Primary safety and efficacy endpoints for the Nellix system (Endologix) investigational device exemption (IDE) trial have been achieved at one year, with “very low morbidity and mortality and high procedural and treatment success,” according to Jeffrey Carpenter, Cooper Medical School of Rowan University, Camden, USA, at the Vascular Annual Meeting (9–11 June, National Harbor, USA).
“The Nellix System for endovascular aneurysm sealing (EVAS) is a novel approach to abdominal aortic aneurysm treatment whereby polymer is employed to fill the aneurysm sac,” explained Carpenter, reporting the one-year results of the IDE pivotal trial.
Twenty-nine US (26) and European (three) sites with 150 patients were involved in the IDE trial, for which inclusion criteria required an asymptomatic infrarenal abdominal aortic aneurysm diameter ≥5cm (or 4.5cm with ≥0.5cm growth in the prior six months, or >1.5x normal aorta) with proximal neck length >10mm and angle <60 degree, common iliac blood lumen diameter 9–35mm, and sac blood lumen diameter ≤6cm. The majority (95%) of patients were males, iliac diameters ranged from 11–53mm, with a mean of 20mm. Follow-up included computed tomography angiography scans performed at 30 days, six months and one year, evaluated by a core laboratory.
Carpenter reported 100% procedural success, with an average implant time of 30 minutes and an average discharge from hospital time of 1.1 days. All but one eligible patient (n=143, 99.3%) completed one-year follow-up. The 30-day major adverse event rate was 2.7%, achieving the primary safety endpoint (<56%—the SVS open repair control group rate). At one year, treatment success was 94%, meeting the effectiveness endpoint (>80%).
The major adverse events included six deaths, one bowel ischaemia, one myocardial infarction, two renal failures, two respiratory failures and three strokes. Freedom from major adverse events was 93.3%, freedom from mortality was 96%, freedom from abdominal aortic aneurysm-related mortality was 99%, freedom from rupture was 99%, freedom from conversion was 99%, and freedom from device-related secondary interventions was 96.6%. Six secondary interventions were performed in five patients for treatment of rupture (one), type Ia endoleak (two), limb thrombosis (two), and renal artery coverage (one). Aneurysm sac diameter at one year was stable or decreased in 134 (98.5%) of evaluable patients. Endoleaks were present in four (3.1%) patients at one year (one type Ib and three type II). Carpenter also reported that there were three device migrations >10mm and two instances of sac growth >5mm, although none of these were clinically significant.
“These data show the lowest overall endoleak (3.1%) and secondary intervention (3.3%) rates reported at one year as compared with other FDA-approved EVAR devices,” said Carpenter, with comparable outcomes for other criteria. “The one-year IDE results demonstrate that EVAS with Nellix is successful at treating a broad range of infrarenal abdominal aortic and common iliac artery aneurysms.” Longer term follow-up, currently in progress, “is needed to ensure the durability of EVAS,” concluded Carpenter.
With any new concept such as this, a learning curve must be considered. Carpenter said, “It is very different from EVAR. You can gain familiarity very quickly with these steps, probably within five to 10 cases. As you try more and more difficult anatomies, there are nuances. It is deceptively simple and though at first glance it might appear to be like kissing stents, the addition of polymer has a lot of technical aspects to it that need to be learned.”
Carpenter also noted that although “there is no restriction on the size of the aneurysm that can be treated with EVAS, but since the endobags and the polymer must seal the flow lumen there is a limitation there—6cm is specified on the instructions for use for the device.”