CHICAGO (FRONTLINE MEDICAL NEWS) – Real-world experience with novel endografts like the Ovation Prime abdominal endograft system is prompting some vascular specialists to rethink such central abdominal aortic aneurysm tenets as aortic neck dilation and minimum neck size.

“We started using this in our worst cases, patients with small caliber access vessels and very short aortic necks, to test this device, but over time we’ve pretty much made this our workhorse graft based on our outcomes,” Dr. Syed Hussain of the University of Illinois at Champaign-Urbana, said at a vascular surgery symposium sponsored by Northwestern University.

Among 67 patients with AAAs treated since the team’s first implant in November 2012, the technical success rate is 100%. At baseline, 35% of patients had access vessels < 7 mm, 45% had short aortic neck (< 15 mm), 60% had moderate to severe calcification (> 25% circumferential), and half had moderate to severe thrombus (> 25% circumferential).

The Ovation Prime (TriVascular Technologies) device is relatively quick and easy to put in, with an average procedure time of only 33 minutes, he said. Access was percutaneous in 27%, average blood loss was minimal at 60 mL, and average hospital stay was 1.7 days.

Two patients with severe comorbidities were admitted to the ICU and two patients experienced intraoperative type 1a endoleaks, both successfully treated with a Palmaz stent.

After an average follow-up of 12 months, there have been no type 1, III or IV endoleaks, graft migration, aneurysm enlargement, conversions, ruptures, limb occlusions, or secondary procedures, said Dr. Hussain, who disclosed serving as a consultant for Trivascular and national principal investigator of the PostMarket Ovation Trial . There were 12 type II endoleaks (17%) and all have been clinically irrelevant.

Because of the Ovation’s novel O-ring sealing mechanism, “you get a pretty watertight seal ring on these patients,” he said. More importantly, shear stress is distributed evenly along the entire O-ring, which creates very minimal outward stress on the aorta, “maybe 2 or 3 atmospheres at best.”

Evidence continues to build that self-expandable stents place chronic outward stress on the aorta that causes degeneration of the aortic wall, resulting in eventual aortic neck dilation and endograft migration. While it’s been argued that disease progression leads to aortic dilation, the phenomenon took off after the arrival of endovascular stents, not during decades of open AAA repair, Dr. Hussain, also of the Vein & Vascular Center at the Christie Clinic in Champaign, said.

In the Ovation approval trial, proximal neck dilation at 2 years followed a similar curve in the Ovation and open repair cohorts, compared with those for the more traditional endografts, he noted.

The Ovation Prime system was approved in 2012 and in mid-2014, the Food and Drug Administration approved changes to the indication statement that eliminated the requirement for a minimal aortic neck length.

Essentially, the Ovation device can be placed in any patient if the diameter at 13 mm below the lowest renal artery (the site of the most proximal sealing ring) is within the treatable diameter range of the device (15.8 mm-30.4 mm), Dr. Hussain said.

“The idea of having a neck length is completely starting to go away,” he said. “And even though the trial by Endologix is looking at 1 centimeter as the current requirement for enrolling patients, I think eventually it’s going to get to the point where you’re not going to need a neck for the Nellix device either. You’re going to be able to treat patients who have very short, 1 to 2 millimeter necks, basically perirenal aneurysms, and get a seal on.”

The Nellix endovascular aneurysm sealing system (Endologix) is not commercially available in the U.S., but is the being evaluated in at least three studies. It consists of dual balloon-expandable end-frames surrounded by polymer-filled endobags and is designed to completely fill and seal the aortic aneurysm sac. Anatomical requirements for patients to be enrolled in clinical studies include a nonaneurysmal aortic neck length of ≥ 10 mm, nonaneurysmal aortic neck diameter of 18 mm-32 mm, maximum aortic blood flow lumen diameter of ≤ 60 mm, and common iliac artery diameter of 8 mm-35 mm, according to the company’s website .