By Dittmar Böckler
For over two decades endovascular aneurysm repair (EVAR) has been a minimal invasive treatment option for abdominal aortic aneurysms and an alternative to open surgery, especially for older and high risk patients. In addition, EVAR has even been considered to be the treatment of first choice for many patients. Abobe all, patients themselves ask specifically for this treatment.
Multicentre randomised controlled trials (EVAR 1, DREAM, OVER) showed significant perioperative reduction in mortality with EVAR. However, one of the drawbacks, the Achilles‘ Heel of this technique, is the reintervention rate of 3.7% per year and the overall high rate of reinterventions – up to 19% during follow-up. This is mainly caused by endoleaks and migration. These have had tremendeous influence on costs following EVAR.
Ruptures after EVAR are occassionally reported and show an incidence of 0.8% in the EUROSTAR registry despite endovascular aneurysm exclusion. The requirements for new stent grafts are to maintain the early mortality reduction of EVAR, reduce reintervention, reduce surveillance costs, ensure aneurysm stability and progression, and maybe lower profile designs. Technical and device modifications are, therefore, aimed to reduce endoleaks and associated secondary procedures. Many commercially available devices are on the market and some of them already have already been withdrawn. Meanwhile, fourth generation devices are available.
The principle of EVAR is fixation and sealing. Fixation is achieved by stent radial force, device columnar strength, hooks, barbs and suprarenal stents. Seal is achieved by graft wall apposition. Potential weaknesses of the current stent graft designs may be inadaquate sealing and fixation and branch vessels perfusing the aneurysm sac.
The Nellix aneurysm sealing device adresses a new concept of complete anatomic sealing, with no side branch and collateral perfusion and compleete fixation by anatomic apposition. This is acheived by bilateral stents and an endobag filled with biostable polymer. This is the reason why EVAR has been changed to EVAS (endovascular aortic aneurysm sealing) with the Nellix device.
The goals of the new Nellix device, which received CE mark recently, is to address also challenging proximal necks with short irregular, even conical, morphology, to treat aortoiliac disease in order to avoid hypogastric occlusion or the use of side branch devices and to minimise, as previously mentioned, endoleaks and device migration, and to reduce costs during follow-up.
On 4 March 2013 we performed in Heidelberg, Germany, the first two implants in continental Europe, treating two patients with abdominal aortic aneurysms in an elective setting with the new CE-marked Nellix device. Both procedures were performed uneventful and with very short procedural times. The two patients were discharged without any events on day 4.
Andrew Holden and his team in Auckland, New Zealand, Dainis Krievins, Riga, Latvia, and the Stanford group, USA, with Christopher Zarins et al published their early experience with the former Nellix device in JVS 2011:53:574–82 and Eur J Vasc Endovasc Surg 2011;42:38–46, concluding that favourable and adverse anatomy patients can be successfully treated using the Nellix sac-anchoring endoprosthesis. Early results are promising but longer-term studies are needed. Two registries are planned (EVAS I and EVAS II) and enrolment is expected to start in the spring 2013.
If Nellix works, and it looks like (my personal opinion) it does, it will be a game changer. It is fast, and you do not need many wires, catheters and post balooning. It also appears to be easy to avoid cannulation. The device may even work in ruptured aneurysms.
Some questions remain: How to perform follow-up? Is the endoleak classification still applicable with Nellix? How to treat type I endoleak or proximal disease progression? What happens with the polymer in humans over time?
In summary, Nellix is a new concept of treating abdominal aortic aneurysms. There is no proximal and distal fixation, only filling the aneurysm sac with polymer. The major goals is the reduction of endoleaks and reinterventions. Early clinical experience shows promising results. We need to wait for more clinical data.