Proximal neck sealing does not seem to induce neck dilatation

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Endovascular aneurysm repair (EVAR) using proximal polymer sealing does not seem to induce neck dilatation like other endografts, concluded Hence Verhagen (Rotterdam, The Netherlands) during the Aortic Podium 1st session at the 2019 Charing Cross Symposium (CX; 15–18 April, London, UK).

Throughout his talk, Verhagen alluded to an array of studies that illuminate the issue of durability in EVAR. Specifically, he stated: “We know that the most common failure mode of EVAR is loss of proximal seal. This is especially seen in implants in attachment zones that are aneurysmal. So basically, a wide neck is a durability issue for EVAR.”

Taking a global perspective, Verhagen pointed to an international study reported that wide necks evoke a three-fold greater increase in type Ia endoleaks, and a fivefold greater risk  of aneurysm rupture and increased mortality. Moreover, a recent systematic review published this year indicated that sac expansion was 10.07 times more likely in wide neck aneurysm, while rupture was 5.10 times more likely. “All the bad things happen more often in wide neck patients”, Verhagen said.

According to Verhagen, the most common failure mode of EVAR in wide necks was loss of proximal seal due to progressive dilatation of the neck. “So it is not migration, but a progressive dilatation.” As Verhagen and his team found a yearly rate of neck dilatation between 4%–6%, he said: “This continuous outward radial force by self-expandable stent grafts may play an important role here.”

Addressing the CX audience, Verhagen put forward: “There is one different graft from the others; that is the Ovation graft.” Acknowledging that the graft contains a polymer ring that can be filled, he suggested that after implementation, “there is basically no radial force left on the aneurysm neck, leaving no outward force”.

In patients that have been treated so far, Verhagen said that the Ovation graft has demonstrated no dilatation up to five years in the neck—in contrast to most self-expandable stents. “So we thought we would study this subject.”

Thus, Verhagen and his team hypothesised that patients can be treated safely and durably, even with the largest Ovation device (Endologix). A retrospective analysis of six prospectively enrolled studies known as ENCORE (Effectiveness of custom seal with Ovation: Review of the Evidence) included 1,296 patients and had a mean follow-up of three years.

Between the study group and the control, Verhagen reported no difference in all-cause mortality or abdominal aortic aneurysm-related mortality through to five-years. He further said: “We see no difference in rupture; we see no difference in conversion. There is a difference in type Ia endoleak, but in contrast to all the self-expandable stents, these type Ia endoleaks appear on the first postoperative CT, which probably has a lot to do with sizing, more than anything else. After that, there was no type Ia endoleak during the next five years. Proximal reintervention followed the same rule; after 30 days there were no reinterventions for proximal reasons.”

In conclusion, Verhagen argued that endovascular aneurysm repair using proximal polymer sealing does not seem to induce neck dilatation like other endografts. Moreover, in contrast to self-expanding EVAR devices, patients treated with the largest size Ovation do not suffer from more complications compared to standard diameter devices. “So this analysis suggests that Ovation is a durable endovascular aneurysm repair option, even in wide neck anatomy,” surmised Verhagen. He lastly acknowledged that further investigation is needed to understand why Ovation follows a different clinical course.

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