Mechanical Comparison between Fenestrated Endograft and Physician-Made Fenestrations.

INTRODUCTION: A fenestrated endograft (FE) is the first-line endovascular option for juxta and pararenal abdominal aortic aneurysms. A physician-modified stent-graft (PMSG) and laser in situ fenestration (LISF) have emerged to circumvent manufacturing delays, anatomic standards, and the procedure's cost raised by FE. The objective was to compare different fenestrations from a mechanical point of view. METHODS: In total, five Zenith Cook fenestrations (Cook Medical, Bloomington, IN, USA) and five Anaconda fenestrations (Terumo Company, Inchinnan, Scotland, UK) were included in this study. Laser ISF and PMSG were created on a Cook TX2 polyethylene terephthalate (PET) cover material (Cook Medical, Bloomington, IN, USA). In total, five LISFs and fifty-five PMSG were created. All fenestrations included reached an 8 mm diameter. Radial extension tests were then performed to identify differences in the mechanical behavior between the fenestration designs. The branch pull-out force was measured to test the stability of assembling with a calibrated 8 mm branch. Fatigue tests were performed on the devices to assess the long-term outcomes of the endograft with an oversized 9 mm branch. RESULTS: The results revealed that at over 2 mm of oversizing, the highest average radial strength was 33.4 ± 6.9 N for the Zenith Cook fenestration. The radial strength was higher with the custom-made fenestrations, including both Zenith Cook and Anaconda fenestrations (9.5 ± 4.7 N and 4.49 ± 0.28 N). The comparison between LISF and double loop PMSG highlighted a higher strength value compared with LISF (3.96 N ± 1.86 vs. 2.7 N ± 0.82; p= 0.018). The diameter of the fenestrations varied between 8 and 9 mm. As the pin caliber inserted in the fenestration was 9 mm, one could consider that all fenestrations underwent an "elastic recoil" after cycling. The largest elastic recoil was observed in the non-reinforced/OC fenestrations (40%). A 10% elastic recoil was observed with LISF. CONCLUSION: In terms of mechanical behavior, the custom-made fenestration produced the highest results in terms of radial and branch pull-out strength. Both PMSG and LISF could be improved with the standardization of the fenestration creation protocol.

Mechanical Performance Assessment of Physician Modified Aortic Stent Graft.

OBJECTIVE: This study aimed to compare various fenestration configurations of physician modified aortic stent grafts in order to identify which design parameters have a significant influence on the mechanical behaviour of the fenestration. METHODS: the fenestration configurations were considered according to different manufacturing parameters: cutting technique, fenestration reinforcement, suture material, reinforcement loop design, and number of suture points. The performance of the graft/bridging stent assembly was assessed at various levels: (1) branch pull out force; (2) fenestration enlargement and rupture strength; (3) balloon angioplasty resistance; and (4) behaviour under cyclic fatigue. RESULTS: Sixty manual fenestrations were created. The tests performed on the fenestrations had several main findings. First, reinforcement increased the radial force on the branch, which increased the pull out force; this may limit migration of the bridging stent in vivo. The phenomenon was amplified with a snare reinforced fenestration, which seemed to be the most efficient. Moreover, increasing the number of suture passes also appeared to increase the branch extraction force securing the assembly. The enlargement tests showed that non-reinforced fenestrations had the weakest radial strength. This was confirmed with the balloon angioplasty test, which showed that these latter specimens undergo the most significant textile degradation. After fatigue tests, all fenestrations were larger, showing that elastic recoil was incomplete in all samples. The largest recoil was observed in the non-reinforced ophthalmological cautery (OC) fenestrations (40%). Regarding the behaviour of the samples up to rupture, all samples behaved in a similar way; however, the double loop fenestration strength level was the highest. CONCLUSION: This study demonstrated that the snare double loop reinforcement has an advantage regarding durability of the graft branch assembly. Moreover, non-reinforced fenestrations show signs of weakness and lack of stability, which questions the in situ or laser fenestration procedures.

Conversion From an Outpatient to an Inpatient Setting After an Endovascular Treatment for Lower Extremity Artery Disease.

BACKGROUND: Outpatient endovascular treatment (EVT) for lower extremity artery disease (LEAD) is increasing. Some patients will, nonetheless, unexpectedly stay hospitalized for the night after the procedure. The purpose of this study was to identify the factors associated with a conversion from an outpatient setting (OS) to an inpatient setting (IS). METHODS: From April 2017 to August 2019, we performed 745 EVT for LEAD. Patients scheduled for a same-day discharge procedure were retrospectively analyzed. The factors potentially associated with a conversion to an IS were assessed. Results are expressed as odds ratio (OR) with 95% confidence intervals. RESULTS: Among the 198 (26.6%) patients scheduled for outpatient EVT, mean age was 70.8±14.1 years old, 34.3% had an ASA score≥3 and 38.4% presented a chronic limb-threatening ischemia. Twenty-eight patients (14.1%) were converted from an OS to IS. Univariate analysis found that Rutherford stage≥4 (OR = 5.09 [2.11-12.27], P < 0.001), high blood pressure (OR = 3.19 [1.06-9.63], P = 0.040), ASA score≥3 (OR = 3.61 [1.58-8.24], P = 0.002), duration of procedure ≥90 min (OR = 2.36, [1.03-5.39], P = 0.042), anterograde puncture (OR = 2.94, [1.30-6.66], P = 0.009), arrival in the operating room ≥12:00 (OR = 13.05, [5.29-32.17], P < 0.001) and general anesthesia (OR = 3.89, [1.20-12.62], P = 0.024) were associated with a conversion. The multivariate analysis revealed that an arrival in the operative room ≥12:00 (OR = 11.71, [3.85-35.60], P < 0.001) and general anesthesia (OR = 6.76, [1.28-35.82], P = 0.009) were independent factors associated with a conversion. CONCLUSION: Arrival in the operative room after 12:00 and general anesthesia represent two independent correctible factors associated with the risk of OS failure. No factor directly related to comorbidities or the LEAD severity was identified.

Degradation Phenomena on "Homemade" Explanted Aortic Textile Endografts.

OBJECTIVE: In the 1990s, the concept of "homemade" endografts (EGs) using commercially available materials was proposed in clinical practice for endovascular abdominal aortic repair (EVAR). The aim of this study was to analyse the ageing phenomena of these EGs in light of explant analyses. METHODS: The study focused on five explanted homemade EGs collected from 2012 to 2014. The explants were assessed in accordance with the ISO 9001/13485 certified standard protocol, which included naked eye evaluation, organic remnant cleaning, and microscopic and endoscopic examinations and analysis (magnification range from 20% to 200%). The observations report followed a classification based on 12 features assessing the fabric cover, the stitch filament, and the stents. RESULTS: The reasons for explantation were type 1 endoleak in three cases and aneurysm sac growth in two. The implantation duration ranged from 56 to 202 months. Sixty three per cent of the fabric surface lesions (holes and tears) were related to abrasion between the fabric and the stents. Up to 33% of the knots used to connect adjacent stents were broken on one EG. Other defects including running suture rupture and stent corrosion were also observed. The overall hole cumulated surface ranged from 0.377 mm2 (56 month of implantation) up to 3.21 mm2 (78 month of implantation). CONCLUSION: In this study, various ageing phenomena on homemade textile EGs were identified and classified. The main damaging mechanisms were related to abrasion stress leading to tears and holes in the fabric, stitch ruptures, and detachment of stent segments responsible for serious EG deformations and further degradation.

Mechanical Behaviour of Fenestrations in Current Aortic Endografts.

OBJECTIVE: The aim of this study was to assess the mechanical characteristics of current commercially available fenestrated endografts (FE). The performance of the fenestrations according to the design were compared as the relationship between a bridging covered stent graft (CSG) and the fenestration. METHODS: A total of 21 Zenith (Cook Medical, Bloomington, IN, USA) and 17 Anaconda (Terumo Company, Inchinnan, UK) fenestrations were studied. Radial extension tests were performed, inserting two half cylinders spaced up to 2 mm in a 7 mm diameter fenestration from each device. Branch pull out force was measured to test the stability of the assembly with a calibrated 8 mm branch and two CSGs: Advanta V12 (Atrium Medical; Hudson, NH, USA) and BeGraft Peripheral Stent Graft (Bentley InnoMed GmbH, Hechingen, Germany). A branch was inserted in both the 7 mm diameter fenestrations and in a control 7 mm fenestration. Fatigue tests were performed on the devices to assess long term outcomes of the endograft. RESULTS: Over a 2 mm vertical displacement, the resulting loading curves look similar for both devices. The force value level was 33.4 ± 6.9 N for the Cook fenestration and 54.45 ± 18 N for the Anaconda fenestration (p = .001). With respect to an 8 mm calibrated branch, the required extraction strength from the fenestration was statistically significantly greater with the Anaconda device (9.5 ± 4.7 N vs. 4.49 ± 0.28 N; p = .001). The required strength to extract the V12 CSG from a control cylindered shape was statistically significantly higher than for the BeGraft CSG (6.75 ± 2.86 N vs. 1.83 ± 0.67 N; p = .003). The surface area of the fenestration of the Cook device was increased with cycling (7 200 cycles) compared with the Anaconda device (15.5% vs. 6.5% hole surface area increase). CONCLUSION: The mechanical performance of the fenestration can be fine tuned by considering its design. A CSG optimising the performance of the fenestration and the CGS-fenestration interface could reduce the risk of leakage in clinical practice.

Comprehensive Review of Physician Modified Aortic Stent Grafts: Technical and Clinical Outcomes.

OBJECTIVE: Physician modified stent grafts (PMSGs) present satisfactory results in selected cases of complex aortic pathologies. However, the technique lacks standardisation and depends on the surgeon and aortic segment. The aim of this article is to review comprehensively the technical details and clinical results of PMSGs related to patients with pathology in all aortic locations. METHODS: A MEDLINE search (last search 20 April 2020) identified 20 relevant papers in the English language published over the last 20 years evaluating clinical outcomes after a PMSG and specifying the technical details to design it. RESULTS: Seven hundred and eleven patients were included in the analyses, with 59% being operated on as an emergency. Ninety-two per cent of abdominal aortic segment PMSGs (A-PMSGs) were performed either as an emergency or before 2012. The main indications were available in 670 cases; 435 were degenerative aneurysms (64.9%) and 171 were aortic dissections (25.5%). Most of the endografts used were composed of polyethylene terephthalate, except for the Ankura (expanded polytetrafluoroethylene [Lifetech Scientific, Shenzhen, China]; n = 50, 7.5%). The Valiant (Medtronic, Minneapolis, MN, USA) represented 65% (n = 169) of aortic arch PMSGs (aa-PMSGs) and the Zenith platform (Cook Medical, Bloomington, IN, USA) 51% (n = 139) of A-PMSGs. A snare was used to reinforce the fenestration in 458 PMSGs (66%) and a cautery device cut the fenestration in 484 (75%) PMSGs. No bridging stent was used in 47 (7.0%) PMSGs (these aa-PMSGs had large fenestrations). Technical success ranged from 87.5% to 100% and 30 day mortality from 0% to 8%. Primary branch patency ranged from 96.3% to 100% at 12 month follow up. Zero to 14% of patients experienced type 3 or type 1 endoleak at 14.8 month follow up. CONCLUSION: PMSG is a useful technique, particularly when validated treatments are not available. However, it is a non-standardised technique and the long term consequences of modifications remain unknown.