Thomas Nolte, vascular surgeon and director of Vascular Center, Herz und Gefaíößzentrum, Bad Bevensen, Germany, recently commented on the importance of sealing in the endovascular treatment of abdominal aortic aneurysm.
Nolte stated that there is growing evidence that effective sealing in addition with shielding the aortic wall from radial expansive forces results in prevention of endoleak after EVAR. Successful sealing could explain why the aortic neck after endovascular aortic repair (EVAR) with the Ovation (TriVascular) stent graft shows no further expansion, he explained.
The Ovation Prime graft has innovative polymer-filled proximal rings that allow sealing, even in hostile proximal necks. Sealing is achieved by filling customisable O-rings at low pressure.
“Ovation continues to show durable results regarding safety and effectiveness in the treatment of abdominal aortic aneurysm up to three years. Type II endoleaks are not always benign and are usually the reason for aneurysm sac enlargement in this study population,” Nolte told delegates at the Leipzig Interventional Course (LINC; 28–31 January, Leipzig, Germany).
In untreated aneurysms, blood pressure causes a bulge in the aortic wall where the tissue is weak. In self-expanding stent grafts, oversized wire and graft fabric allow the transmission of blood pressure and exert a pressure of their own, Nolte explained. “Blood pressure coupled with outward radial force from the stent contribute to neck dilatation. With the Ovation Prime stent graft, a polymer-filled O-ring insulates the aortic neck from blood pressure resulting in minimal, or no blood pressure and outward radial force from the stent. This could be the explanation why there we see no neck dilatation” he said.
Three years of experience with new approach to sealing
Commenting on the different sealing strategies available, Nolte said that in self-expanding stent grafts, the seal is created by chronic outward force with discontinuous points of wall apposition across a 10–15mm length. “The chronic outward radial force from the stent may result in aortic neck dilatation at the nominal diameter of the stent. The Ovation prime stent graft has a water-tight seal created by the O-ring that provides uniform continuous wall apposition. The non-expansive circumferential apposition from the sealing ring creates no chronic outward radial force and no aortic neck dilatation.”
The Ovation global pivotal study set out to evaluate the safety and effectiveness of the Ovation abdominal stent graft system, with the primary safety endpoint defined as major adverse events within 30 days of the procedure, as determined by the clinical events committee. The primary effectiveness endpoint was defined as a composite of successful delivery and deployment; freedom from rupture and conversion to open surgical repair, and freedom from type I and III endoleak, migration and sac enlargement as determined by an independent core lab. “The follow-up has been scheduled for one and six months and thereafter annually to five years,” Nolte said.
Data from the study showed that patients treated with the Ovation system had no neck dilatation and no late type I endoleak at two years.
In terms of technical success, there were no type I and III endoleak at two years, no migration, no rupture of the aneurysm and no conversion to open repair to two years. In terms of the aneurysm assessment, 3.8% had enlarged more than 5mm at two years. In all those cases type II endoleaks were the driving forces, Nolte said. There was no change in 55.4% of aneurysms at two years and 40.8% had reduced in size at two years.
The European study of 30 patients showed that there were three (10%) major adverse events at one year with no device-related adverse events. There were no cases of type I, III and IV endoleak at three years and no aneurysm rupture, migration or conversion to open repair in the same time frame.