Evaluation of Electrocardiogram-Gated Computed Tomography Angiography to Quantify Changes in Geometry and Dynamic Behavior during the Cardiac Cycle of the Nellix Endovascular Sealing System.

Background: The Nellix endovascular sealing system (EVAS) was a unique concept with regard to its sealing concept that failed, related to high migration rates. We investigated the changes in aortoiliac morphology during the cardiac cycle before and after EVAS using electrocardiography (ECG)-gated CT. Methods: Eight patients scheduled for EVAS were prospectively enrolled. ECG-gated CT scans were made pre- and postoperatively. Measurements were performed in the mid-systolic and mid-diastolic phases. Endpoints were changes in infrarenal aortoiliac morphology postoperatively compared to preoperatively and their changes in the cardiac cycle. Results: Both pre- and postoperatively, there were no changes during the cardiac cycle. EVAS caused an increase in neck diameter and surface in both phases (p < 0.001). EVAS increased the luminal AAA volume (p < 0.001), with a decrease in thrombus volume (p < 0.001) in both phases and an increase in total volume (p < 0.001) in the systolic phase. During follow-up, one patient presented with >5 mm migration. There were no differences in the movements of this patient compared to the remaining patients. Conclusion: The cardiac cycle had a very limited effect on the aortoiliac dynamics before and after EVAS and, therefore, there is probably not a role for ECG-gated CT in enhanced surveillance programs. EVAS itself has a significant impact on anatomy, particularly the neck diameter, length, and volumes of the AAA.

Physiological Appearance of Hybrid FDG-Positron Emission Tomography/Computed Tomography Imaging Following Uncomplicated Endovascular Aneurysm Sealing Using the Nellix Endoprosthesis.

Purpose: To investigate the physiological uptake of hybrid fluorine-18-fluorodeoxyglucose (FDG)-positron emission tomography/computed tomography (PET/CT) before and after an uncomplicated endovascular aneurysm sealing (EVAS) procedure as a possible tool to diagnose EVAS graft infection and differentiate from postimplantation syndrome. Materials and Methods: Eight consecutive male patients (median age 78 years) scheduled for elective EVAS were included in the prospective study (ClinicalTrials.gov identifier NCT02349100). FDG-PET/CT scans were performed in all patients before the procedure and 6 weeks after EVAS. The abdominal aorta was analyzed in 4 regions: suprarenal, infrarenal neck, aneurysm sac, and iliac. The following parameters were obtained for each region: standard uptake value (SUV), tissue to background ratio (TBR), and visual examination of FDG uptake to ascertain its distribution. Demographic data were obtained from medical files and scored based on reporting standards. Results: Visual examination showed no difference between pre- and postprocedure FDG uptake, which was homogenous. In the suprarenal region no significant pre- and postprocedure differences were observed for the SUV and TBR parameters. The infrarenal neck region showed a significant decrease in the SUV and no significant decrease in the TBR. The aneurysm sac and iliac regions both showed a significant decrease in SUV and TBR between the pre- and postprocedure scans. Conclusion: Physiological FDG uptake after EVAS was stable or decreased with regard to the preprocedure measurements. Future research is needed to assess the applicability and cutoff values of FDG-PET/CT scanning to detect endograft infection after EVAS.

Evolution of Computed Tomography Imaging the First Year after Endovascular Sealing of Infrarenal Aortic Aneurysms Using the Nellix Device.

BACKGROUND: The Nellix endovascular aneurysm sealing (EVAS) system is an alternative endovascular treatment option for infrarenal aortic aneurysms (AAAs), with a unique appearance on computed tomography angiography (CTA). Normal evolution of post-EVAS CTA appearance follow-up is still largely unknown and important to timely detect eventual complications. The objective is to assess the normal appearance of CTA images 30 days and 1 year after EVAS in 50 consecutive patients. METHODS: Fifty patients treated with Nellix EVAS for an infrarenal AAA were included from 3 hospitals. Using dedicated software, a total of 150 CTA scans were analyzed by predetermined variables per anatomical segment. RESULTS: Thirty days post-EVAS, there was a slight, but not statistically significant, increase in AAA diameter that returned to the preoperative value after 1 year. A shift in total aortic volume distribution was observed without changing aortic diameter, including a trend toward a decreased thrombus volume (85.6 ± 49.1 mL and 78.8 ± 35.5 mL at 30 days and 1 year, respectively, P < 0.242) and a slight, but statistically significant, increase in polymer volume (68.2 ± 34.1 mL and 71.9 ± 35.2 mL at 30 days and 1 year, respectively, P < 0.001). The ß-angle (P = 0.06) and iliac artery angulation (P < 0.001) decreased after implant. The latter returned to its original state after 1 year, whereas the neck straightening remained. Over time, there was a significant decrease in radiodensity in the middle of the polymer-filled endobags with an increase at its edges (P < 0.05). Thrombus radiodensity significantly increased over the first year (P < 0.05). Diameters of the infrarenal neck and common iliac arteries remained unchanged, no endoleaks were observed, and the position of the device was stable. CONCLUSIONS: Change of CT appearance after EVAS is unique, and as such, the judgment of these images requires experience. The appearance of the endobags in respect to volume and radiodensity differ from classic EVAR. Normal changes over time are observed in aortoiliac angulation, volumes, and radiodensities.

Editor's Choice - Occurrence and Classification of Proximal Type I Endoleaks After EndoVascular Aneurysm Sealing Using the Nellix™ Device.

OBJECTIVE/BACKGROUND: Proximal type I endoleaks are associated with abdominal aortic aneurysm (AAA) growth and rupture and necessitate repair. The Nellix™ EndoVascular Aneurysm Sealing (EVAS) system is a unique approach to AAA repair, where the appearance and treatment of endoleaks is also different. This study aimed to analyse and categorise proximal endoleaks in an EVAS treated cohort. METHODS: All patients, treated from February 2013 to December 2015, in 15 experienced EVAS centres, presenting with proximal endoleak were included. Computed tomography scans were analysed by a core laboratory. A consensus meeting was organised to discuss and qualify each case for selection, technical aspects, and possible causes of the endoleak. Endoleaks were classified using a novel classification system for EVAS. RESULTS: During the study period 1851 patients were treated using EVAS at 15 centres and followed for a median of 494 ± 283 days. Among these, 58 cases (3.1%) developed a proximal endoleak (1.5% early and 1.7% late); of these, 84% of 58 patients were treated outside the original and 96% outside the current, refined, instructions for use. Low stent positioning was the most likely cause in 44.6%, a hostile anatomy in 16.1%, and a combination of both in 33.9%. Treatment, by embolisation or proximal extension, was performed in 47% of cases, with a technical success of 97%. CONCLUSION: The overall incidence of proximal endoleak after EVAS is 3.1% after a mean follow-up period of 16 months, with 1.5% occurring within 30 days. Their occurrence is related to patient selection and stent positioning. Early detection and classification is crucial to avoid the potential of sac rupture.

Validation of pre-procedural aortic aneurysm volume calculations to estimate procedural fill volume of endobags in endovascular aortic sealing.

BACKGROUND: Endovascular aortic sealing (EVAS) with a sac anchoring endoprosthesis excludes abdominal aortic aneurysms based on polymer filling of endobags. Primary objective was to assess the reliability of pre-procedural computed tomography (CT) scans based calculations of required endobag volume in relation to intraoperative volume of the endobags. METHODS: Forty elective EVAS patients were included. Pre-procedural estimations of endobag volume were based on CT segmentations of aortic flow lumen volume, including both automated and manually-adjusted segmentations, performed by two experienced users. Additionally, changes in maximum AAA diameter, thrombus volume and total AAA volume were calculated from pre- and post-procedural CT scans. RESULTS: Automatically determined volumes were comparable to manually-adjusted calculations (75.3 vs. 75.7 mL) and inter-observer agreement regarding pre-EVAS calculations of prefill volume appeared almost perfect with an intra-class correlation coefficient of 0.98 (95% CI: 0.96-0.99). The mean pressure of the endobags was 185 mmHg. Manually-adjusted pre-procedural volume calculations underestimated procedural volume of the endobags (-11.3±9.9 mL). Differences between pre-EVAS and procedural volume measurements were independent from endobag pressure (r=-0.06, P=0.72), prepocedural thrombus volume (r=-0.303, P=0.057) and changes in total AAA volume (r=0.02, P=0.91). A significant association was determined between differences in pre-EVAS and endobag volume versus changes in thrombus volume pre- and post-procedural (r=0.39, P=0.01). CONCLUSIONS: In this validation study, pre-procedural volume measurements underestimate the actual fill volume of the endobags. It should be advised to perform a prefill of the endobags during the EVAS procedure.

The Nellix™ EndoVascular sealing system in patients with abdominal aortic aneurysms in conjunction with iliac artery occlusive disease.

Introduction Concomitant abdominal aortic aneurysm formation and aortoiliac occlusive disease is a challenging combination, often requiring open reconstructive surgery. In this study, we have assessed a single center experience of the Nellix EndoVascular Aneurysm Sealing System in the treatment of an abdominal aortic aneurysm in conjunction with iliac artery occlusive disease. Methods Retrospectively case files of patients treated with Nellix EndoVascular Aneurysm Sealing System in a single center were reviewed. The primary endpoints of the study were the technical success of Nellix EndoVascular Aneurysm Sealing System in patients with coincidental iliac artery occlusive disease and the successful exclusion of the aneurysm during follow-up. Results Of the 96 patients that were treated with Nellix EndoVascular Aneurysm Sealing System, five were identified that had an abdominal aortic aneurysm in conjunction with iliac artery occlusive disease. Treated patients had either unilateral (n = 4) or bilateral (n = 1) common iliac artery occlusive disease varying from 70% stenosis to complete occlusions. The lesion length varied from 5 to 50 mm and in two cases it involved an occluded bare metal stent. The indication for surgery was the abdominal aortic aneurysm in all patients, including three also suffering from claudication. In all patients the iliac artery occlusive disease was pretreated with balloon-expandable covered stents. Technical success was achieved in all five patients. After a median follow-up of nine months all stents were patent with no signs of endoleak and stable aneurysm diameters. All patients were free of intermittent claudication or ischemic wounds. Conclusion Nellix EndoVascular Aneurysm Sealing System seems feasible and safe in patients with a combination of abdominal aortic aneurysm and iliac artery occlusive disease.

Imaging After Nellix Endovascular Aneurysm Sealing: A Consensus Document.

Endovascular aneurysm sealing (EVAS) using the Nellix system is a new and different method of abdominal aortic aneurysm repair. Normal postoperative imaging has unique appearances that change with time; complications also have different and specific appearances. This consensus document on the imaging findings after Nellix EVAS is based on the collective experience of the sites involved in the Nellix EVAS Global Forward Registry and the US Investigational Device Exemption Trial. The normal findings on computed tomography (CT), duplex ultrasound, magnetic resonance imaging, and plain radiography are described. With time, endobag appearances change on CT due to contrast migration to the margins of the hydrogel polymer within the endobag. Air within the endobag also has unique appearances that change over time. Among the complications after Nellix EVAS, type I endoleak usually presents as a curvilinear area of flow between the endobag and aortic wall, while type II endoleak is typically small and usually occurs where an aortic branch artery lies adjacent to an irregular aortic blood lumen that is not completely filled by the endobag. Procedural aortic injury is an uncommon but important complication that occurs as a result of overfilling of the endobags during Nellix EVAS. The optimum imaging surveillance algorithm after Nellix EVAS has yet to be defined but is largely CT-based, especially in the first year postprocedure. However, duplex ultrasound also appears to be a sensitive modality in identifying normal appearances and complications.

Treatment of Type IIIb Endoleaks After EVAR Using the Nellix EndoVascular Aneurysm Sealing System.

PURPOSE: To describe the successful endovascular treatment of 2 patients with type IIIb endoleak using the Nellix EndoVascular Aneurysm Sealing (EVAS) System. CASE REPORT: Two men aged 75 and 83 years presented with type IIIb endoleak several years (8 and 3, respectively) after initial endovascular aneurysm repair. Dual Nellix endoprosthesis were deployed in the stent-grafts, and the endobags were filled with polymer to seal the defect and eliminate the endoleak. The perioperative periods were uneventful. At up to 6-month follow-up, no endoleaks were detected, aneurysm diameters were unchanged, and the endografts were patent. One patient died 7 months after revision due to a metastatic malignancy. CONCLUSION: The Nellix EVAS System may prove useful for the treatment of type IIIb endoleak.

EndoAnchors to Resolve Persistent Type Ia Endoleak Secondary to Proximal Cuff With Parallel Graft Placement.

PURPOSE: To describe 2 patients with a distally migrated endograft causing a type Ia endoleak and treatment with a proximal cuff and chimney grafts that required EndoAnchors to finally seal the leak. CASE REPORT: Two men, ages 86 and 72 years, presented with stent-graft migration and type Ia endoleak at 5 and 15 years after endovascular repair, respectively. Both were treated with a proximal cuff in combination with a chimney graft to the left renal artery. In both cases, the type Ia endoleak persisted, likely due to gutter formation. Both patients were treated in the same setting with EndoAnchors that instantly resolved the endoleak. At 1-year follow-up, there was no recurrent endoleak or migration, with patent chimney grafts and renal arteries and stable renal function. CONCLUSION: EndoAnchors may effectively resolve a persistent type Ia endoleak arising from gutter formation after placement of a proximal cuff and chimney grafts.

Common Iliac Artery Aneurysm Repair Using a Sac-Anchoring Endograft to Preserve the Internal Iliac Artery.

PURPOSE: To report the application of the Nellix endovascular aneurysm sealing system to successfully treat a unilateral common iliac aneurysm and preserve the internal iliac artery. CASE REPORT: An 85-year-old man presented with right-sided necrosis of the third and fourth toe. Computed tomography angiography (CTA) showed a right 40-mm popliteal aneurysm and a 38-mm left fusiform common iliac artery aneurysm. After endovascular exclusion of the popliteal aneurysm, the Nellix device was positioned to exclude the common iliac artery aneurysm while preserving the internal iliac artery. Postoperative CTA showed no endoleak and a patent internal iliac artery. At 1 year, duplex ultrasound documented a common iliac aneurysm diameter of 32 mm without complications. CONCLUSION: Endovascular sealing using the Nellix device can be applied to exclude selected common iliac artery aneurysms with an adequate length and a minimal distal neck, with preservation of the internal iliac artery. The endobag can be positioned such that the aneurysm is completely excluded while the orifice of the side branch is not endangered.

Late Conversion After Sac Anchoring Endoprosthesis for Secondary Aortic Aneurysm Infection.

PURPOSE: To demonstrate explantation of the Nellix Endovascular Aneurysm Sealing (EVAS) System in the setting of infection. CASE REPORTS: Two male patients, 71 and 83 years old, underwent Nellix implantation for asymptomatic infrarenal aortic aneurysms measuring 5.1 and 6.3 cm, respectively. Each developed late infections at 8 and 4 months post EVAS, respectively. The first patient experienced aneurysm rupture after medical therapy failed; the Nellix endosystem was explanted in an uneventful procedure. The second patient developed an aortoduodenal fistula, which was sutured before the Nellix device was removed without complications. The patient died 3 months later, presumably due to ongoing infection. CONCLUSION: The need to explant a Nellix EVAS System due to graft infection is a straightforward procedure compared to the removal of a conventional endograft with suprarenal fixation. It requires only temporary suprarenal clamping. The devices can be easily removed due to the lack of penetrating components and without damage to the aortic segment needed to create an anastomosis.

Abdominal Aortic Aneurysm Repair Using Nellix™ EndoVascular Aneurysm Sealing.

Since the dawn of endovascular aortic aneurysm repair (EVAR), starting from its initial report in 1991, there has been a significant evolution in stent graft design and delivery systems. Complications, mostly endoleaks, and re-intervention rates after EVAR remain amongst the most challenging aspects in comparison with traditional open repair. The use of a sac-anchoring endograft changes the approach of aneurysm exclusion. The Nellix™ EndoVascular Aneurysm Sealing system (Endologix Inc., Irvine, CA) consists of balloon expandable stents surrounded by endobags that are filled with a polymer thereby sealing the aneurysm. By sealing the aneurysm sac instead of exclusion with only proximal and distal fixation, the risk of stent migration and endoleaks is theoretically diminished. Current investigational use is aimed to confirm clinical success, decreased complication, and secondary intervention rates compared to conventional endovascular repair.