Study Evaluates Relationship of Endologix's Nellix EVAS Device Midterm Results and IFU
December 5, 2018—The Society for Vascular Surgery (SVS) announced the publication of findings from a large, single-center experience using the Nellix endovascular aneurysm sealing (EVAS) device (Endologix, Inc.) that reveals a relationship between the device's instructions for use (IFU) and midterm results. The study by Katherine Stenson, MD, et al is available online ahead of print in the January 2019 issue of Journal of Vascular Surgery.
Dr. Stenson led investigators from St. George’s Vascular Institute in London, United Kingdom.
According to SVS, the study investigators evaluated 150 consecutive EVAS procedures performed at their institution between 2013 and 2015. The patient cohort demographics included median age of 77 years (70–81); 87% men; and American Society of Anesthesiology Class 4, 66%. Aneurysm characteristics were: median diameter, 6.2 cm; adverse neck morphology, 46% (including length < 10 mm in 17%; diameter > 32 or < 18 mm in 9%; angulation > 60º in 15%).
At a median follow-up of 687 days (interquartile range, 463–897 days), the investigators found unresolved endoleaks (type Ia, 1.3%; type Ib, 0.7%; type II, 2.7%; type III, 0%) and seven secondary ruptures (six survived; one of the seven were treated within IFU).
In the SVS announcement, Dr. Stenson commented, “Adverse proximal neck anatomy remains the Achilles heel for endovascular aneurysm treatment. Previous studies have shown us that adverse neck anatomy is associated with poorer outcomes and a greater need for reintervention.”
She continued, “When the Nellix graft was first made commercially available, it was hoped that it might be able to treat a greater proportion of aneurysms with morphologic features within the manufacturer’s IFU, particularly with regard to the aneurysm neck. It was thought that the polymer sealing technology would be able to create an adequate seal even within short, conical, and angulated necks.”
Furthermore, she noted, “When this clinical program was initiated, the global experience with this device was limited. As a result, during the time frame of this study, the technical aspects of the procedure have evolved and become refined. Our experience and the global experience have led to a better understanding of which aneurysms should be treated with the Nellix device.”
Dr. Stenson concluded, “The potential problems surrounding proximal and distal sealing and intraluminal thrombus in the sac led to a tightening of the IFU in 2016. The rates of migration, type Ia endoleak, and secondary rupture are higher than reported in other EVAR studies; however, type II endoleak is lower. Retrospective morphologic analysis of the aneurysms before and after treatment has shown the importance of placing the stents at the level of the renal arteries to maximize the aortic neck.”
According to SVS, this study of an elderly cohort of patients with challenging aortic anatomy provides evidence for the safety and effectiveness of the Nellix system, particularly after refinements to the device's IFU in 2016. SVS advised that these are relatively early results and the durability of the device must be determined; therefore, continued follow-up to a minimum of 5 years is essential. Importantly, it remains critical to apply this technology within the IFU where possible.