase have been extensively used for local fibrinolysis, there have been few studies of infiltration thrombolysis with genetically engineered tissue plasminogen activator (rt-PA). The aim of the investigation reported here was to establish whether there is any difference between urokinase and rt-PA in the short- and long-term outcome of local fibrinolytic therapy. One-hundred twenty patients (70 men, 50 women) with acute or subacute femoral (n = 21), femoropopliteal (n = 33), popliteal (n = 13) or popliteocrural (n = 53) thrombotic occlusions were randomized to local lysis using urokinase or rt-PA, and 6 months later follow-up investigations took place. Recanalization of thrombotically occluded vessels, particularly in the lower leg, was found more frequently, and after treatment of shorter duration, with rt-PA. Large local haematomas occurred in 8% of cases in the urokinase group and 15% in the rt-PA group. No serious haemorrhages were encountered in either group. Six months after treatment, the rt-PA group showed lower rates of Fontaine stage III and IV disease and amputation than the urokinase group, with a higher number of patients in Fontaine stage IIb. This study shows that local lysis with rt-PA yields better results than urokinase, not only in the short term but also 6 months later.

[Long-term results after caval filter implantation]. / Langzeitergebnisse nach Cava-Filter-Implantation.

In order to help clarify the long-term results of filter implantation and how best to manage the post-operative care, 92 patients with implanted filters were observed for up to 6 years. The follow-up examinations included detailed interrogation, a clinical investigation, plain abdominal radiography in two planes, contrast-enhanced computed tomography of the vena cava and colour-coded duplex sonography of the vena cava and the veins of the pelvic and legs. In the early phase of the study, two patients who received Günther filters in 1988 experienced dislocation of the filter after 3 months. In the later phase, 85% of those treated with oral anti-coagulants and compression showed patent pelvic veins in areas where, at the time of filter implantation, there had been thrombi with the potential to cause embolism. In 72 cases, the inferior v.cava proved to be patent in the area of the filter.

[Diagnosis of iatrogenic vascular injuries with color-coded duplex ultrasound]. / Diagnostik iatrogener Gefässverletzungen mit der farbkodierten Duplexsonographie.

Between January 1991 and October 1992, 1052 patients who had previously undergone coronarography were examined for iatrogenic lesions around the catheter entry point. Some 3% of them were found to have local complications in the form of haematomas, aneurysms, and arteriovenous fistulas. At the time of investigation 75% of patients with local complications were on oral anticoagulants. In over half of those who had complications on oral anticoagulants there was no alternative to surgical treatment. Colour duplex sonography has the advantage that it can be repeated as often as possible; thus, in cooperation with the cardiac surgeon, the necessity and urgency of surgical intervention in cardiac risk patients can be assessed on an ongoing basis.