Τhe AFX unibody bifurcated unibody aortic endograft for the treatment of abdominal aortic aneurysms: current evidence and future perspectives

Safety Evaluation of Unibody Endografts for Abdominal Aortic Aneurysm Repair: A Systematic Review and Meta-Analysis

BACKGROUND

The unibody bifurcated aortic endograft (AFX/AFX2) has emerged as a treatment option for abdominal aortic aneurysms (AAAs). This systematic review and meta-analysis aimed to evaluate the safety of the unibody endograft.

METHODS

A literature search was conducted in Cochrane Library, Scopus, Web of Science, and PubMed. Studies assessing the unibody endograft for AAA repair between 2014 and 2023 were included. The defined primary outcomes were the incidences of type I, II, and III endoleaks. The secondary outcomes were access site problems, aneurysm-related mortality, aneurysm rupture, all-cause mortality, aneurysm sac growth, limb occlusion, stent graft migration, and technical success rate.

RESULTS

Fourteen studies including 12 observational studies and 2 randomized controlled trials were included in the systematic review. The meta-analysis included 10 studies with 12,690 patients that reported the measured outcomes, and excluded 4 studies that did not. Type II endoleaks had the highest incidence of 12% (95% confidence interval [CI]: 4-20%), followed by type III endoleaks with an incidence of 3% (95% CI: 1-5%). The incidence of type I endoleaks was 1% (95% CI: 0-2%). A subgroup analysis by follow-up duration showed that type II endoleak incidence was higher after 1 to 2 years of follow-up than 3 to 4 years of follow-up. The incidence of aneurysmal mortality was 2% (95% CI: 0-7%), limb occlusion was 1% (95% CI: 0-1%), stent graft migration was 1% (95% CI: 0-2%), aneurysmal rupture was 6% (95% CI: 2-11%), access site problems were 7% (95% CI: 2-13%), aneurysm sac growth was 2% (95% CI: 0-4%), all-cause mortality was 21% (95% CI: 4-38%), and technical success rate was 100% (95% CI: 98-100%).

CONCLUSIONS

The unibody endograft is a safe and minimally invasive approach for AAA repair. However, potential complications necessitate close patient follow-up after the intervention.

Guessing the sequence of multiple relinings with AFX and nitinol-based cuff: "A riddle, wrapped in a mystery, inside an enigma"

OBJECTIVE

Knowing the structural and technical features of both the older and newer aortic endografts is an essential tool to understand off-the-shelf combinations of different devices used to treat challenging abdominal aortic aneurysm (AAA) anatomies or failures of previous endovascular aneurysm repairs (EVAR).

METHODS

We present a case of a 72-year-old male with history of AAA and evidence of multiple past EVAR interventions who presented with abdominal pain. With no reliable surgical history, we attempted to delineate the types of different endograft parts implanted and the sequence of relining procedure based on plain X-ray projections and combined computed tomography along with intraoperative angiography.

RESULTS

A tubular endograft was presented with a distal fracture of its endoskeleton, and relined with the same type unibody bifurcate. The latter was extended proximally with an AFX extension of a characteristic radiopaque continuous rim. Angiographic findings intraoperatively excluded the latter as part of the initial procedure. Moreover, an extra nitinol-based cuff was identified centrally.

CONCLUSION

In diagnostic challenges involving multiple relining attempts of different endograft parts, careful analysis of the imaging findings, based on knowledge of the structural and technical features of both the older and newer endografts is necessary for proper diagnosis, identification of potential problems and complications and intervention planning, if needed.

First case of relining an aortic bifurcated bypass graft with the Altura endograft to treat anastomotic aneurysms

OBJECTIVE

Use of classic bifurcated endografts for relining of bifurcated aortic bypass grafts with aneurysms is usually precluded by the short distance between the lowermost renal artery and the aneurysmatic bifurcation, rendering their management challenging.

METHODS

We present the use of the Altura endograft in a case of a 75-year old male with large anastomotic aneurysms in the proximal and the left iliac amastomosis of a bifurcated aortic bypass graft. The Altura endograft consists of two separate components with a proximal D-shaped design. Its braided nitinol endoskeleton is attached only at the proximal and distal ends of the inner surface of the polyester fabric and results in adjustable lengths of the components according to the vessel diameters where they are deployed.

RESULTS

A 24 mm Altura sealed successfully at the native infarenal aortic segment covering the entire distance between the lowermost renal artery and the upper end of external iliac artery, providing successful exclusion of the aneurysms. No iliac extensions were used. The completion angiography showed no endoleaks.

CONCLUSIONS

The unique design of Altura makes it ideal for treatment of anastomotic aneurysms of bifurcated bypass grafts, overcoming anatomic limitations. To the best of our knowledge, this is the first report addressing this crucial issue.

Late Type III Endoleak after Loss of Component Overlap after EVAR with AFX2 Device: A Case Report

Addressing the high incidence of late type III endoleaks in previous AFX models, Endologix upgraded the device material and updated its recommendation regarding component overlap. However, whether upgraded AFX2 models are safe for endoleaks remains controversial. Here we report a case of a 67-year-old male with an AFX2-implanted abdominal aortic aneurysm experiencing a delayed type IIIa endoleak. Aneurysmal sac enlargement occurred 36 months post-endovascular aneurysm repair (EVAR), with a computed tomography scan at 52 months revealing component overlap loss and a significant type IIIa endoleak. We performed endograft explantation and endoaneurysmal aorto-bi-iliac interposition grafting. Our findings suggest that sufficient component overlap is necessary when using an AFX2 endograft outside the manufacturer's instructions for use to prevent late type IIIa endoleaks. Moreover, patients who undergo EVAR with AFX2 for tortuous large aortic aneurysms should be carefully monitored for conformational changes.

Midterm outcomes of AFX2 endografts used in combination with aortic cuffs

OBJECTIVE

Type III endoleaks after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysms (AAAs) with the Endologix unibody endograft remain a major concern, despite fabric, system, and instructional updates. The purpose of this study was to examine real-world outcomes of repairing AAAs using the current version of the AFX2 main body in combination with an aortic cuff, specifically focusing on type III endoleaks and morphological changes of the endograft.

METHODS

We recruited facilities in Japan that used AFX2 combined with an aortic cuff for at least five cases between April 2017 and March 2018. A total of 175 cases in 24 facilities were analyzed. Patients' background information, including anatomic factors, operative findings, device component variations, and midterm outcomes at 3 years after the EVAR were collected. The data on computed tomography scans from cases registered as types I and III endoleaks and migration from each institute were sent to our department for verification.

RESULTS

The mean patient age was 74.6 ± 8.1 years, and 48 cases (27%) were saccular aneurysms. The mean fusiform and saccular AAA diameters were 50.5 ± 5.8 mm and 43.5 ± 8.9 mm, respectively. No in-hospital deaths occurred. Data at 3 years, including computed tomography images, of 128 cases were analyzed. Overall survival, freedom from aneurysm-related mortality, and freedom from reintervention rates at 3 years were 85.8%, 99.3%, and 87.3%, respectively. There were three, one, and three cases of types I, IIIa, and IIIb endoleaks without sac dilatations, respectively. Among five migration cases, one case of aortic cuff migration presented as a type Ia endoleak, and four cases demonstrated sideways displacement, one of which presented as a type IIIa endoleak. The sac regression and enlargement rates at 3 years were 41.4% and 20.5% in the fusiform group and 44.2% and 16.7% in the saccular group, respectively. The proximal neck diameter slightly increased from 20.8 ± 2.7 mm before the EVAR to 22.2 ± 4.6 mm after the repair.

CONCLUSIONS

Midterm outcomes of the AFX2 used in combination with an aortic cuff were acceptable, considering the rates of types I and III endoleaks. However, there were cases of sideways displacement that could cause future type IIIa endoleaks. When the AFX2 is used in combination with an aortic cuff, close surveillance for endograft deformations and subsequent adverse events, including type III endoleaks, is needed.

Early Clinical Outcomes of the Active Seal Technology of the AFX Endovascular Aortic Aneurysm System With the VELA Cuff for Patients With a Conical Proximal Neck

PURPOSE

To evaluate the efficacy of the Active Seal technology employed in the AFX endovascular aortic aneurysm system (AFX), during endovascular aneurysm repair (EVAR) in patients with abdominal aortic aneurysms (AAAs) having a conical proximal neck.

MATERIALS AND METHODS

A retrospective analysis of the EVAR for AAA with a conical proximal neck using the AFX was performed at 17 Japanese hospitals between January 2016 and August 2020. The conical proximal neck was defined as a cone-shaped proximal neck, with more than 10% diameter increase within a 15 mm length at the proximal landing zone. All anatomical analyses were performed in the core laboratory, and cases with parallel walls within the proximal neck adequate for the landing zone were excluded from the study.

RESULTS

This study included 53 patients, but only 39 patients (mean age, 76.6 ± 6.7 years; 87.0% males; mean aneurysm diameter, 52.0 ± 8.0 mm) were analyzed after being characterized as having a pure conical neck by the core laboratory. The mean proximal neck diameters at the lower renal artery and proximal edge of the aneurysm were 20.0 ± 2.9 mm and 27.5 ± 4.9 mm, respectively. The mean proximal neck length was 21.5 ± 6.0 mm. Instructions for use violations other than the conical neck were observed in 15 patients (38.5%). The VELA cuff was used in all cases; however, additional proximal cuff was required in 9 more cases (23.1%). The Active Seal technology was able to significantly extend the proximal sealing zone from 21.5 ± 6.0 to 26.0 ± 12.2 mm (p = .047). Thirty-six patients completed the 12-month follow-up (one patient was lost to follow-up, and 2 patients died from causes unrelated to the aneurysm), and there were no type-1a and 3 endoleaks with only one reintervention (2.6%) related to type 1b endoleak in the 12-month period. Furthermore, there was no significant enlargement of the proximal neck diameter at 12 months (at 1 month: 20.6 ± 3.4 mm and at 12 months: 21.3 ± 3.8 mm; p = .420).

CONCLUSION

The Active Seal technology of the AFX significantly extended the proximal seal zone and no type-1a endoleak and proximal neck dilation was observed in patients with conical proximal neck at 12 months.

The Altura endograft system for endovascular aneurysm repair: presentation of its unique design with clinical implications

INTRODUCTION

The Altura aortic endograft for the treatment of abdominal aortic aneurysms (AAA) consists of two separate components with a proximal double D-shaped design. The braided endoskeleton of the endograft is attached only at the proximal and distal ends of the inner surface of the fabric resulting in adjustable length of the Altura components. To ensure optimal orientation and sealing, the design of Altura permits collapse, readjustment, and deployment of the repositioned D-shaped endografts.

AREAS COVERED

Since this new endograft design by Lombard presents unique characteristics, the aim of this article is to present its unique structure and deployment method and discuss its applicability, indications and associated concerns.

EXPERT OPINION

The Altura endograft revolutionizes the mechanism of infrarenal sealing by containing no main body at all. This feature allows ideal treatment of AAA with considerable offset of the renal arteries and permits also relining in cases of failing endografts or in cases where the short length of existing structures precludes deployment of conventional bifurcated endografts.

Surgery for late type Ia/IIIb endoleak from a fabric tear and stent fracture of AFX2 stent graft

Technical improvements and labeling updates of the AFX2 stent graft (Endologix Inc, Irvine, CA) seemed to have solved the known issues of its previous generation (AFX Strata). Although most endograft failures after endovascular abdominal aortic aneurysm repair will be managed endovascularly, a small subset of patients will still require secondary open conversion. Partial or complete endograft removal can be required, mainly dependent on the characteristics of the stent graft previously placed. We have report a case of secondary open conversion for late type Ia/IIIb endoleak due to stent fracture and fabric tear of the AFX2 stent graft 3 years after endovascular abdominal aortic aneurysm repair.

Elucidating the role of the AFX2 endograft in endovascular treatment of aortic pathology

OBJECTIVE

The purpose of this study is to elucidate the role of the AFX2 platform in the endovascular treatment of aortic pathology.

METHODS

All procedures by a single surgeon resulting in implantation of a bifurcated unibody stent graft were retrospectively reviewed. Indications for selection of the AFX2 endograft in each case were evaluated. Aortic anatomy was determined via review of pre-operative computed tomography (CT) scans. Cumulative event probabilities for endoleak, reintervention, and mortality were estimated. Patient and procedural details were described using mean, standard deviation, medians, and interquartile range (IQR). Kaplan-Meier survival analysis estimated freedom from mortality and reintervention. Cumulative incidence probabilities were calculated as one minus the Kaplan-Meier estimator.

RESULTS

Between March 2018 and December 2020, the author (NN) used 142 aortic endografts in 142 patients. Of these, 46 (32.4%) were AFX2 endografts and the remaining were modular bifurcated devices, predominantly Medtronic Endurant II and Terumo Treo. No AFX-Strata or AFX-Duraply devices were placed. Amongst the patients who received an AFX2, mean age was 71.3 +/- 9.8 years with 84.8% male. Median operative time was 116 (86-166) minutes, with contrast dose of 79 (41-120) milliliters and fluoroscopy time of 12 (8.6-18) minutes. Overall, 78.3% (n=36) of AFX2 devices were placed in aortas with maximum true lumen diameter <5.0cm. Median postoperative follow-up was 1.7 years (IQR 1.0-2.4 years), with a maximum follow-up of 3.6 years. There was 1 patient lost to follow-up at 5 months. The 2-year incidence of type II endoleak, reintervention, and all-cause mortality was 12.7% (95% CI, 0-29.6%), 2.2% (95% CI, 0-6.3%), and 11.3% (95% CI, 0.1-2.1.2%), respectively. There were no type I or III endoleaks.

CONCLUSION

The AFX2 endograft plays a safe and effective role in treatment of infrarenal aortic pathologies that may be otherwise more technically challenging for traditional modular, bifurcated devices.

Use of the AFX Stent Graft in Patients with Extremely Narrow Aortic Bifurcation: A Multicenter Retrospective Study

Introduction

This study analyzed the patient outcomes following endovascular aortic aneurysm repair (EVAR) for infrarenal aortic pathologies with very narrow aortic bifurcations using the AFX stent graft.

Methods

The data was retrieved from the archived medical records of 35 patients treated for abdominal aortic aneurysm (AAA) (48.6%) or penetrating aortic ulcer (PAU) (51.4%) with very narrow aortic bifurcation between January 2013 and May 2020. Patient survival, freedom from endoleak (EL), and limb occlusion were estimated applying the Kaplan–Meier method.

Results

The mean follow-up time was 20.4 ± 22.8 months. The mean aortic bifurcation diameter was 15.8 ± 2.2 mm. Technical success was 100%, and no procedure-related deaths occurred. Two type II ELs occurred within 30-day follow-up. We observed one common iliac artery stenosis at four months and one type III EL at 54 months in the same patient, both of which required re-intervention. Overall patient survival was 95 ± 5% (AAA: 100%; PAU: 89 ± 10%), freedom from limb occlusion was 94 ± 5% (AAA: 91 ± 9%; PAU: 100%), freedom from type II EL was 94 ± 4% (AAA: 88 ± 8%; PAU: 100%), and freedom from EL type III was 83 ± 15% (AAA: 80 ± 18%; PAU: 100%) at the end of the follow-up period.

Conclusions

Very narrow aortic bifurcations may predispose patients to procedure-related complications following EVAR. Our results suggest a safe use of the AFX stent graft in such scenarios. The overall short- and long-term procedure-related patient outcomes are satisfying albeit they may seem superior for PAU when compared to AAA.

Computational Fluid Dynamic Analysis Supports the Hemodynamic Stability of Hybrid Combinations With the AFX Bifurcate and Nitinol-Based Proximal Segments in Solutions of Failed Endovascular Aneurysm Repair

Hybrid endograft combinations of two or more different types of covered stents are rarely reported to treat complex abdominal aortic aneurysm cases or primary and secondary endoleaks. Clinical and laboratory data regarding the clinical efficacy and mechanical stability of such combinations are lacking. Based on a recently published case report, we describe and comment on the hemodynamic profile of a representative simulated hybrid case of AFX and Nitinol-based proximal cuff and support the stability of this combination in non-angulated cases.

Unibody bifurcated aortic endograft: device description, review of the literature and future perspectives

The unibody (Powerlink/AFX/AFX2) Endovascular AAA device (Endologix Inc., CA, USA) presents a unique design with its long main body and two innate limbs. The device is designed to be deployed and sits on the native aortoiliac bifurcation and represents the only one-piece bifurcated endograft designed to use anatomical fixation for endograft stabilization. According to published literature, the unibody device seems to represent a valid choice in the treatment of abdominal aortic aneurysms. This particular device would seem to satisfactorily perform even in the treatment of more compressed aneurysms (also in off-label association with parallel grafts) and in occlusive pathologies. Ongoing studies will provide new real-life data in a large and unselected patient population to better understand the device’s advantages and limitations.

Modeling and Computational Comparison of the Displacement Forces Exerted between the AFX Unibody Aortic Stent Graft and its Hybrid Combination with a Nitinol-based Proximal Aortic Cuff

BACKGROUND

The bifurcated AFX (Endologix, Inc, Irvine, CA, USA) aortic stent-graft is the sole unibody endograft for the management of Abdominal Aortic Aneurysms (AAA). In order to improve the AFX central sealing and clinical efficacy in challenging cases, a replacement of the central chromium-cobaltium AFX extension with a Nitinol-based proximal aortic cuff has been suggested. Yet, comparative data regarding the hemodynamic performance of this design is missing. Aim of this study was to compare the displacement forces (DF) acting on the hybrid AFX-Endurant design, with the classic AFX and Endurant endografts, in angulated and non-angulated cases based on patient-specific Computational Fluid Dynamics (CFD) simulations.

METHODS

3D endograft models of 11 treated AAA cases were reconstructed from Computed Tomography Angiography (CTA) imaging data: 5 cases of AFX, 3 cases of the combination AFX-Endurant and 3 cases of the classic Endurant design. The DF on the main-body, the iliac limbs, and the entire stent-graft was calculated by processing the velocity and pressure fields generated by pulsatile CFD simulations.

RESULTS

The range of total DF (acting on the whole endograft structure) in the AFX, hybrid AFX-Endurant and Endurant group was 2.5-5.2N, 2.0-5.9N and 1.9-2.9N respectively, with the maximum total DF being lower for Endurant. The DF on the main-body of the classic and hybrid AFX cases were higher than the right and left iliac limbs (2.5-4.9N vs. 0.6-5.3N and 0.7-3.6N respectively). Conversely, the DF on the main-body of the Endurant cases was comparable to the force exerted on the right and left limbs. When separating the cases with respect to their neck angulation, the DF on all endograft parts (main-body, limbs) and on the endograft as a whole were lower for the hybrid AFX-Endurant group compared to the classic AFX and Endurant groups, for cases with almost straight neck.

CONCLUSION

The off-label use of the hybrid AFX-Endurant stent-graft does not seem superior to the conventional AFX or Endurant endografts in angulated cases but was associated with lower DF than AFX or Endurant in non-angulated cases. The clinical value and utility of these findings remain to be elucidated.