Aneurysm sealing evidence continues to build

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The 12-month results of patients treated with the Nellix system are encouraging for the development of endovascular sealing (EVAS) as the next gold standard treatment, according to Matt Thompson (London, UK), with a low overall endoleak rate and an acceptable reintervention rate.

Thompson told the Charing Cross Symposium (28 April–1 May, London, UK) audience that EVAS “may address some of the issues that we have with long-term durability follow-up with conventional endografts; however, that is all dependent on the long-term results”.

The 12-month results of the EVAS FORWARD Global Registry include data from 300 patients (split into four cohorts) treated at 30 centres, who will be followed-up to five years. The registry was started after about 200 commercial implantations of Nellix, so “this is really quite early on in the experience,” said Thompson. Following a device iteration in 2016, further patients will be enrolled in the registry. In addition, there is an investigational device exemption (IDE) study in the USA that has now finished enrolment of 180 patients and there will be continued access to the device in the centres involved. This all means that there will be “somewhere in the region of 1,000 patients” who are prospectively monitored in a risk-adjudicated registry that will provide evidence for this procedure.

The registry is based on real world experience, and there was no prospective screening of patients, meaning that “it has enrolled quite a number of challenging patients”. The Registry employs independent adverse events adjudication with primary outcomes typical of endovascular aneurysm repair (EVAR) therapy.

The patients were divided into four cohorts. Cohort  1 were patients treated within the instructions for use, with neck length ≥10mm and infrarenal angle ≤60 degrees (n=192, 65%). Cohort 2 had neck length 5–10mm and infrarenal angle 61–90 degrees (n=39, 13%). Cohort 3 included patients with juxtarenal aneurysms—neck length 90 degrees (n=37, 13%), and cohort 4 included patients with ruptured aneurysms and EVAR revisions (n=25, 9%).

Thompson pointed out that the EVAS FORWARD registry is different from other registries (such as the ENGAGE and GREAT registries) as it includes a larger proportion of complex abdominal aortic aneurysms.

There were nine (3.4%) patients who suffered from one or more major adverse events at ≤30 days, including three all-cause deaths (1.1%), all of which were perioperative and related to hospital-acquired pneumonia, aspiration pneumonia or gastrointestinal haemorrhage. There were also nine (2.7%) patients who reported one or more major adverse events at ≥30 days including seven (2.7%) cases of all-cause death—none of these deaths were aneurysm-related.

Thompson reported eight (3%) incident endoleaks at ≤30 days. Six of these were type Ia and six were type Ib with one type II which then resolved. “The message to take out of this is that there is a learning curve to this procedure,” Thompson told the audience, “and we think probably three out of six type Ia were related to low implantation of the device or under filling of the bags”. Four of the type Ia were successfully treated with coil embolisation and the use of Onyx, and two patients remained untreated with a type Ia endoleak. After one month and out to the end of follow-up, four more type 1 endoleaks have been reported, all of which have had a successful secondary intervention.

Thompson showed the audience a comparison between Nellix and the IDE studies of several other devices, showing a comparatively low number of persisting endoleaks at 12 months for Nellix, with a rate of just 0.7%, all of which were type Ia or Ib. The rate of persisting endoleaks in the other six devices varied from 6.9–38.2%. The potential absence of type II endoleaks was, according to Thompson, “one of the attractions of Nellix for many of us, and one that has been realised.”

Three ruptures were reported in the follow-up period. The two remaining patients with untreated type I endoleaks were treated with open conversion or iliac extensions. The third rupture was due to a retroperitoneal haematoma and was treated with an open conversion.

Freedom from all-cause mortality at 30 days was 98.9% (AAA-related, 98.9%) and 96% (AAA-related, 98.9%) at one year. This mortality rate of just 4% is “probably half of what you would expect” seeing as it is a “challenging group”. With regard to all-cause mortality, Thompson recommended that the audience “watch this space”.

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