Structural implications of fenestrated stent graft misalignment

Preliminary results of the Austrian National Registry regarding the novel iCover bridging stent graft in fenestrated endovascular aortic repair

OBJECTIVE

Bridging stentgrafts (BSGs) are one of the primary limiting factors regarding long-term results after fenestrated endovascular aortic repair (fEVAR). This study aims to report for the first time the outcome of a novel BSG called iCover from a national, multicentric retrospective database.

METHODS

A cohort of 58 patients received 212 BSGs for the renovisceral arteries in fEVAR. Patients were followed-up clinically and with computed-tomography angiography. Study end points were mortality, occurrence of complications, technical success of the BSG implantation, defined as successful deployment with vessel patency and absence of type 1c, 3b, and 3c endoleak, and stability over the follow-up.

RESULTS

Three BSG unrelated mortalities (5.1 %), four BSG unrelated major complications (6.8 %) and five minor complications (8.6 %) occurred. The technical success of iCover was 207/212 (97.6 %), target vessel patency was 100 % over a follow-up of 4.0 months, and no late BSG related endoleak was detected. In two cases, the BSG was dislodged from the balloon and could be parked in a safe position without further sequelae (0.9 %).

CONCLUSION

The iCover represents a feasible BSG for fEVAR with an excellent safety profile and technical success rate in the early phase. Prudent post-dilatation and monitoring of the proximal and distal stent ends can potentially further improve outcome. Longer follow-up series are necessary.

Physician-Modified Stent-Grafts Created in the Three-Dimensionally Aortic Template Have Better Reliability and Greater Alignment With the Target Vessels Than Stent-Grafts Modified Based on Measurements From Computed Tomography

PURPOSE

Physician-modified stent-grafts (PMSG) are widely used, especially when a patient's condition precludes waiting for a custom-made device. In recent years, the modification process has been upgraded using 3-dimensional (3D) aortic templates. Nonetheless, the reliability of PMSG and accuracy of fenestration alignment with the target vessel are not known. Thus, the study is aimed to fulfill the gap in current knowledge.

MATERIALS AND METHODS

Ten computed tomographic (CT) scans of aortic aneurysm previously treated with the fenestrated endovascular repair were selected to 3D-print aortic templates and elastic vessel phantoms. Two vascular surgeons performed fenestrations using the 3D template and modification plan based on CT measurements. Two operators each performed 10 fenestrated stent-grafts in the aortic template and 10 using CT measurements, for a total of 40 fenestrated stent-grafts. Then, stent-grafts were implanted in elastic vessel phantoms, which served to evaluate fenestration alignment with the target vessel. The alignment was judged in a 5-point scale: 0%, 1% to 25%, 26% to 50%, 51% to 75%, and 76% to 100%. The distances between fenestrations served to calculate interobserver variability for both methods. The measurements were processed as interclass correlation coefficient (ICC), Pearson and Spearman correlation, and Bland-Altman plots.

RESULTS

PMSG created with a 3D template had higher interclass correlation coefficient values and Pearson/Spearman correlation than fenestrations created from CT measurements. The rate of fenestration alignment with the target vessel was higher for PMSG created with a 3D template (p=0.007).

CONCLUSIONS

PMSGs created with a 3D template are more reliable and have better fenestration alignment with the target vessel than PMSGs created based on CT measurements.

Systematic Review of the Current In Vitro Experience of the Endovascular Treatment of Juxtarenal Abdominal Aortic Aneurysms by Fenestrated and Parallel Endografting

OBJECTIVE

To identify and analyze the published in vitro benchtop experiments for the assessment of endovascular techniques used for the treatment of juxtarenal abdominal aortic aneurysms (jAAAs).

DATA SOURCES

Scopus, PubMed, and Web of Science.

REVIEW METHODS

A systematic literature search was carried out throughout March 2021 following PRISMA guidelines. Two investigators independently performed title and abstract screening to reveal all benchtop testing evaluating the endovascular treatment of jAAA.

RESULTS

A total of 19 studies were included, 8 evaluating fenestrated (FEVAR) and 11 parallel grafts (PGs). FEVAR studies used different custom testing apparatus (n=7) or 3D-printed models (n=1) to analyze dislodgement and migration resistance, misalignment consequences and causation, and bridging stents' radial force, flareability, fatigue, and fracture resistance. All PG studies used silicone-based models to analyze optimal oversizing, sealing length, gutter behavior, and possible reduction. Test evaluation in FEVAR in vitro testing was based on pullout force analysis (N=5), photo evaluation (n=1), fluoroscopy (n=1), X-rays (n=4), CT analysis (n=3), macro- and microscopic evaluation (n=4), water permeability (n=1), and fatigue simulator testing (n=1), while it was based on CT analysis in all PG studies adding ECG-gate in one study. The most frequently tested devices were Zenit (Cook) (n=7), Endurant (Medtronic) (n=5), and Excluder (Gore) (n=5) as main grafts, and Advanta V12 (n=14) as the bridging device.

CONCLUSIONS

This systematic review presents a broad analysis of the current in vitro methods evaluating the endovascular treatment of jAAA. Fundamental issues have been benchtop tested in both FEVAR and PGs. The analysis of the included studies allowed to recommend an optimal testing design. In vitro testing is a potential tool to further elucidate points of attention hard to investigate in vivo to finally enhance the endovascular treatment outcomes. Future in vitro studies are needed to evaluate the in vitro performance of all indistinctively used devices in the clinical practice.

Abdominal Aortic Aneurysm: Can the Anaconda™ Custom-Made Device Deliver? An International Perspective

Introduction

Since the introduction of endovascular aortic repair (EVAR), it has demonstrated excellent clinical outcomes and has replaced open surgical repair (OSR) in the treatment of abdominal aortic aneurysms (AAA). AAA is a life-threatening abnormal dilation of the abdominal aorta to 1.5 times its normal diameter. Several commercial EVAR devices exist on the global market, with the Terumo Aortic Fenestrated Anaconda™ graft showing superiority. In this study, we sought to provide an international perspective using multicenter-multinational data on the Anaconda™ device characteristics, design, and delivery, and discuss relevant literature.

Materials and Methods

This study represents a cross-sectional international analysis of custom-made fenestrated Anaconda™ device. Ethical and legal approval for data collection was obtained from each of the local authorities. For the statistical analysis, SPSS 28 for Windows and R were utilized. Pearson’s chi-square analysis was used to assess differences in cumulative distribution frequencies between select variables. Statistical significance for all two-tailed tests was set at p < 0.05.

Results

A total of 5,030 Anaconda™ devices were implanted during the 9-year study period in 27 countries spanning 6 continents. The predominant device category was bifurcate (83.6%), whereas the most common proximal ring stent configuration being standard (64.5%). All devices were delivered within 8 weeks of diagnosis, with most being implanted within 6–8 weeks (55.4%). The Anaconda™ was indicated in the 3,891 (77.4%) patients due to competitor rejection/inability to treat unsuitable/complex aortic anatomy. In the remaining 1,139 (22.6%) patients, it was utilized based on surgeon preference. Almost all devices (95%) were delivered along with a prototype. Of the total 5,030 Anaconda™ devices, 438 (8.7%) used 0–1 fenestrations, 2,349 (46.7%) used 2–3, while 2,243 (44.6%) utilized 4, 5, or 6 fenestrations.

Discussion

The Terumo Aortic Fenestrated Anaconda™ device features a highly unique and innovative design that enables it to treat highly complex aortic anatomy while achieving excellent results. The Anaconda™’s custom-made approach allows it to be tailored to individual patient anatomy, in addition to the device prototype provided by Terumo Aortic optimize clinical outcomes. Finally, the fenestrated Anaconda™ is a highly versatile device offering a wide range of device categories, configurations, and sizes.

Systematic Review and Meta-analysis of Physician Modified Endografts for Treatment of Thoraco-Abdominal and Complex Abdominal Aortic Aneurysms

OBJECTIVE

Perform a systematic review and meta-analysis of the outcomes of physician modified endografts (PMEG) for treatment of thoraco-abdominal (TAAA) and complex abdominal aortic aneurysm (C-AAA) repair.

METHODS

We searched MEDLINE, CENTRAL, Web of Science Core Collection, Scielo and Open Grey databases from inception to July 2021 for studies reporting on outcomes of PMEGs for TAAA or C-AAA repair. A systematic review was conducted (protocol CRD42021267856) and data were pooled using a random-effects model of proportions. The outcomes analyzed were major adverse events at 30-days [30-day mortality, myocardial infarction, respiratory failure requiring prolonged ventilation (>24h or re-intubation), renal failure requiring dialysis, bowel ischemia requiring surgery, major stroke or definitive paraplegia]; technical success; 30-day mortality; ruptures; spinal cord ischemia; endoleaks; re-interventions and target vessel patency.

RESULTS

Twenty studies were included. Overall study quality assessment was found to be low. Overall, 909 PMEGs were reported and analyzed. Regarding aneurysm location (n=867), 222 patients had extent I-III TAAAs and 645 had C-AAA or extent IV TAAA. Regarding presentation, 14 studies reported if the patients were treated in an elective or urgent setting (n=782 patients). Overall, 500 (63.9%) patients were treated in an elective setting and 282(36.1%) in an urgent setting. Major adverse events (at thirty-days) occurred in 15.5% of patients (95%CI:10.8;20.8;I²=63%,135/832cases), being 11.6%(95%CI:8.1;15.7;I²=0%,23/280 cases) for elective patients and 24.6% for urgent (95%CI:14.1;36.6;I²=65%,50/192cases). Overall technical success was 97.2%(95%CI:95.4;98.7;I²=0%,587/611cases), being 98.0%(95%CI:92.1;100;I²=0%,106/113cases) for extent I-III TAAAs and 99.4%(95%CI:97.5;100;I²=0%,317/324cases) for C-AAA and extent IV TAAAs. Regarding technique, technical success was 96.1% for FEVAR (95%CI:93.2;98.4;I²=0%,313/329cases) and 99.8% for F/B-EVAR (95%CI:99.8;100;I²=0%,17/18 cases).

CONCLUSION

Physician modified fenestrated or branched grafts for endovascular aortic repair seems feasible and safe in the short-term follow-up. However, the quality of the available data is low which highlights the need for better and more accurate data regarding this technique.

Impact of calcification modeling to improve image fusion accuracy for endovascular aortic aneurysm repair

Since the 1990s, endovascular aortic aneurysm repair (EVAR) has become a common alternative to open surgery for the treatment of abdominal aortic aneurysms (AAAs). To aid the deployment of stent-grafts, fluoroscopic image guidance can be enhanced using preoperative simulation and intraoperative image fusion techniques. However, the impact of calcification (Ca) presence on the guidance accuracy of such techniques is yet to be considered. In the present work, we introduce a guidance tool that accounts for patient-specific Ca presence. Numerical simulations of EVAR were developed for 12 elective AAA patients, both with (With-Ca) and without (No-Ca) Ca consideration. To assess the accuracy of the simulations, the image results were overlaid on corresponding intraoperative images and the overlay error was measured at selected anatomical landmarks. With this approach we gained insight into the impact of Ca presence on image fusion accuracy. Inclusion of Ca improved mean image fusion accuracy by 8.68 ± 4.59%. In addition, a positive correlation between the relative Ca presence and the image fusion accuracy was found (R = .753, p < .005). Our results suggest that considering Ca presence in patient-specific EVAR simulations increases the reliability of EVAR image guidance techniques that utilize numerical simulation, especially for patients with severe aortic Ca presence.

Impact of Insertion Technique and Iliac Artery Anatomy on Fenestrated Endovascular Aneurysm Repair

Purpose: To develop a mechanically realistic aortoiliac model to evaluate anatomic variables associated with stent-graft rotation and to assess common deployment techniques that may contribute to rotation. Materials and Methods: Idealized aortoiliac geometries were constructed either through direct 3-dimensional (3D) printing (rigid) or through casting with polyvinyl alcohol using 3D-printed molds (flexible). Flexible model bending rigidity was controlled by altering wall thickness. Three flexible patient-specific models were also created based on the preoperative computed tomography angiograms. Zenith infrarenal and fenestrated devices were used in this study. The models were pressurized to 100 mm Hg with normal saline. Deployments were performed under fluoroscopy at 37°C. Rotation was calculated by tracking the change in position of gold markers affixed to the devices. Results: In the rigid idealized models, stent-graft rotation increased with increasing torsion; torsion levels of 1.6, 2.6, and 3.6 mm−1 had mean rotations of 5.2°±0.03°, 11.2°±4.8°, and 27.6°±13.0°, respectively (p<0.001). In the flexible models, the highest rotation (58°±3.0°) was observed in models with high torsion and high rigidity (7.5 mm−1 net torsion and 254 N·m2 flexural rigidity). No rotation was observed in the absence of torsion. Applying torque to the device during insertion significantly increased stent-graft rotation by an average of 28° across all levels of torsion (p<0.01). Multiple device insertions prior to deployment did not change the observed device rotation. The patient-specific models accurately predicted the degree of rotation seen intraoperatively to within 5°. Conclusion: Insertion technique plays an important role in the degree of stent-graft rotation during deployment. Our model suggests that in vivo correction of device orientation can increase the observed rotation and supports the concept of fully removing the device, adjusting the orientation, and subsequently reinserting. Additionally, increasing iliac artery torsion in the presence of increased vessel rigidity results in stent-graft rotation.

In Vitro Evaluation of the Gore Viabahn Balloon-Expandable Stent-Graft for Fenestrated Endovascular Aortic Repair

Purpose: To evaluate the safety and integrity of a new stent-graft as a potential bridging device in fenestrated stent-grafts using an in vitro fenestrated model. Materials and Methods: Polyester test sheets with ten 6-mm- or 8-mm-diameter fenestrations were used to simulate a fenestrated main body endoprosthesis. In total, 50 Viabahn balloon-expandable (VBX) stent-grafts of varying lengths (29 and 39 mm) and diameters (6, 7, and 8 mm) were implanted in the fitting fenestrations. After release, the 6- and 7-mm-diameter stent-grafts were flared with a 10×20-mm angioplasty balloon; a 12×20-mm balloon was used in the 8-mm-diameter devices. Safety of the devices was defined as absence of fractures detected on radiography or computed tomography (CT), as well as material failure detected by microscopy and water permeability testing. The forces (in Newtons, N) needed for perpendicular dislocation (pullout force) and axial dislocation (shear stress force) were also evaluated. Results: Forty VBX stent-grafts were subjected to digital radiographic imaging and multiplanar CT. None showed any stent fracture. Subsequent microscopy indicated no damage to the fabric or separation of the graft after flaring. Ten VBX stent-grafts underwent water permeability testing after flaring; no water passed through the graft wall during a 10-minute period under an intraluminal pressure at 120 mm Hg. Testing of 25 VBX stent-grafts revealed initial pullout forces between 11.3 and 31 N. Shear stress tests showed that the average force needed to dislocate the stent-grafts by 50% of their diameter ranged between 5.75 and 6.91 N (mean 6.1±0.5 N) for the 6-mm stents and between 3.31 and 5.4 N (mean 4.4±0.8) for the 8-mm stents. Conclusion: This preliminary study demonstrated the applicability of the VBX as a bridging stent-graft in a simulated fenestration model. A comparison with other stent-grafts and clinical assessment are required.