Geometrical Changes of the Aorta as Predictors for Thromboembolic Events After EVAR With the Anaconda Stent-Graft

Vascular Flow Phantom of A Cohort-Based Averaged Abdominal Aortic Aneurysm: Design, Fabrication and Characterization

PURPOSE

Vascular flow phantoms are an invaluable tool for in vitro and in silico studies, but their design and fabrication processes are often not reported. In this study, a framework is introduced to design and fabricate 3D printable high-fidelity cohort-based averaged abdominal aortic aneurysm (AAA) phantoms.

METHODS

AAA geometries of 50 patients were segmented from preoperative computed tomography angiography scans. The segmented geometries and center lumen lines (CLL) were used in an in-house developed algorithm to average the CLL coordinates and corresponding diameters over the entire cohort. The reconstructed averaged anatomy was 3D printed as a thin-walled flow phantom with Formlabs Flexible 80A resin. The acoustic properties of the resin were characterized and the feasibility of flow field quantification inside the phantom with ultrasound particle imaging velocimetry (echoPIV) was investigated.

RESULTS

Comparison between patient-specific models generated by our method and their corresponding reference segmentations, for ten patients, showed a mean Sørensen-Dice similarity coefficient of 0.916 ± 0.21 and the largest distances (5-10% of the lumen diameter) were found at the aneurysmal sac. The Flexible 80A resin had an average speed of sound of 1785 m/s, attenuation of 7.8 dB/mm and density of 1130 kg/m3. Volumetric flow profiles obtained with echoPIV in the suprarenal artery (i.e. phantom inlet) matched the flow sensor data.

CONCLUSION

The reported framework was used to make an averaged, cohort-based AAA model, which showed a good match with its reference model. A 3D printed, thin-walled phantom was made based on this model and the feasibility of flow field quantification inside the phantom was shown.

Impact of Antithrombotic Therapy on Thrombotic and Bleeding Complications after Elective Endovascular Repair of Abdominal Aortic Aneurysms

PURPOSE

To investigate the influence of antithrombotic therapy on occurrence of thrombotic and bleeding complications after endovascular aneurysm repair (EVAR).

METHODS

In this retrospective single-center cohort study, patients who underwent elective endovascular aneurysm repair for abdominal aortic aneurysm were categorized into three antithrombotic groups: single antiplatelet therapy (SAPT), anticoagulants, or dual antiplatelet therapy (DAPT). Outcome measures were the incidence of major adverse cardiovascular events (MACE), prosthetic limb occlusions, and bleeding complications during follow-up.

RESULTS

Among 616 patients (SAPT: n = 450, anticoagulants: n = 84, and DAPT: n = 82), Kaplan-Meier analysis showed no significant difference (log-rank p = 0.37) in incidence of MACE between patients receiving SAPT (20.9%), anticoagulants (25.0%), and DAPT (14.6%) during a median follow-up of almost 4 years. In multivariable Cox regression analysis, only age (HR = 1.03; 95% CI 1.01-1.06, p = 0.01) and American Society of Anesthesiologists (ASA) classification (HR = 1.46; 95% CI 1.12-1.91; p = 0.01) were significant predictors for MACE. Prosthetic limb occlusion was observed in 38 patients during a median follow-up of 4 years; incidence between patients receiving SAPT (5.8%), anticoagulants (10.7%), and DAPT (3.7%) was not significantly different (log-rank p = 0.08). Age (HR = 0.96; 95% CI 0.92-1.00; p = 0.03) and use of anticoagulants (HR = 3.79, 95% CI 1.46-9.83; p < 0.01) were significant predictors for prosthetic limb occlusion. Bleeding complications occurred in 73 patients during median follow-up of almost 4 years, without significant difference (log rank p = 0.06) in incidence between patients receiving SAPT (10.7%), anticoagulants (19.0%), and DAPT (11.0%). ASA classification (HR = 1.74; 95% CI 1.23-2.46; p < 0.01) was a significant predictor for bleeding complications.

CONCLUSION

Use of anticoagulants after EVAR appears to be associated with a higher risk of prosthetic limb occlusion compared to the use of single or dual antiplatelet therapy.

Fenestrated Endovascular Aortic Repair of Complex Aneurysm Using the Anaconda Fenestrated Device: 1-Year Results From the French Multicenter Registry

PURPOSE

This study aims to assess the safety and efficacy of the fenestrated Anaconda device for the treatment of complex aortic aneurysms over 1 year in daily clinical practice.

MATERIALS AND METHODS

All patients who received the graft between October 2019 and October 2020 were prospectively enrolled in an observational, multicenter national registry. The primary endpoint was the aneurysm-related 1-year mortality rate. Secondary endpoints included all-cause mortality, technical success, device-related adverse events (AEs) and major complications, secondary reinterventions, endoleaks, target vessel (TV) outcomes, and a center-volume analysis comparing mortality and secondary reintervention rate between expert centers (>15 F/BEVAR per year) and nonexpert centers (≤15 F/BEVAR per year).

RESULTS

Ninety-seven patients from 28 centers were treated. Aneurysms types included juxta-renal and short neck (84.6%), pararenal (5.2%), paravisceral (3.1%), and type IV thoracoabdominal (2.5%). Configurations with 1, 2, 3, and 4 fenestrations were used in 2, 12, 18, and 65 cases, respectively, totaling 350 TVs. Technical success was 98.0%, with 1 type Ic and 1 type IIIc endoleak. Mean follow-up was 468 days. Ten patients died, with 8 deaths (8.2%) due to non-aortic causes and 2 deaths (2.1%) from unknown causes. The estimated 1-year survival rate was 92.7% (95% CI: 87.8-98.1%). The reintervention rate at 30 days was 11.3% and the estimated reintervention rate at 1 year was 21.6% (95% CI: 12.7-29.6%). No type Ia endoleak occurred during follow-up. Three type III endoleaks occurred and required reintervention. Three TV occlusion occurred, yielding a 1-year TVI-free rate of 92.4% (95% CI: 89.4-99.3). No device-related major complication was recorded, and 3 device-related AEs occurred: 1 limb migration, 1 limb kinking and 1 limb thrombosis. There was no statistically significant difference in mortality and survival without reintervention between expert and nonexpert centers (Log rank p=0.52 and p=0.16, respectively).

CONCLUSION

The fenestrated Anaconda device demonstrated acceptable early and at 1-year safety and efficacy for treating primarily juxta-renal and short-neck aortic aneurysms, in centers with varying levels of experience.

CLINICAL IMPACT

The Anaconda Fenestrated, as the second commercially available custom-made device for complex endovascular aortic surgery, might adress some anatomical challenges. Following market authorization, this registry presents the 1-year outcomes of real-world device usage in a large number of centers, including small clinics. The results indicate that the device provided adequate efficacy and safety for treating mostly juxta-renal and short neck aneurysms, with notable improvement in technical success rate compared to older reports.

Endograft Anaconda in Endovascular Aneurysm Repair: A Systematic Review of Literature and Meta-Analysis

BACKGOUND

The number of endovascular abdominal aortic aneurysm repairs (EVARs) has surpassed the number of open surgical repair of AAAs worldwide with a great variety of endografts being available. The aim of this study is to conduct a systematic review of the literature and meta-analysis of studies reporting patients with infrarenal abdominal aortic aneurysm (AAA) subjected to EVAR with the Anaconda endograft.

METHODS

We performed a systematic review of multiple electronic databases for studies including patients with infrarenal AAA who were subjected to elective EVAR with Anaconda endograft exclusively. We conducted a proportional meta-analysis cumulating the results of the included studies. The endpoints were first month overall mortality, first and second-year survival after EVAR, AAA-related deaths, incidence of endoleaks, endograft migration, endograft occlusion, open conversion, and primary and secondary technical success. The mean value for each separate studied factor was calculated, and the respective percentage or incidence was extracted so that it can be compared to endograft outcome studies in the literature. We assessed the methodologic quality of studies by using the Briggs Institute critical appraisal tool.

RESULTS

Seven observational studies were found including 954 patients (males 91.9%, mean age 73.38 ± 6.97 years). The mean transverse diameter of AAAs was 56.83 ± 9.97 mm. The mean proximal aortic neck diameter and length were 23.06 ± 3.33 mm and 24.14 ± 12.16 mm, respectively. Increased aortic neck calcification and aortic neck thrombus were present in 12.5% of patients. The 30-day overall mortality post-EVAR was 1.3%, 1 and 2-year survival rates were 95.9% and 91.4%, respectively. The mean follow-up period in the studies was 46.59 ± 15.5 months. AAA-related mortality was 1.3%. Primary technical success was 97.9% and secondary success was 99.3%. Open conversion was required in 3.4% of all patients (0.6% during the primary operation [Prim. Op]). The most common endoleak was type II, reported in 17.4% of all patients. Early type Ia endoleak was reported in 1.5% of patients and late type Ia in 1.7%. Overall, 2 endoleaks type III and 1 type IV were reported. Endograft migration occurred in 1.7% of patients. Main body and/or one/both iliac legs thrombotic occlusion was found totally in 7.6% of patients (5 main body occlusions and 64 iliac leg occlusions).

CONCLUSIONS

The use of Anaconda endograft in electively treated patients with infrarenal AAAs presented good results with high technical success and low postoperative and mid-term complications, except for an increased incidence of stent-graft thrombosis, which seems to be the "Achilles heel" of the device.

Ultrasound Particle Image Velocimetry to Investigate Potential Hemodynamic Causes of Limb Thrombosis After Endovascular Aneurysm Repair With the Anaconda Device

PURPOSE

To identify potential hemodynamic predictors for limb thrombosis (LT) following endovascular aneurysm repair with the Anaconda endograft in a patient-specific phantom.

MATERIALS AND METHODS

A thin-walled flow phantom, based on a patient's aortic anatomy and treated with an Anaconda endograft, that presented with a left-sided LT was fabricated. Contrast-enhanced ultrasound particle image velocimetry was performed to quantify time-resolved velocity fields. Measurements were performed in the same phantom with and without the Anaconda endograft, to investigate the impact of the endograft on the local flow fields. Hemodynamic parameters, namely vector complexity (VC) and residence time (RT), were calculated for both iliac arteries.

RESULTS

In both limbs, the vector fields were mostly unidirectional during the peak systolic and end-systolic velocity phases before and after endograft placement. Local vortical structures and complex flow fields were observed at the diastolic and transitional flow phases. The average VC was higher (0.11) in the phantom with endograft, compared to the phantom without endograft (0.05). Notably, in both left and right iliac arteries, the anterior wall regions corresponded to a 2- and 4-fold increase in VC in the phantom with endograft, respectively. RT simulations showed values of 1.3 to 6 seconds in the phantom without endograft. A higher RT (up to 25 seconds) was observed in the phantom with endograft, in which the left iliac artery, with LT in follow-up, showed 2 fluid stasis regions.

CONCLUSION

This in vitro study shows that unfavorable hemodynamics were present mostly in the limb that thrombosed during follow-up, with the highest VC and longest RT. These parameters might be valuable in predicting the occurrence of LT in the future.

CLINICAL IMPACT

This in-vitro study aimed to identify potential hemodynamic predictors for limb thrombosis following EVAR using ultrasound particle image velocimetry (echoPIV) technique. It was shown that unfavorable hemodynamic norms were present mostly in the thrombosed limb. Owing to the in-vivo feasibility of the echoPIV, future efforts should focus on the evaluation of these hemodynamic norms in clinical trials. Thereafter, using echoPIV as a bedside technique in hospitals becomes more promising. Performing echoPIV in pre-op phase may provide valuable insights for surgeons to enhance treatment planning. EchoPIV is also applicable for follow-up sessions to evaluate treatment progress and avoid/predict complications.

Renal and Visceral Artery Configuration During the First Year of Follow-Up After Fenestrated Aortic Aneurysm Repair Using the Anaconda Stent-graft: A Prospective Longitudinal Multicenter Study With ECG-Gated CTA Scans

OBJECTIVE

The performance of fenestrated endovascular aortic aneurysm repair (FEVAR) may be compromised by complications related to the dynamic vascular environment. The aim of this study was to analyze the behavior of FEVAR bridging stent configurations during the cardiac cycle and during follow-up to improve our understanding on treatment durability.

DESIGN

Twenty-one patients presenting with complex abdominal aortic aneurysms (AAAs; 9 juxtarenal/6 pararenal/3 paravisceral/1 thoracoabdominal aortic aneurysm type IV), treated with a fenestrated Anaconda (Terumo Aortic, Inchinnan, Scotland, UK) with Advanta V12 bridging stents (Getinge, Merrimack, NH, USA), were prospectively enrolled in a multicenter observational cohort study and underwent electrocardiogram (ECG)-gated computed tomographic angiography (CTA) preoperatively, at discharge, 7-week, and 12-month follow-ups.

METHODS

Fenestrated endovascular aortic aneurysm repair stability was assessed considering the following variables: branch angle as the angle between the aorta and the target artery, end-stent angle as the angle between the end of the bridging stent and the native artery downstream from it, curvature and tortuosity index (TI) to describe the bending of the target artery. Body-bridging stent stability was assessed considering bridging stent flare lengths, the distances between the proximal sealing stent-ring and fenestrations and the distance between the fenestration and first apposition in the target artery.

RESULTS

Renal branch angles significantly increased after FEVAR toward a perpendicular position (right renal artery from median 60.9°, inter quartile range [IQR]=44.2-84.9° preoperatively to 94.4°, IQR=72.6-99.8°, p=0.001 at 12-month follow-up; left renal artery [LRA], from 63.7°, IQR=55.0-73.0° to 94.3°, IQR=68.2-105.6°, p<0.001), while visceral branch angles did not. The mean dynamic curvature only decreased for the LRA from preoperative (3.0, IQR=2.2-3.8 m-1) to 12-month follow-up (1.9, IQR=1.4-2.6 m-1, p=0.027). The remaining investigated variables did not seem to show any changes over time in this cohort.

CONCLUSIONS

Fenestrated endovascular aortic aneurysm repair for complex AAAs using the Anaconda fenestrated stent-graft and balloon-expandable Advanta V12 bridging stents demonstrated stable configurations up to 12-month follow-up, except for increasing renal branch angles toward perpendicular orientation to the aorta, yet without apparent clinical consequences in this cohort.

CLINICAL IMPACT

This study provides detailed information on the cardiac-pulsatility-induced (dynamic) and longitudinal geometry deformations of the target arteries and bridging stents after fenestrated endovascular aortic aneurysm repair (FEVAR) up to 12-month follow-up. The configuration demonstrated limited dynamic and longitudinal deformations in terms of branch angle, end-stent angle, curvature, and tortuosity index (TI), except for the increasing renal branch angles that go toward a perpendicular orientation to the aorta. Overall, the results suggest that the investigated FEVAR configurations are stable and durable, though careful consideration of increasing renal branch angles and significant geometry alterations is advised.

Differences in Cardiac-Pulsatility-Induced Displacement and Geometry Changes between the Cook ZBIS and Gore IBE: Postoperative Comparison Using ECG-Gated CTA Scans

To what extent the stentgraft design of iliac branch devices (IBDs) relates to dynamic deformation is currently unknown. Therefore, this study aimed to quantify and compare displacement and geometry changes during the cardiac cycle of two common IBDs. This paper presents a two-center trial with patients treated with a Zenith bifurcated iliac side (ZBIS) or Gore iliac branch endoprosthesis (IBE). All patients underwent a retrospective electrocardiogram (ECG)-gated computed tomographic angiography (CTA) during follow-up. Cardiac-pulsatility-induced displacement was quantified for the following locations: (neo) bifurcation of the aorta, IBD flow divider, distal markers of the internal iliac artery (IIA) component and first IIA bifurcation. Geometrical parameters (length, tortuosity index, curvature and torsion) were quantified over centerlines. Displacement was more pronounced for the IBE than the ZBIS, e.g., craniocaudal displacement of 0.91 mm (0.91-1.13 mm) vs. 0.57 mm (0.40-0.75 mm, p = 0.004), respectively. The IBDs demonstrated similar geometrical parameters in the neo-common iliac artery and distal IIA, except for the larger dynamic curvature and torsion of the distal IIA in IBEs. The IBEs showed more dynamic length and curvature change compared to the ZBIS in the stented IIA. The IIA trajectory showed more pronounced deformation during the cardiac cycle after placement of an IBE than a ZBIS, suggesting the IBE is more conformable than the ZBIS.