Diagnosis and relining techniques for delayed type IIIB endoleaks with the second-generation AFX endograft

Exploring Type IIIb Endoleaks: A Literature Review to Identify Possible Physical Mechanisms and Implications

Endoleaks are common complications following endovascular aneurysm repair (EVAR). They can be classified into low-pressure and high-pressure endoleaks. High-pressure endoleaks, which include Type I and Type III endoleaks, pose a significant risk of rupture and require urgent treatment. The aim of our study is to review published case reports and case series to assess the impact of Type IIIb endoleaks in EVAR and to identify possible mechanisms contributing to these endoleaks. This review targeted case reports and case series published between January 1998 and December 2022. A total of 62 case reports and case series were identified, encompassing 156 patients with Type IIIb endoleaks. Data collection was performed by three consultants who thoroughly discussed each report before registering it into an analyzable data set. Our analysis revealed that, beyond material imperfections, certain endograft configurations or conformations, endograft redundancy, and the physical forces acting on the grafts may lead to increased stress on specific parts of the endografts, potentially exceeding their design limits. Factors contributing to redundancy and unfavorable conformation of the endograft include secondary interventions for any cause (such as other types of endoleaks), EVAR performed outside the instructions for use (IFUs), endograft migrations, or larger initial aneurysm diameter.

Stent Graft Migration Due to Structural Failure Nine Months After Thoracic Endovascular Aortic Repair Using Valiant Navion

Objective

This report presents a case of stent graft migration that was suspected to have occurred due to failure of the Valiant Navion device (Medtronic Inc., Santa Rosa, CA, USA). This case was rare because the broken device was removed from the living patient and examined directly.

Case report

A 69 year old man who had previously undergone thoracic endovascular aortic repair (TEVAR) with arch vessel debranching (axillo-axillary bypass with left common carotid artery bypass) for distal arch aneurysm experienced stent graft (SG) migration 9 months after the primary surgery. Total arch replacement was performed, and the migrated SG was removed. The broken stent ring and suture seams were then found. The patient was discharged on post-operative day 41 and followed up in the outpatient department.

Discussion

Stent graft migration is a relatively rare complication after TEVAR and associated with type I or III endoleak, which can result in serious outcomes. In this case, it was suspected that migration had occurred after TEVAR due to structural failure of the Valiant Navion device; similar cases have been reported previously, suggesting a structural problem with the device. Therefore, other patients treated with the Navion device in the future will require careful follow up.

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.

Late Type III Endoleaks Are Common in Early Generation Endologix AFX Stent Grafts

INTRODUCTION

Early generation Endologix AFX Endovascular AAA Stent Graft devices are at risk of developing type IIIa (intercomponent/overlap-related) as well as type IIIb (fabric tear) endoleaks over time. Current follow-up studies are limited to short (<24 months) and midterm (24-48 months) reports. The purpose of this study was to identify the incidence of type III endoleaks associated with these endografts over a long-term follow-up (>4 years) period and discuss current management strategies.

METHODS

A retrospective single institution cohort analysis of all Endologix AFX endografts implanted 10/2011-10/2016 was performed. Patient characteristics, imaging and follow-up were obtained via chart review. Type III endoleaks were characterized based on Computed tomography (CT) angiogram/operative findings and confirmed by 2 surgeons. Statistical Analysis was performed with SAS v9.4.

RESULTS

Sixty-three patients underwent AFX stent graft implantation for aneurysmal disease. 47 patients comprised the final cohort for analysis after exclusions were made for primary iliac aneurysms as well as off label use of the device (e.g., hypogastric snorkel) or primary occlusive indications. Average age was 73.3 years with longest follow-up 8.7 years (median 5.2). Most AAA (89.2%) were fusiform with initial median diameter 5.5cm. Initial 30-day mortality was 0%. Of the initial cohort, 10 (21.3%) type III endoleaks were treated, of which 6 (60%) were type IIIa and 4 (40%) were type IIIb. By time to event analysis at latest follow-up freedom from type 3 intervention was 48% at 8 years. Median time to type III endoleak discovery was 4.7 years (range 1.1 -7.2 years) an interval that was similar for type IIIa and type IIIb leak types, p=0.73. Patients with type III endoleaks had average sac growth of 1.3cm over the follow-up interval compared to a net decrease for patients without type III endoleaks, p<.0001. Of the 10 patients treated for type III leaks, 7 (70%) underwent complete endovascular re-lining, one (10%) had partial re-lining while 2 (20.0%) underwent open endograft explant with aortic graft reconstruction. Reintervention 30-day mortality was 0% for all approaches.

CONCLUSION

Early generation Endologix AFX stent grafts have a high rate of type III endoleaks, with freedom from type III leak <50% at 8-year follow-up. Most of these are not detected until several years (>4.5) after initial implantation, beyond the range of the follow-up interval of most published reports. Long-term imaging surveillance is critical and a low threshold for complete relining should be considered with any sign of sac enlargement, even if endoleak is not clearly demonstrated in patients with early generation Endologix AFX grafts.

Midterm outcomes of 455 patients receiving the AFX2 endovascular graft for the treatment of abdominal aortic aneurysm: A retrospective multi-center analysis

Since being introduced into clinical practice the AFX family of endografts has undergone labelling updates, design and manufacturing changes to address a Type III failure mode. The published literature on the performance of the current endograft-AFX2 -is limited to small series with limited follow up. The present study reports the largest series of patients implanted with AFX2 for the treatment of abdominal aortic aneurysms. The study was a retrospective, 5 center study of patients receiving an AFX2 endograft from January 2016 until Dec 2020. Electronic case report forms were provided to four of the centers, with one additional site providing relevant outcomes in an independent dataset. Relevant outcomes were reported via Kaplan-Meier analysis and included all-cause mortality, aneurysm-related mortality, post EVAR aortic rupture, open conversion, device related reinterventions and endoleaks. Among a cohort of 460 patients, 405 underwent elective repair of an AAA, 50 were treated for a ruptured AAA, and 5 were aorto-iliac occlusive disease cases. For the elective cohort (mean age 73.7y, 77% male, mean AAA diameter 5.4cm), the peri-operative mortality was 1.7%. Freedom from aneurysm-related mortality was 98.2% at 1,2,3 and 4 years post-operatively, there were no post-operative aortic ruptures, and 2 patients required open conversion. Freedom from Type Ia endoleaks was 99.4% at 1, 2, 3 and 4 years. Freedom from Type IIIa and Type IIIb endoleaks were 100% and 100% (year 1), 100% and 99.6% (year 2), 99.4% and 99.6% (year 3), 99.4% and 99.6% (year 4) respectively. Freedom from all device-related reintervention (including Type II endoleaks) at 4 y was 86.8%. The AFX2 endograft appears to perform to a satisfactory standard in terms of patient centric outcomes in mid-term follow up. The Type Ia and Type III endoleaks rates at 4y appear to be within acceptable limits. Further follow up studies are warranted.

A preliminary analysis of late structural failures of the Navion stent graft in the treatment of descending thoracic aortic aneurysms

OBJECTIVE

Patients in the Valiant Evo U.S. and international clinical trials had positive short-term outcomes; however, late structural failures, including type IIIb endoleaks have been recently discovered. Type IIIb endoleaks are serious adverse events because the repressurization of the aneurysm sac increases the risk of rupture. The purpose of the present study was to detail the imaging patterns associated with the structural failures with the aim of increasing awareness of failing graft presentation, early recognition, and prompt treatment.

METHODS

The Valiant Evo clinical trial was a prospective, single-arm investigation of a thoracic stent graft system. With the recent late structural failures, sites were requested to submit all available imaging studies to date to allow the core laboratory to assess for structural failures such as type IIIb endoleaks, stent ring fractures, and stent ring enlargement. Of the 100 patients originally enrolled in the trial from 2016 to 2018, the core laboratory assessed the imaging studies performed at ≥1 year for 83 patients.

RESULTS

No structural failures of the graft were reported through 1 year of follow-up. At 1 to 4 years, graft structural failures were detected in 11 patients with descending thoracic aortic aneurysms. Of the 11 patients, 5 had a type IIIb endoleak. Four of the five had imaging findings showing stent fractures consistent with the location of the graft seam and one had a type IIIb endoleak attributed to calcium erosion with no stent fracture or ring enlargement. Of the four patients with stent fracture in line with the graft seam, three underwent a relining procedure that successfully excluded the type IIIb endoleak. One of these three patients died 4 days later of suspected thoracic aortic rupture because the distal thoracic endovascular aortic repair extension had been landed in a previously dissected and fragile section of the aorta. The remaining six patients had had stent ring enlargement. One of the six patients had had persistent aneurysm expansion from the time of implantation onward and had died of unknown causes. The remaining five patients have continued to be monitored.

CONCLUSIONS

In the present preliminary analysis, the imaging patterns associated with type IIIb endoleaks, stent fractures, and stent ring enlargement appear to be related to the loss of seam integrity or detachment of the stent rings from the surface of the graft material. The imaging patterns we have detailed should be closely monitored using computed tomography angiography surveillance to allow structural failures to be promptly identified and treated.

Parallel Placement of Excluder Legs for the Treatment of a Type IIIb Endoleak Using AFX2

Endoleak is a major complication of endovascular aneurysm repair (EVAR). Type IIIb endoleaks, which are caused by endograft fabric disruption, are relatively rare. Although relining of the previously placed endograft with another main endograft is considered an ideal approach, it is sometimes difficult. The efficacy of parallel placement of Excluder legs has been reported in various settings. Here, we report the successful treatment of a type IIIb endoleak with parallel placement of Excluder legs during EVAR by using an AFX2 device.